US2705789A - Traffic actuated control systems - Google Patents

Description

April 5, 1955 J. 1.. BARKER TRAFFIC ACTUATED CONTROL SYSTEMS 5 Sheets-Sheet 1 Filed March 6; 1952 INVENTOR.

JOHN L.BARKER mwaz ATTORNEY wE m 93m om 22:9: .3 ml. 5 mwozu mo April 5, 1955 J. 1.. BARKER TRAFFIC ACTUATED CONTROL SYSTEMS 5 sneaks-sheet 2 Filed March 6, 1952 xEm INVENTOR.

JOHN L.BARKER ATTORNEY INVENTOR. JOHN L. BARKER 3 Sheets-Sheet 3 J. L. BARKER TRAFFIC ACTUATED CONTROL SYSTEMS -3 Bl+V--- Filed March 6, 1952 BY 62.44)? ATTORNEY United States Patent TRAFFIC ACTUATED CONTROL SYSTEMS John L. Barker, Norwalk, (101111., assignor to Eastern Industries, Incorporated, East Norwalk, Comm, a corporation of Delaware Application March 6, 1952, Serial No. 275,147

9 Claims. (Cl. 340-61) This invention relates to traflic actuated control systems or apparatus for use at road intersections and the like and in which traffic control signals are operated by the trafiic on the roads.

The invention is more particularly concerned with apparatus of this type for the control of the right-of-way of traific at road intersections where it is also desired to control the speed of trafiic approaching the intersection by normally displaying a red or stop signal to all of the approaches to the intersection in the absence of approaching trafiic and to introduce a brief time delay before switching to a green or go signal in response to traflic approaching a short distance from the intersection but to provide alternate accord of right-of-way to the intersecting roads when traffic is present on more than one of the conflicting roads.

The invention provides improved apparatus of this type in which a brief time delay is provided before change from red to green for the first car approaching a red signal on either of the roads and provides for the prolonging of the display of the green signal by closely spaced cars approaching the green signal with a maximum time limit to such prolonging of the green signal on either road in case of trafiic waiting on the other road, and also providing a cautionary clearance period upon each change from green to red.

In the preferred form of the invention, the usual red,

yellow or amber, and green signals are provided for each approach to the intersection and trafiic detectors are located for actuation by traflic approaching the intersection some distance in advance in each approach and a control apparatus or controller including timing devices operates the signals under joint control of the timing devices and traflic actuation of the detectors.

Trafiic actuated trafiic control systems are already well known in the prior art, including several forms of apparatus of the traflic actuated type employing a normal red signal condition in the absence of traflic. Some of such prior systems provide a time delay before changing to green in response to actuation by approaching traflic and with a return to all red after a time period of absence r of further actuation or transfer from green on one road to green on the intersecting road in response to actuation on the second road during the green period on the first road. In some of such normal all red prior art systems with which I am familiar the signals return directly from green to red unless substantially continuous traflic is interrupted by the operation of a maximum timer to terminate the green period in response to traffic on the intersecting road, and in case of such maximum limit termination a yellow signal period overlaps the end of the green period or is inserted between the green and the red. In some of such systems a yellow signal appears only on transfer of right of way from one road to waiting trafiic on the intersecting road. In some instances the prior art systems divide the control of the highway for individual treatment of the two approaches on the highway so that the green signal may be given to only one of the two approaches or to both of such approaches concurrently depending upon whether the traflic appears only in one or in both of such approaches.

Examples of different forms of such prior art systems appear in U. S. Patent 2,173,747, issued to Charles Adler, Jr., for Patrol System and U. S. Patent 2,297,683, issued to John L. Barker, for Trafiic Actuated Control Apparatus. Consideration of the operation of such prior systems has indicated the need of an improved system hav- "ice ing a greater uniformity of operating cycle and treatment of the intersecing roads, and providing the safety feature of the usual yellow or cautionary indication following every green period termination, in addition to a brief all red signal stage before the green signal is returned to following traflic on the same road or is transferred to approaching or waiting trafiic on the intersecting road.

The present invention provides an improved system which always includes a brief yellow period followed by an all red period, to complete the sub-cycle of the traflic signal through its usual course of colors green, yellow, red, green for all approaching traffic so as to avoid confusing such trafiic and to treat the two approaches of the highway together and the two approaches of the cross road together also to avoid confusing traflic. The improved apparatus according to the invention includes the additional safety feature of a brief all red secondary clearance period following yellow in each full trafilc cycle of transfer of right of way from one road to the other as well as in the sub-cycle of transfer of green through yellow and red and back to green on the same road while the red signal remains continuously on the intersecting road in the absence of traffic on the latter road.

Apparatus according to the present invention provides for the first time to my knowledge a complete combination of full traffic actuated control of right-of-way at an intersection with the usual uniform sequence of signal colors, together with the safety and speed controlling features of a normal all-red signal indication for the intersecting roads for relatively isolated individual vehicles approaching the intersection under light trafiic conditions when the speed of vehicles approaching a green light may be excessive, and including a red delay period for such approaching vehicles which is separately adjustable for the respective intersecting roads so that such delay period can properly be correlated with the distance to traffic actuating elements in the respective roads so as to accord the green signal a short distance in advance of the intersection for such vehicles proceeding at the desired moderate speed but to delay and consequently slow down vehicles approaching at excessive speed.

The present apparatus is the first to my knowledge to combine the uniform green, yellow, red and direct return to green signal sequence, which is so Widely used in the ordinary trailic signal control at intersections, with a signal system which returns to normal red condition upon each clearance of traffic from the respective roads, as well as to provide such a system on a substantially balanced basis with respect to the intersecting roads so that relatively widely spaced or isolated vehicles approaching on either one of the roads will initiate a brief subcycle of a brief red delay interval followed by a green interval and followed by a yellow interval and return to the normal red condition, and successive such widely spaced vehicles on one of the roads in absence of trafiic on the other road will be able to repeat such sub-cycle, and irrespective of which of the roads such successive vehicles arrive on, but the arrival of vehicles sutficiently closely spaced on the two roads alternately will cause the transfer of right of way back and forth between the two roads in response to such traffic, and the arrival of vehicles in the green interval will prolong the interval within a maximum limit, presenting in each case such uniform trailic signal sequence of colors for all such approaching trafiic.

In the preferred form of the invention the apparatus provides a double clearance period in each cycle or subcycle, in that the yellow signal period is followed by a brief all red signal secondary change or clearance period in returning to the normal all red rest position for transfer of right of way to the opposite road or for return of the right of Way to the same road in response to further trafiic actuation.

The present invention also provides improved apparatus of simplified form for this general type of traflic signal cycle including a speed control feature in combination with the right of way control feature at the intersection of two roads. In this improved form of the controller apparatus a step by step controller is employed in which one step provides the green signal period for one road, a succeeding step provides the yellow clearance period and the minimum all red secondary clearance period for such one road, while the succeeding step provides the all red resting period and the next succeeding step provides the all red delay period, the following steps thereafter providing the green period and yellow and minimum all red clearance periods for the intersecting road. Thus in this improved construction the green periods for the respective intersecting roads are provided in appropriate steps of the controller cycle separate from the normal all red to enable each accord of right or" way to include an initial or traific starting green period as well as a traffic actuated extension of the green period, and such green periods are also followed by separate yellow and all red clearance periods and with separate all red resting and succeeding all red delay steps in the cycle, and with the controller always returning to the all-red resting position as the normal position, the timing in this position being variable in accordance with the presence or absence of traffic and depending upon the conditions of transfer of right-of-way from one of the intersecting roads direct to the other or of the return of right-of-way again to the same road previously having it.

In the preferred form of the invention disclosed, the apparatus is arranged to omit effectively both the red delay periods in the transfer of right-of-way from the cross-road to the highway at the end of the cross-road right-of-way period in the event that a traffic actuation occurs on the highway during such cross-road right-ofway period. This is accomplished by the reduction of the time periods of the all-red delay intervals to a negligible value in such a condition so that following the clearance periods of the cross-road the controller will be operated rapidly through the all-red rest position and the following two alternate all-red delay periods.

Similarly if during the accord of right-of-Way to the highway a traffic actuation is received on the cross-road, the all-red delay interval is omitted in the transfer of right-of-way from the highway to the cross-road at the end of the highway right-of-way period. This is accomplished somewhat differently, however, in the controller because the right-of-way position follows directly after the highway clearance position in the control cycle, whereas in the process of transfer of right-of-way from the crossroad to the highway the all-red rest position and following all-red delay position intervene between the crossroad positions and the highway positions. It will be noted, however, that the effect is essentially the same in each case that in transfer of right-of-way from either road to the other in response to actuation occurring before the end of the right of way period in the first road such transfer will include the double clearance of a yellow period followed by a brief all red period, but will omit the all red delay period.

This apparatus lends itself most favorably to the control of vehicle trafiic at the intersection of a high speed highway and a cross road, with relatively long distance signal visibility, and in which the cross road may also have high speed trafiic and may be equal to or less than the highway in importance or traffic volume.

The apparatus not only provides a speed control effect with normal red signals for all relatively isolated individual approaching vehicles and with a brief red delay interval between actuation of the system by such vehicles at a distance from the intersection and the accord of the green signal before the arrival of the vehicle at the intersection, and with a yellow signal period in returning to red, but also depending on traific conditions transfers right-of-way from the highway to the cross road and from the cross road to the highway for time periods variable between minimum and maximum limits respectively in response to traffic actuation in the respective roads as the traflic becomes sufficiently closely spaced, so that as the traflic becomes heavier the system operates in a manner similar to a normal fully traffic actuated signal system for two intersecting roads.

Summarizing the operation of the apparatus for various traffic conditions, under conditions of no trafiic on any of the approaches all of the signal lights will show red. Actuation on either of the highway approaches will, if the vehicle is traveling at the proper speed, cause the signals on the highway to change from red to green shortly before the vehicle arrives at the stop line or edge of the intersection. The green light will remain until the vehicle has entered the intersection at which time the signal will change from green back to red, with a brief intervening yellow clearance period. Another vehicle on the highway, crossing the detector during the first vehicles green period will be given another green interval commencing at the moment of actuation. This feature allows trafiic, which is traveling at the proper rate of speed and at close spacing between cars, to extend the green light indefinately if there have been no vehicles on the cross road.

Vehicles crossing the cross road detector on either of the cross road approaches will put in a call for the rightof-way in a manner similar to the actuation by a vehicle on the highway as described above. Thus upon such cross road actuation if there is no traflic using the highway the controller will be in the normal all red condition and the cross road actuation will if the vehicle is traveling at the proper speed, cause the signals on the cross road to change from red to green shortly before the cross road vehicle arrives at the stop line or edge of the intersection, with such green signal remaining until the vehicle has entered the intersection at which time the signal will change from green back to red with a brief intervening yellow clearance period. Further vehicles on the cross road will be able to extend the green signal period by actuating the controller within the green signal period, as described above in the case of the highway.

If either one or both of the highway approaches have trafiic continuously extending the green signal, the controller begins a highway maximum timing period when a vehicle crosses one of the cross road detectors. This timing period determines the maximum waiting time for the cross road traffic at the expiration of which the right of way will automatically be transferred from the highway to the cross road. During this cross road waiting time before such maximum limit, if the traflic ceases on the highway, the right-of-way will be assigned immediately to the crossroad, following yellow and subsequent all red clearance periods.

The cross road right-of-way period can be extended by vehicles up to a maximum also in the usual manner, the maximum timing beginning with the first actuation on the highway during the cross road green period. The cross road right-of-way is followed by the customary clearing period with the cross road signals changing from green to yellow and then to all red.

At each appearance of the green signal for either the cross road or the highway, an initial green interval is provided for standing traffic to get into motion, and then an extendable green or vehicle interval is provided, without interruption of the green signal.

The controller is so arranged that it automatically returns to its position of normal all red signals in the absence of trafiic on the intersecting roads and it is arranged to be operated out of this position through one or the other of two separately adjustable red delay timing periods in response to actuation on one alone or the other alone of the respective roads or in response to actuation on one road immediately before actuation on the other.

The controller provides separate positions in a cycle of positions to accord right-of-way to the respective roads and the normal rest position of the controller is in a further step of the cycle intermediate the positions for the respective right of way periods. Thus the controller can respond properly to spaced or substantially simultaneous actuations, and in the latter case accords right of way first to the road coming next in the cycle of positions, followed by accord of right of way to the other road, with the termination of each right of way period havlng a yellow clearance period followed by a return to a brief all-red period before the next accord or transfer of right of way.

The controller can yield to the cross road immediately if the highway approach signals are red and there is no traffic on either of the highway approaches, so it is possible for the controller to return the right of way to further cross road traffic immediately after a red delay interval serving to control the speed of such cross road trafiic. Under conditions where the controller is showing the green light to the cross road and it changes to the customary cross road clearing interval with no cars on the highway, another vehicle approaching on the cross road will now cause the controller to go from the cross road yellow to red for only a short delay interval and then immediately back to cross road green again. This process can be repeated until such time as the controller moves to cross road yellow and there is traflic waiting or arriving on the highway in which case it resumes its functions as a normal traflic controller assigning the right of way alternately to the highway and cross road in accordance with trafiic demands on both roads.

It is an object of the invention to provide improved apparatus to combine speed control and right of way control for trafiic at a road intersection to include hold ing a red or stop signal for a brief delay before changing to a green or go signal for widely spaced vehicles approaching the red signal and to prolong the green signal by closely spaced vehicles approaching the green si a1.

ii. is a further object of the invention to provide traflic control apparatus of this character having a brief yellow change signal indication on each change of green to red and providing a rest position in its cycle in neutral relationship to the green periods or positions in respect to the intersecting roads and in which rest position red signals are displayed to all intersecting roads.

It is also an object of the invention to provide a trafiic control apparatus of this character in which a yellow change signal indication is provided on each change of green to red and in which an all red signal indication follows each such yellow signal indication and in which the red delay period for return to green in response to traffic actuation is separately adjustable for each of the roads.

It is an additional object of the invention to provide a trafiic control apparatus of this character in which a yellow change signal indication is provided on each road alone, on each change of green to red, on such road and in which a minimum brief all red signal indication follows each such yellow signal indication and in which the red delay period for return to green is provided in addition to such minimum all red indication and is separately adjustable for each of the roads and is provided in response to relatively isolated widely spaced vehicles in the respective roads but is omitted effectively on each transfer of right of way from one road to another in response to waiting traflic on such other roads.

Reference may be had to the accompanying drawings illustrating the preferred embodiment of the invention and in which:

Fig. 1 shows a layout of apparatus such as may be employed at an intersection in accordance with the invention.

Figs. 2, 3 and 4 combined show a schematic wiring diagram of one form of traffic actuated control apparatus in accordance with the invention including connections with the traffic detectors and the trafiic signals. Figs. 2, 3 and 4 are arranged to be placed one above the other in order with Fig. 2 at the top and Fig. 4 at the bottom to provide the complete circuit diagram.

Referring now to Fig. 1 there is illustrated an intersection of a highway A and a cross road B. A tratfic signal SG is shown in position to display signals to both roads, and will preferably include the usual red, yellow and green signals for each of the roads A and B. Traffic detectors DA1 and DA2 are located on the two approaches respectively of a highway A at some distance from the intersection to be actuated by approaching traffic and detectors DB1 and DB2 are similarly located on the approaches of the cross road B. The detectors and signal are connected to the controller CT as indicated schematically.

Referring now to Fig. 2, 3 and 4 the apparatus is indicated schematically including the controller with its internal Wiring and its connections to the signals and detectors. The controller includes a step-by-step cyclic switching unit which is preferably but not necessarily of the camshaft type. In the present embodiment this cyclic switch unit has a cycle of six camshaft positions numbered 1 to 6 as indicated schematically in the camshaft position diagram at the right of the figures and including the cam operated contacts CIA to C20A, C18 to CSB, and C813 to 0103 inclusive arranged along the right side of the figures. The respective cam contacts are closed in the positions indicated by the black bar or dot in the camshaft position diagram opposite the contacts.

The camshaft is stepped from one position to another by a solenoid or electromagnet S in accordance with familiar practice through a ratchet mechanism not shown.

The camshaft remains at rest in one position until the solenoid is operated to step it immediately to the next position in the cycle.

The apparatus is ordinarily supplied from alternating current power supply wires including the power wire indicated by plus in a circle and extending along the left side of the Figs. 2 and 3 and the grounded return wire indicated by minus in a circle and square and extending along the right side of the figures.

Several timing elements are employed in the controller to time the various signal periods subject to control by the trafiic detectors in certain camshaft positions, and in the present preferred embodiment these timing elements are of the type employing the charging of a condenser through a resistance to the threshold breakdown or conduction voltage of a gaseous discharge tube, the condenser then immediately discharging through the tube to operate a relay indicating the termination of the time period.

Two such condenser discharge tube and relay groups are used as timing units in the present apparatus with various adjustable resistances connected to the several timing circuits by the camshaft contacts in different positions of the camshaft and by relay contacts in different relay combinations as will be subsequently described. Thus the two condenser timing units are employed for a much larger number of different time periods.

The two timing units can be identified by their discharge tubes FA and PB in the figures. Tube FA has an associated condenser KA and relays AS and CS; tube PB has an associated condenser KB and relay BS.

The several resistances controlling the charging rate and consequently controlling the timing are shown schematically near the left side of Figs. 3 and 4.

Direct current power supply is provided for the timing units, employing a common negative line 11 at the right side of the figure in Figs. 2, 3 and 4 and employing a separate positive line 13 indicated by a plus in a square and extending along the left side of Fig. 4 and the lower part of Fig. 3. This direct current supply may be obtained by a transformer and rectifier arrangement from the AC line for example. The operation of the signals through their control cycle is provided by the operation of a number of relays partly controlled by and partly controlling the several timing circuits as operated by the various cam contacts in the several positions of the camshaft, and these relays in some instances provide for two separate timing periods in single positions of the cam shaft as will subsequently appear in this description.

The circuit diagram is arranged in general in across the line from between the lines of the power sources, the several relay coils being shown in block form with the letters inside the block designating the relay. The contacts associated with the respective relays are arranged either below or above the relay coil or both and the operative connection with the coil to the contacts is shown by a vertical dotted line extending from the coil to the several contacts. The contacts bear the relay letter code designation also. In some instances where the relay coil appears on one of the several sheets of drawings comprising the circuit diagram and its contacts appear on another sheet the relay coil is repeated in phantom on the latter sheet by means of a dotted outline of the coil and letter designations for convenience of reference.

The contacts S6 and S8 associated with the solenoid S are operated near the end of the energizing stroke of the solenoid and ratchet mechanism and contact S12 is operated near the beginning of such energizing stroke, with the cam-shaft advanced on the return stroke in the pre ferred form shown.

The two approaches of the highway are served by the red, yellow and green signals AR, AY and AG respectively, and the cross road approaches are served by the red, yellow and green signals BR, BY and BG, respectively shown in Fig. 2. The highway signals are controlled in general by the contacts of the relays AYLR and AGR and the cross road signals are controlled in general by the contacts of the relays BYLR and BGR, these relays being in turn controlled in general by the camshaft contacts and the timing circuits and other relays in response to traffic actuation.

The tralfic detectors DA1 and DA2 for the two approaches respectively of the highway and the detectors DB1 and DB2 for the two approaches of the cross road are indicated schematically in the Fig. 2 as switches, although it will be appreciated that these detectors may take any of a number of well known forms. in the present embodiment the respective switches are closed momentarily by passage of a vehicle over the respective detectors. These detectors are located about 150 feet to 400 feet from the intersection depending on the general speeg of trafiic with the greater distance for the higher spee The detectors DA1 and DAZ control the relay AD, in response to trafic actuations on the highway A and the detectors DB1 and DB2 control the relay B9 in response to trafiic actuations on the cross road B.

Considering now the cycle of operation of the controller it will be noted that the camshaft has a cycle of 6 positions as indicated in the camshaft diagram at the right of the Figs. 2, 3 and 4, including the positions 1 and 2 for the A green and A clearance intervals respectively for the highway and designated AH-V and AYC+ ARC, positions 3 and 4 for the B green and B clearance intervals for the cross road and designated BI+V and BYC+BRC, and positions 5 and 6 for the all red rest position and all red delay intervals designated R1 and ARD-i-BRD respectively.

In the preferred form of the invention illustrated the controller divides several of the camshaft positions into two successive timing periods by means of relays in conjunction with the timing circuit. Thus in positions 1 and 3 the green interval is in each case divided into an initial interval and a following vehicle interval, the A and B clearance intervals are also each divided into two intervals comprising a yellow clearance period followed by a red clearance period, the yellow signal appearing only on the road losing the right of way, and the red appearing thereafter on such road while the red signal remains on the other road.

Two alternative all red intervals are provided for, one in position 6 and the other in position 2 as will subsequently appear, so that a separately adjustable red delay interval may be had before the green for each of the respective roads, the controller passing rapidly through one or the other of these intervals and thus leaving the remaining all red delay interval to be effective, the interval so eifective being automatically selected in accordance with the conditions of the relays in response to traflic actuation determining whether the controller is about to accord right of way to the highway or to the cross road.

Let 1t now be assumed that the camshaft is resting in the all red position 5 in absence of any traiiic actuation s position because of the normally open relay contact AYR and the cam contact C4A being open in position 5. The cross road red signal BR is also energized by the normally closed contacts BGRotl of relay BGR across the AC power wires, the relay BGR also being deenergized in this position by the normally open relay contacts BYR10 and cam contact CSA open in this position. The AY and AG signals are not illuminated in this position because of the normally open relay contact AGR6 in common with their circuits and similarly the signals BY and BG are not illuminated because of the normally open relay contact BGR6 in common with their circuit.

In the condition of the absence of actuation on either road assumed the relays AD and BD controlled by the trafl'ic detectors on highway A and cross road B respectively will also be deenergized as shown in the circuit diagram. The relays IVR, GYR and IR will also be in deenergized condition, as will also relays AY R, BYR and CYR as will subsequently be explained.

The solenoid S and the time period terminating relays AS, BS and CS are also all deenergized in the condition assumed in the rest position.

Thus in the normal all red rest position in the absence of traffic actuation the red signals for both intersecting roads will be operated only and all of the relays in the controller will be in deenergized position.

In the condition assumed a charging circuit is completed for the condenser KA of the A timing circuit from the DC positive power lead 13 via wire is, resistance RX, wire 121, cam contact C3B, wire 31 to the positive side of condenser KA, the negative side being connected via the low limiting resistance RKA to the negative power wire 11. The resistance RX is chosen to be of correct value in relation to the size of the condenser KA and the voltage of the DC power supply to charge condenser KA to the threshold discharge voltage of the discharge tube FA in a very short period of the order of one second for example. However in the absence of traffic assumed, the discharge circuit through the tube FA is open at the contacts AD10 and BD10 of the relays AD and BD respectively controlled by traffic actuation on the respective roads A and B, as will be described more fully below. Thus the condenser KA is quickly charged above the threshold discharge voltage of tube FA and is ready to discharge through tube FA and relay CS as soon as a trafiic actuation occurs to operate either relay AD or relay BD, but in the continued absence of actuation the controller rests in this condition ready to respond to such actuation.

Let it now be assumed that a vehicle arrives on the highway actuating detector DA1 or detector DA2. Actuation of detector DA1 for example closes the detector switch DA1 thus connecting the A. C. negative power line 11 through switch DA1 via wire 14 to the coil of relay AD, the other side of this coil being connected to the positive A. C. power line 12. This energizes relay AD to attract its armatures and to close its normally open or make contacts and open its normally closed or break contacts. Relay AD locks up energized over a holding circuit from the right side of its coil via the make contact AD6 now closed and via wire 17 and cam contacts CSB closed in this camshaft position 5 to negative A. C. power.

Such energization of relay AD also closes its contact AD10 mentioned above to complete a discharge circuit for condenser KA via tube FA and relay CS as follows. This discharge circuit extends from the plus side of condenser KA via wires 18 and 19, tube FA, wire 21, the normally closed break contact IVRSO of relay IVR, wires 23 and 25, break contact A880 of relay AS, wire 26, relay CS, wire 27, the now closed contact AD10 of relay AD, wire 28 and cam contact C9A closed in position 5 to A. C. negative power, the other side of condenser KA being also connected to negative power via the resistor RKA as a current limiting resistor.

Thus with this circuit completed, condenser KA will discharge through tube FA and relay CS to energize the latter which will thus close its make contact C812 which in turn will complete a circuit from negative A. C. power to the right side of the coil of solenoid S, the left side being already connected to the A. C. positive power line 12 thus energizing this solenoid. Operation of solenoid S closes its make contact S6 to complete a quick discharge circuit for condenser KA via wires 31, 32, 33, solenoid contact S6, wire 34, break contact BYR of relay BYR and wire 35 to negative power, thus rapidly completing the discharge of condenser KA through the current limiting resistance RKA.

As soon as the condenser KA is so discharged relay CS is deenergized and tube FA resumes its normally nonconducting condition below its discharge voltage, its initial or threshold discharge voltage being normally considerably higher than its cut-off voltage on discharge. The release of relay CS also releases solenoid S by the reopening of contact C812 and the camshaft is advanced from position 5 to position 6.

In position6 relay CYR is energized via wire 36, cam contact C13A, wire 37, make before break contact ]R8JR800 and wire 38 to negative power, the contact JR8-JR800 being normally closed with relay JR deenergized, and the other side of the coil of relay CYR being connected to positive power. Energization of relay CYR closes its contact CYR22 to complete a charging circuit for condenser KA via the adjustable resistance ARD for timing the red delay period for road A before the transfer to green on this road. This charging circuit extends from KA via wires 31, 32 and 41, make contact CYR22, break contact GYR260 of relay GYR, adjustable resistance ARD and fixed resistance R1 to D. C. positive power wire 13.

In this position 6 the red signals AR and BR remain energized as previously described and the remaining signals stay deenergized as previously described. Thus the charging of condenser KA via resistance ARD starts timing a brief red delay interval for controlling the speed of the vehicle on approach Al, the red delay interval being timed by adjustment of the resistance ARD so that if the vehicle is travelling faster than a desired speed the vehicle will arrive near the stop line near the edge of the intersection while the signal is still red and will therefore be forced to stop or slow down to avoid violating a signal, but if the vehicle is travelling at not more than the desired speed it will receive a green signal shortly before arriving near the stop line.

When condenser KA becomes charged to the threshold voltage of the discharge tube FA this tube becomes conducting and condenser KA discharges through the tube and the relay AS to energize relay AS to complete the red delay timing interval. The discharge circuit through AS extends from KA via wires 18, 19, tube FA, wire 21, make contact IVRS of relay IVR, break contact GYR80, wire 43, wire 44 through AS to negative power. Relay AS closes its contact AS6 to shunt tube FA with low resistance R3 to assure the full discharge of the condenser KA through AS. Energization of relay AS also closes its contact A810 to complete a circuit for energization of relay GYR to negative power via cam contact C11A, wire 47, contact AS10, wire 46 to relay GYR, to relay GYR then locking up over its make contact GYR6, wires 48 and 47 and cam contact C11A, the opposite side of relay GYR being connected to positive A. C. power.

A new rapid charging circuit is now completed for condenser KA via wires 31, 32 and 41, make contact CYR22 and a now closed contact GYR26, wire 51, break contact PR180, wire 52 and the low resistance R2 to the positive D. C. power wire 13. This charges condenser KA in a fraction of a second to the threshold voltage of tube FA which becomes conducting to discharge condenser KA at this time through relay CS to operate the latter, this discharge circuit for KA extending through FA and IVRS as previously described but now extending through the closed make contact GYRS, wire 25, break contact A580, wire 26 through relay CS and cam contact C10A to energize CS. Relay CS closes its contact CS6 to shunt the FA tube circuit via the low resistance R3 to assure the full discharge of the condenser KA through CS. Such energization of relay CS closes its contact C512 to energize solenoid S momentarily as previously described to step the camshaft from position 6 to position 1.

We now have the road A red signal AR deenergized and the A green signal AG energized by the opening of break contact AGR60 and closing of make contact AGR6 respectively because of the energization of relay AGR in this position by the closing of the cam contact C4A, the AG signal being energized via the break contact AYLR60 and make contact AGR6 to the positive power wire 12.

With the closing of the cam contact C4A the relay AGR is energized from A. C. positive power via wire 55, break contact BGR60, wires 56, 57 relay AGR, wires 58, 59, cam contact C4A, wires 61, 62 and break contact IR160, wires 64, 65, break contact GYR100 and wire 66 to negative power. The red signal BR on road B remains deenergized as before.

We now have the right of way accorded to the highway A with the relay IVR energized, this relay IVR having been energized by the closure of the solenoid contact S12 momentarily in stepping from position to position 6, and held energized in position 6 by the closure of cam contact CB, the relay IVR now remaining energized in position 1 through the holding circu1t of its lock-up contact IVR6, wire 67, break contact AS120 of relay AS to negative power.

A new charging circuit is now completed for condenser KA via the adjusting resistance Al for the initial or starting green interval for highway A. This charg 1ng c1rcu1t extends from D. C. positive power, via ad usting resistance AI, make contact IVR22 of energized relay IVR, wire 68, cam contact C113, wires 71, 72 and 18 to the positive side of condenser KA.

After a few seconds time determined by the setting of the adjusting resistance A1 condenser KA will be charged to the threshold voltage of tube FA which will thereupon become conducting to provide a discharging circuit for KA via FA and make contact IVRS and break contact GYRSO as previously traced through relay AS to energize relay AS momentarily. The consequent momentary opening of the break contact AS120 will open the holding circuit of relay IVR to release this relay, while the cam shaft remains in position 1 and the signals remain green on highway A and red on cross road B.

The release of relay IVR however terminates the A initial green period and begins the A vehicle green period which is extendable by vehicle actuated reset as will now be explained. The release of relay IVR completed a new timing circuit via the adjustable resistance AV for charging the condenser KA, this circuit extending from positive power via resistance AV, via break contact IVR220, wire 68 and cam contact 01B and then continuing as before to condenser KA.

If no vehicle arrives and consequently no actuation of the detectors on highway A occurs during the timing of this interval the condenser KA will be charged after a few seconds to the threshold discharge voltage of tube FA which will provide a discharging circuit for condenser KA as previously traced via the break contact IVR30 through relay CS and thence to negative power via cam contact C7A to energize relay CS momentarily to energize solenoid S momentarily by contact CS12 as previously described, the relay CS and the solenoid S then becoming deenergized and the camshaft being stepped by the operation of the solenoid S from position 1 to position 2 in which the highway yellow signal AY will be displayed in place of the green signal AG, by the opening of break contact AYLR60 and the closing of make contact AYLR6, the AYLR relay being energized in this position via con- Lacit AYR12 of relay AYR as will be more fully described e ow.

Such shift from the A vehicle green period to the A yellow change period can be deferred however by the actuation of either of the detector switches DA1 or DA2 during this A vehicle green period, to prolong such period. Such actuation of detector switch DA1 for example closes the circuit to energze relay AD momentarily as the vehicle passes over the detector, and the consequent closure of relay make contact AD8 will close a circuit from negative power via make contact ADS, wire 73, cam contact CIA, wire 74, low resistance RSA to the charging circuit previously traced for condenser KA at the connection between adjusting resistance AV and contact IVR220, thus discharging condenser KA momentarily by such momentary trafiic actuation to reset the timing of this vehicle interval.

If vehicles should continue to arrive on the highway at closer time spacing than the vehicle interval time, they would continue to reset and prolong the time the controller remains in this interval according right of way to the highway. This continued extension of the highway green period could go on indefinitely with continued highway tratfic in the absence of any traific actuation on the cross road. However, if a vehicle arrives on the cross road during this highway green period, or since the traific actuation on highway A in position 5, the closure of one of the detector switches DB1 or DB2 will energize relay BD to start a maximum timing circuit by the charging of condenser KB as will now be described. The closure of one of the detector switches DB1 or DB2 connects negative AC power to the relay BD the other side of this relay being connected to AC positive power, and the consequent energization of relay BD locks up this relay over its make contact BD6 and cam contact C9B to negative power. Energization of relay BD also closes its make contact BD24 which closes a charging circuit for condenser KB via the maximum timing adjusting resistor AMX to initiate a relatively long maximum timing period. This charging circuit extends from DC positive power via adjusting resistor AMX, make contact BD24, wire 81 and cam contact C16A to the positive side of condenser KB, the negative side being returned via the current limiting resistor RKB to negative power.

If closely spaced vehicles on highway A continue to reset the vehicle interval timer under these conditions up to the maximum time controlled by adjusting resistance AMX the condenser KB will be charged through the threshold discharge voltage of the discharge tube PB which will then become conducting to complete a discharge circuit for condenser KB via tube PB and relay BS thus energizing relay BS, which in turn will close its make contact BS12 to operate the solenoid S. The solenoid S will thus close its make contact S8 to insure quick complete discharge of condenser KB, relay BS thus being operated only momentarily and consequently operating the solenoid only momentarily to shift the camshaft from position 1 to position 2 and thus terminate the highway green period at the maximum interval if this green period has been prolonged to the maximum by continued highway traflic.

The operation of relay BS also closes its contacts BS6 to operate the traflic actuated relay AD directly to assure return of the right of way to the highway to care for any vehicle which may be stopped between the highway detector and the intersection by the operation of the maximum timer. This circuit extends from the right side of relay AD via wires 14, 82, contact BS6 and cam contact C413, wires 83, 84, break contact JR120 to negative, the relay AD locking up over its make contact AD6, wire 85, make contact 1VR12, wires 86, 87 to negative power in position 1 before relay contact BS6 opens, the solenoid contact S12 having energized relay IVR in leaving position 1.

Considering now the operation in the A double change position designated AYC-j-ARC" on the cam position chart, the highway yellow signal AY is energized and the cross road red signal BR is energized and the other signals remain deenei'gized, the AYLR relay being energized in this position by energization by the relay AYR and consequent closing of its make contact AYRiZ in the circuit of relay AYLR. The relay AYR is energized in position 2 by the closing of cam contact C14A in this position, thus completing an energizing circuit from the right side of relay AYR via wire 91, cam contact C14A, wires 92, 37, normally closed contact JR8JR800 and wire 38 to AC negative.

The operation of the controller hereafter in this period or at this point in its cycle depends upon whether there is traffic waiting on B or an actuation on B up to this moment as will be more fully described below. The energization of the relay at this point provides the last opportunity for the controller to decide whether it is next to accord the right of way to the cross road B in response to actuation there or whether it is to skip effectively the cross road B periods because of absence of actuation there.

First let it be assumed that an actuation on cross road B has been received at this point or during the prior highway green period so that the relay BD has been energized and locked up energized. In this case, the JR relay will remain deenergized at this point and the regular timing of the yellow change period for the highway A will start with the closure of the make contact AYR22 of the relay AYR. This connects a new charging circuit from positive DC power via the adjusting resistance A1C, break contact GYR220, wire 93, make contact AYR22, wires 94, 95, 32 and 31 to the positive side of condenser KA.

In a few seconds condenser KA charges to the threshold discharge voltage of tube FA which becomes conducting to complete a discharge circuit via contact IVR3 and contact GYRStl through relay AS as previously described. I

The momentary operation of relay AS closes its contact A510 to energize relay GYR via cam contact C11A to negative power and to lock up relay GYR energized over its make contact GYR6 and cam contact C11A as previously described in connection With the description of operation in position 6.

With relay GYR now energized, its break contact GYR220 is opened and its make contact GYR22 is closed to transfer the charging circuit for KA previously described from the A1C adjusting resistor to the A2C adjusting resistor to control the timing in the second of the two dual change intervals for highway A. Also with energization of relay GYR, the opening of its break contact GYRIOO opens the energizing circuit of relay AGR previously traced by way of contact AYRll) and consequently releases the relay AGR to deenergize the highway yellow signal AY and to energize the highway red signal AR by the opening of the relay contact AGR6 and the closing of relay contact AGR60, thus restoring the signals to all red condition for this second change period or second clearance period for the highway as timed by the adjusting resistor A2C.

When the timing of this second change period is completed by the charging of the condenser KA to the threshold voltage of tube PA, the condenser KA is discharged this time through tube PA by way of the closed make contact GYR8 and relay CS, which as previously described will operate relay CS to operate the solenoid S momentarily to shift the camshaft to position 3. The timing of this second change interval will ordinarily be of the order of 1 or 2 seconds for ordinary intersecsections but in some cases will be made somewhat longer for wide intersections or the like where a longer time is required to cross the intersection or clear it.

The controller is now in position 3 according the right of way to the cross road B, this position providing the initial and vehicle intervals for this road identified as BI+V in the camshaft position chart.

In this position 3 the A red signal AR remains energized over the break contact AGR60, and the green and yellow signals AG and AY remain deenergized because of the open contact AGR6. However, the B green signal is energized via the break contact BYLR60 and make contact BGR6 whereas the B red signal BR is deenergized by the opening of the break contact BGR60, the relay BGR being energized in this position via circuit from the AC positive power wire, via break contact AGR60, relay BGR, wire 96, cam contact C5A, wire 62, break contact JR160, wires 64, 65, break contact GYR100, wire 66 to negative power.

In coming into this position initially the relay IVR is held energized over its lock up circuit via its contacts lVR6 and break contact AS120 as previously described for position 1, the relay IVR having previously been energized in entering position 2 and throughout and now therefore remaining energized over its lock up circuit initially in position 3.

A new charging circuit for condenser KA is now completed for the adjusting resistance BI to time the initial interval for cross road B in the green period. This charging circuit extends from DC positive power via resistance BI, make contact IVR24, Wire 98, cam contact C2B, wires 72 and 18 to condenser KA. At the end of a few seconds for timing this initial green interval, condenser KA will be charged to render tube FA conducting as previously described to provide a discharge circuit via this tube and IVR8 and GYRSO to operate relay AS.

The operation of relay AS will interrupt the holding circuit for relay IVR at contact AS120 here as similarly described in the case of position 1, and the relay IVR is thus released to terminate the initial interval and start the timing of the vehicle interval for the cross road B as controlled by the adjusting resistance BV. Thus the release of relay IVR opens its make contact IVR24 to disconnect the adjusting resistance BI and to connect the adjusting resistance BV from positive power by way of the break contact now closed IVR240 and cam contact C2B previously described to provide a charging circuit for condenser KA.

If there is no further actuation on the cross road B during this interval, the interval will be completed directly after a few seconds by the condenser KA being sufiiciently charged to render tube FA conducting and thus to discharge through relay CS to operate the solenoid to step the camshaft into position 4. However, n this position as in the case of position 1, the vehicle interval timing may be reset by vehicles approaching the green signal and thus any actuation of either detector DB1 or DB2 on the cross road during this interval will operate relay BD momentarily and by the closing of contact DB8 will connect a low resistance RSB via wire 99, cam contact C2A, wire and contact DB8 between contact IVR240 and negative power to discharge the condenser to restart its timing as soon as the actuation ceases and relay ED is released again.

Successive vehicles on the cross road B can continue to prolong the B vehicle green interval if they are sufficiently closely spaced to arrive within the timing of this interval as just described, and an actuation on the opposite road, highway A by energizing relay AD and closing its make contact AD26 will establish a maximum timing charging circuit via maximum adjusting resistor BMX, contact AD26, wire 136 and cam shaft contact C17A to charge condenser KB in this interval and-consequently operate relay BS as previously described to operate the solenoid S momentarily to advance the camshaft from position 3 to position 4 in a manner similar to that described previously for the shift of the camshaft from position 1 to position 2.

The operation of relay BS in this connection closes its make contact BS8 to energize relay BD to assure that a call will be left on cross road B for the return of right of way subsequently to care for any vehicle between the detector and the intersection. Such energization of relay BD is by a circuit from the right side of this relay via wires 102, 101, contact BS8, cam contact CSB, wire 84, break contact JR to negative power, the relay locking up energ zed over its make contact BD6 and make contact IVR14 of relay IVR, which is energized at this time by the slightly preceding operation of contact S12 of the solenoid and carries over into position 4 on cam contact CB, the relay BD remaining locked up over its contact DB6 through position 4 and then through positions 5, 6 and 1 over cam contact C9B, and then remaining locked up through position 2 by contact IVR14 again.

Assuming now that the controller has reached position 4 either as a result of completion of the vehicle interval timing and operation of relay CS or by completion of the maximum timing by operation of relay BS and the consequent stepping of the camshaft from position 3 to position 4 in either case, this position 4 provides a double clearance comprising a yellow clearance period followed by a red clearance period for road B and is designated BYC and BRC in the camshaft position chart.

Upon reaching position 4 under the conditions described, the relay BYR is energized by the closing of cam contact C12A which completes a circuit to the right side of relay BYR via wire 105, cam contact C12A, wires 106, 92, 37 and normallyclosed contact JR8]R8130 of relay JR, wire 38 to negative power. At this point in the cycle the operation of the controller depends on the presence or absence of actuation on the respective roads. It the relay AD is energized from an unanswered actuation for example, the relay JR will become energized at this point by a circuit over the make contact AD24 and the make contact BYRS, such circuit being described more fully below. However if there has been no actuation on the highway A since the last accord of right of way there and the relay AD is thus not energized, its contact AD24 will be open and thus prevent energization of relay JR at this point in the cycle.

Assuming for the moment however that there has been no actuation at this point on highway A and that the contact AD24 remains open, the relay JR will not be operated. However the operation of the relay BYR in this position 4 as above described will complete a circuit for energizing the relay BYLR via wire 113, make contact BYR12 to negative power, the other side of relay BYLR being connected to the AC positive power wire 12. This energization of relay BYLR will open its reak contact BYLR60 to deenergize the B green signal BG and will close its contact BYLR6 energize the B yellow signal BY, the red signal AR remaining energized on highway A as before. This signal condition prevails through the timing of the first clearance period for cross road B as controlled by the adjusting resistance B1C.

The charging circuit for this timing period completed by the closing of contact BYR22 extends from the positive side of condenser KA via wires 31, 32, 95, make contact BYRZZ, wire 115, break contact GYR240 of relay GYR, and adjusting resistance B1C to the positive DC power.

As soon as condenser KA has reached the threshold voltage of tube PA the conduction of this tube completes a discharge circuit for condenser KA through relay AS via contacts IVRS and GYRBt) in the same fashion as previously described in connection with position 2. Operation of relay AS closes its make contact AS10 to complete a circuit for energizing relay GYR which locks up over its contact GYR6, as previously described in connection with position 2, and an auxiliary circuit in parallel with cam contact C11A, via wire 47, cam contact CSA, wire 148, contact BYR14 to A. C. negative power. This terminates the first or yellow clearance period for cross road B, and initiates the second or red clearance period for cross road B by the opening of contact GYR240 and by the closing of contact GYR24, which switches the charging circuit for condenser KA at wire 115 previously described, from the adjusting resistance B1C to the adjusting resistance B2C, which now controls the timing of this interval of the order of 1 or 2 seconds or somewhat more for example.

In this second interval BRC in position 4, the signal BY is deenergized and the signal BR is energized by the release or deenergization of relay BGR by the opening of the break contact GYRIOO by energization of relay GYR as previously described, this circuit for relay BGR having previously been described more fully. The deenergization of relay BGR opens its contact BGR6 and closes its contact BGR60 to complete this switching of the B signals from green to red as described.

This second clearance interval of all red for cross road B is now timed via the control resistance B2C and the charging circuit for condenser KA beyond contact BYR22 as previously described, the interval being terminated by the discharge of condenser KA through the tube FA and this time through the contact GYRS and relay CS as previously described in connection with position 2. The consequent energization of relay CS operates the solenoid S momentarily to step the cam shaft from position 4 to position 5, the relay BYR becoming deenergized in leaving position 4 by the opening of the cam contact C12A in the condition of absence of further actuation as assumed, and such deenergization of the relay BYR, by the opening of contact BYR14, along with the opening also of the cam contact C11A in leaving position 4 now deenergizes relay GYR.

We now have in position 5 the relay IVR energized over its lock up contact IVR6 and break contact AS of relay AS, the relay IVR having previously been energized in entering position 4. This position 5 has a direct short period timing charging circuit for condenser KA via cam contact C3B, wire 121, resistance RX, wire 15 to the D. C. positive power wire 13. This provides a very short time period of the order of one second if desired in accordance with the size of resistor chosen for RX, at the end of which timing period condenser KA discharges through tube FA and relay AS over a discharge circuit including contact IVR8 previously traced, and the operation of relay AS consequently opens at contact AS120 the holding circuit for relay IVR to release this relay. The release of relay IVR to its deenergized position opens the contact IVRS and closes the contact IVRSO to transfer the discharge circuit for condenser KA via tube FA to the relay CS, and since the cam contact C3B is still closed to supply the rapid charging circuit for condenser KA via resistor RX as previously described, condenser KA becomes fully charged so as to be ready to terminate this interval as soon as the next trafiic actuation occurs, or in the event that such traffic actuation has now occurred to operate or to energize relay AD or relay BD.

We are now in the original starting position assumed, under the conditions of which in the absence of energization of relay AD or relay BD the contacts AD10 and BD10 will both be open and the discharge circuit via tube FA and relay CS will remain open at these relay contacts until one or the other of the relays is energized by traflic actuation.

We have therefore traced a cycle of operation from the normal all red rest position to accord right of Way to highway A, then to highway B and return to the rest position in response to traflic actuation first on highway A and then within or prior to the highway green period for example a later actuation on cross road B.

It will be recalled that at the time of the shift of the controller from the A green position 1 to the A- clearance position 2 it was previously assumed that relay BD was energized at this point by an actuation on the cross road B. However it will be appreciated that the condition may occur that there may have been only one or more actuations on highway A and no actuation on cross road B, in which case at the termination of the highway green period the controller will be set to skip rapidly through the intervening positions to position 4 without accord of right of way to cross road B, and while holding the yellow signal on highway A and the red signal on cross road B, so that the trafiic signals will go through a sub cycle from all red in position 5 and red delay in position 6 to green on A in position 1 and yellow on A in position 2 and through to position 4 without change, at which point the timing of the yellow signal is completed and the trafiic signals return to red on A while remaining red on B, and then return to the all red rest position 5 while remaining all red, all in response to an actuation on highway A alone.

The accord of right of way to A in response to an actuation on A from the all rest position has previously been described. Let it now be assumed at the arrival in position 2 at the start of the yellow period on A, that there is no further trafiic actuation on A or B and that relays AD and BD are deenergized, showing that there is no unanswered actuation at this point. At this point it will be recalled that the relay AYR is energized over cam contact C14A and the normally closed contact IR8JR800 of relay JR. At this point a circuit is completed for energization of relay JR extending from the right side of relay JR via make contact AYR8, wire 124, break contact BD80 of relay BD to negative power, the other side of relay JR being connected to positive power. Thus relay JR will be energized at this point and will lock up over its make contact JR12 from Wire 124 and the contact AYRS previously described.

Energization of relay JR opens its normally closed contact JR8JR800 but before doing so it closes its contact JR7JR8 since this is a make before break contact assembly as indicated schematically in the drawing. The closing of the make contact JR8 completes a holding circuit for relay AYR from negative power via wire 38, contact JR8JR7, Wires 126, 127, 128, make contact AYR6 of relay AYR, wire 131, cam contact CA, and wire 91 to the right side of relay AYR. Thus relay JR and relay AYR both remain energized in this position and continue to be energized since AYR holding circuit remains completed over the cam contact C20A through positions 2, 3 and 4.

As soon as relay JR becomes energized in position 2 as described a very short period timing circuit is completed from positive D. C. power via wire 132, make contact JR24 of relay JR, low resistance R4, wires 133,

134, make contact AYR24, wire 136 and cam contact 1 C17A, closed in positions 2 and 3, to charge condenser KB very rapidly in a time of the order of a fraction of a second for example. Thus condenser KB will be charged in less than a second to the threshold discharge voltage of tube PB and discharged through this tube then to energize relay BS which in turn will close its contact BS12 to energize the solenoid momentarily to step the camshaft from position 2 to position 3. This very short period timing circuit remains completed over cam contact C17A in position 3 and therefore in less than a second again charges condenser KB to operate relay BS through tube PB and again operate the solenoid S momentarily to step the camshaft into position 4, at which point the cam contact C17A opens to interrupt this very short period timing circuit.

Meanwhile during this rapid stepping operation from position 2 to position 4, the relay AYR has remained energized over its holding circuit as previously described over cam contact C20A to hold relay AYLR energized over the make contact AYR12 of relay AYR, and relay AGR remains energized over the circuit via contact AYR10 and contact GYR100 to negative power as previously described. Thus during this rapid stepping from position 2 to position 4, the signals remain the same with the A yellow signal AY energized and the red signal BR energized as before.

The repeated operation of relay BS in this rapid stepping action does not of itself energize either relay AD or BD however without traffic actuation of these relays since the circuits for energizing the relays AD and BD via the respective contacts BS6 and BS8 both include in common the contact JR120 of relay JR, this latter contact being open and thus rendering the contacts BS6 and BS8 ineffective during this rapid stepping operation.

On arriving in position 4 under these conditions, the

rapid timing circuit for condenser KB has now been opened at cam contact C17A and the normal yellow timing circuit for the first of the dual clearance periods in this position becomes effective via the adjusting resistance A1C, break contact GYR220, wire 93, make contact AYR22, wires 94, 95, 32 and 31 to condenser KA. Thus the regular adjusting resistance timing control for the road A yellow period is effective now in position 4 to time the display of the yellow signal to road A under the conditions described of no actuation on cross road B. if any actuation were to occur on cross road B after the relay JR was energized in position 2 such actuation would be ineffective to interrupt the rapid stepping through the cross road positions to position 4 but would. leave relay BD locked up energized over its contact BD6 and make contact IVR14 of relay IVR energized in position 2 and remaining energized over its lock up contact IVR6 and the contact AS120 of relay AS.

The normal timing of the A yellow period now proceeds over the timing resistor A10 in position 4 and this interval is terminated by condenser KA discharging through tube FA to operate relay AS to close its contact A810 to operate to relay GYR and lock up the latter over its contact GYR6, all as previously described. This energization of relay GYR opens its contact GYRIOO torelease relay AGR and thus deenergize the A yellow signal AY and energize the A red signal AR. Energization of relay GYR also transfers the charging circuit for condenser KA from the adjusting resistance AIG to the adjusting resistance A2C by the opening of contact 16 GYR220 and the closing of contact GYR22 as previously described in connection with position 2, but now effective in position 4 by reason of the continued energization of relay AYR in this position.

The timing of the secondary or red clearance period for highway A will now proceed under the control of adjusting resistor A2C in position 4 and at the end of this time period condenser KA will discharge through tube FA and relay CS to energize the latter since the relay CS has now been connected in circuit with tube FA by the closure of make contact GYRS. Energization of relay CS momentarily energizes solenoid S momentarily to step the camshaft from position 4 to position 5, as previously described. This deenergizes relay AYR with the opening of cam contact C20A in this lock up circuit, which in turn opens the lock up circuit of relay JR at contact AYRS thus deenergizing relay JR. The timing of two successive short periods in the rest position 5 will now proceed via the resistance RX, the first such period with relay IVR in and terminating with the release of relay IVR which starts the second period at the end of the timing of which condenser KA remains charged in absence of actuation, since its discharge circuit via relay AS is maintained open at contact IVRS and its discharge circuit via relay CS is maintained open at the traffic actuated relay contact ADlt} and BD10 until a trafiic actuation occurs, the parallel circuits for relay CS via cam contacts C7A and C10A being open in this position.

Thus with the arrival at the normal resting condition the operation of the controller has been traced through a sub-cycle in response to an actuation on highway A alone, starting through the A red delay period in position 6, the A initial and vehicle green periods in position 1, the A yellow and all red clearance periods starting in position 2 and continuing through the rapid stepping through positions 2 and 3 to position 4 and actually timed in position 4, the stepping from position 2 to 4 occurring during the yellow signal interval, and the controller returning to the rest position 5 with all red being maintained in this position.

Widely spaced vehicles on highway A can repeat this sub-cycle of operation of the A signals providing each such vehicle with a brief red delay period, a green period, a yellow clearance period followed by a red clearance period, with the all red condition continuing in the rest position in absence of further vehicle actuation.

It will now be assumed that starting in the rest con dition in position 5 with condenser KA charged, a vehicle arrives only on the cross road B. This actuation of the detector DB1 for example closes the switch DB1 to energize relay BD from negative power, the relay BD locking up energized over its contact BD6 and cam contact C9B.

Energization of relay BD also closes its contact BD10 to complete a discharge circuit for condenser KA through tube FA and relay CS via cam contact C9A to operate solenoid S and step the camshaft into position 6 as previously described. The relay IVR is energized in going into position 6 and the relay CYR is energized in position 6 by the closure of the cam contact C13A, the circuit for energization of relay CYR extending from its right side via wire 36, cam contact C13A, wire 37, break contact JRSGG-J R8, wire 38 to negative power, the other side of CYR being connected to positive power.

Upon energization of relay CYR, its make contact CYRS closes to complete a circuit for energizing relay JR at this point over a break contact AD which is closed in the absence of actuation on A as assumed. This circuit for relay I R extends from the right side of this relay via wires 107, 109, make contact CYRS, wire 113, break contact AD80 of relay AD, wire 114 to negative power.

As soon as relay IR is energized, it closes a lock up circuit for itself over its make contact JR10 and the make contact CYRS just described, the contact I R10 in effect shunting the contact AD80 so that actuation on A beyond this point will not affect relay 1 R and will not be effective to accord the right of way to highway A until after cross road B has been served in response to its prior actuation.

Energization of relay JR also completes a holding circuit for relay CYR via wire 36, cam contact C19A, make contact CYR6 of relay CYR, wire 126, make contact JR7JRS now closed, and wire 38 to negative power, so that relay CYR is now locked up energized over cam contact C19A through position 6, 1 and 2.

Such energization of relay CYR and relay JR is successive but substantially immediate at the beginning of the all red signal period in position 6, and thus with the actuation only on cross road B, a circuit is now completed in this position via the make contact CYR22 and break contact GYR260, and make contact JR14 shunting the adjusting resistance ARD for quick charging of condenser KA via the low resistance R1. This quick charging circuit for condenser KA at this point extends from positive DC power via the low resistance R1, wire 117, contact JR14, wire 118, contact GYR26!) and contact CYR22, wires 41, 32 and 31 to condenser KA. Thus this condenser is charged quickly in considerably less than one second and with contact GYR80 closed relay AS is connected through tube FA to be energized by the discharge of the condenser KA through this relay and tube. The consequent momentary energization of relay AS closes its contact AS10 momentarily to energize relay GYR which locks up over its contact GYR6 and cam contact C11A in position 6 and position 2.

Meanwhile however a quick charging circuit is completed with the initial energization of relay JR by its make contact JR24 and resistance R4 for condenser KB to operate relay BS and consequently the solenoid S to rapidly step the cam shaft from position 6 to position 1 and from position 1 to position 2 with only a fraction of a second in each step, with the signals being maintained in their all red condition by keeping both relays AGR and BGR deenergized by the break contact JR160 held open by the energized relay JR and by the open contacts AYR10 and BYR10.

The rapid charging circuit for condenser KB for quick stepping as just described extends from positive D. C. power via wire 132, make contact JR24, low resistance R4, wire 133, make contact CYR24, wires 144 and 81, cam contact C16A to condenser KB.

Thus the controller steps rapidly in a total time of the order of one second from position 6 into position 2 at which point the rapid stepping is stopped by the opening of the quick charging circuit for condenser KB at cam contact C16A. In this position 2 relay GYR has been energized and locked up by the quick charging of condenser KA and operation of relay AS as previously described so that a timing circuit is now closed via make contact CYR22 and make contact GYR26 through the B red delay period adjusting resistance BRD and low resistance R2. This charging circuit extends from the D. C. positive power via resistance R2 and adjusting resistance BRD, make contact GYR26, make contact CYR22, wires 41, 32 and 31 to condenser KA, and the red delay interval prior to accord right of way to road B is now timed in this position 2.

On completion of this timing period of a few seconds, condenser KA discharges through tube FA and relay CS and cam contacts C10A for example, the relay CS having been connected in the circuit by the closing of relay contact GYRS as previously described. Operation of relay CS causes operation of solenoid S to step the camshaft from position 2 to position 3 in which the relay CYR releases with the opening of its holding circuit through cam contact C19A. Relay IVR remains energized through its holding circuit via its contact IVR6 and relay contact AS120 at this point to complete a timing circuit via relay contact IVR24 and the B initial green period adusting resistance BI as previously described for position 3.

The green signal is energized and the red signal deenergized for cross road B in this position by the energization of relay BGR as previously described and the timing of the two successive time periods B initial and B vehicle periods with the latter extendable by further trafiic actuation on road B within the B vehicle interval timing period have been described previously in connection with the description of position 3 and now operate in the same manner so that with the assumption that there has only been actuation on the cross road B, the controller will be stepped to the BYC and BRC dual change position 4, as previously described to time successively a yellow period for cross road B followed by a red clearance period for cross road B, and continuing with the assumption that there is no further actuation on B and no actuation on A the controller will be stepped into position 5 and come to rest in this position as previously described.

Therefore a sub-cycle for the controller has now been completed from the all red rest position 5 through an all red delay period timed for cross road B, but in position 2, to accord right of way to the cross road B in position 3 followed by the yellow clearance and red clearance for cross road B in position 4, and then returning to the all red rest position 5, all in response to actuation only on cross road B.

Let it now be assumed that during the cross road B green period or during the preceding yellow period or red clearance period for highway A that there was also a trafiic actuation on highway A. Such tratfic actuation on A may also have occurred in position 2 during the timing of the all red delay period prior to cross road B green it the cross road actuation occurred first during the all red rest condition in position 5. In either case it is assumed that at the time of leaving position 3 and entering position 4 at the end of the green period for cross road B, there has been an unanswered actuation on highway A, and the relay AD will he therefore locked up energized over its contact AD6, wire 85, contact IVR12, wires 86, 87 to negative power in position 2, and position 6 and over its contact AD6 and cam contact C8B to negative power in positions 3, 4 and 5.

Thus at the time of entering position 4, relay BYR will be energized by the closing of cam contact C12A in this position, the energizing circuit extending from the right side of relay BYR via wire 105, cam contact C12A, wires 92, 37, break contact JR800-JR8, wire 38 to negative power. With the present assumption that the-relay AD is energized by an actuation on highway A at or prior to this point, a circuit for energization of relay JR will now be closed at this point via make contact BYRS of relay BYR and the make contact AD24 of relay AD, this circuit extending from the right side of relay JR via wire 107, contact BYRS, wires 108, 111, contact AD24 to negative power. Relay JR locks up energized over its make contact JR6 to negative power as long as contact BYRS remains closed.

The relay BYR is also now provided with a lock up or holding circuit from its right side via wire 105, cam contact C18A closed in positions 4, 5 and 6, wire 141, make contact BYR6, wires 142, 127, 126, make contact JR7JR8 of relay JR, wire 38 to negative power. The relays BYR and JR are therefore both locked up energized over each others contacts under the control of cam contact C18A continuing energized through positions 4, 5 and 6.

A quick charging circuit is thus completed from positive power via wire 132, make contact JR24, low resistance R4, make contact BYR24, wire 143, cam contact C15A closed in positions 4 and 5 to condenser KB. This quick charging circuit charges condenser KB in a fraction of a second to the threshold discharge voltage of tube FB as previously described to operate relay BS which in turn operates solenoid S to step the cam shaft from position 4 to position 5, and in which position condenser KB is immediately recharged through the same timing circuit to again operate relay BS and consequently solenoid S step the camshaft into position 6, at which point the quick charging circuit is opened by the opening of cam contact C15A.

The controller now proceeds to time the yellow clearing period for cross road B as controlled by the adjusting resistance BIC, but this time in position 6, with the relay BYR remaining energized with its make contact BYR22 closed. This charging circuit extends from positive D. C. power via adjusting resistance BIC, relay contact GYR240, wire 115, make contact BYR22, wires 95, 32, 31 to condenser KA to charge the latter to time this interval.

During the rapid stepping from position 4 to position 6 as well as during the timing of this first change interval by the adjusting resistance B1C, the yellow signal has been maintained on the cross road B and the red signal on highway A, the relay BGR having been energized and held energized by the make contact BYR10 of relay BYR, and the relay BYLR having been energized and held energized by the make contact BYRlZ so that the contacts BGR6 and BYLR6 together close the circuit for the signal BY, and the signal BG is maintained deenergized by the open contact BYLR60, the red signal BR being maintained deenergized by the open contact BGR60, and the highway red signal AR being maintained energized by the relay contact AGR60 with relay AGR deenergized also by the open contact BGR60,

On completion of the timing of this first or yellow clearance interval in position 6 over adjusting resistance BIC, condenser KA discharges through tube FA and relay AS which is in circuit with FA through the break contact GYRSO, thus energizing relay AS and closing its contact A510 to energize relay GYR, which locks up over its contact GYR6 over cam contact G11A closed in this position. Such energization of relay GYR opens its contact GYR240 and closes its contact GYR24 to transfer control of the charging circuit for KA previously traced from adjusting resistance BIC to adjusting resistance B2C to time the second change or clearance period for cross road B in which the signals are all red, the signals having been changed from yellow to red on cross road B by the opening of the break contact GYR100 in the circuit of the relay BGR previously traced to deenergize relay BGR and consequently open the latters contact BGR6 in the circuit of the yellow signal BY and closing the contact BGR60 in the circuit of the red signal BR.

On completion of the timing of this second clearance interval over adjusting resistance B2C charging condenser KA this condenser discharges through tube FA and relay CS and cam contact C10A, the relay CS having been placed in the circuit of tube PA by the make contact GYRS being closed with the relay GYR energized as previously described. The consequent energization of relay CS then operates solenoid S to step the camshaft from position 6 to position 1 as previously described, the relay BYR and the relay JR becoming deenergized in this operation by the opening of the holding circuit of relay BYR via cam contact C18A which is now opened. The relay IVR however remains energized from position 6 into position 1 to complete a timing circuit for the A initial interval by the adjusting resistance AI as previously described, and B red signal BR remains energized with BGR deenergized, the A red signal becoming deenergized and the A green signal becoming energized by energization of relay AGR by the closing of cam contact C4A and relay contact JR160 and relay contact GYR100 as the camshaft reaches position 1, the relay GYR having been deenergized by the opening of cam contact C11A in going into position 1.

The controller now continues to operate through the highway A initial green and vehicle interval green periods in the manner previously described in connection with position 1, the controller stepping into position 2 at the termination of timing of the vehicle interval within one vehicle interval time after the last highway A actuation, or by action of the maximum timer if the vehicle interval timer is prevented from completing its timing by closely spaced vehicles on highway A after the arrival of a vehicle on cross road B.

As previously described the controller continues from this position of highway green to the following highway clearance positions and either directly from this position to accord right of way to cross road B in position 3 after timing the highway yellow clearance and the following all red clearance in position 2 if there is a cross road actuation, or continues rapidly through positions 2 and 3 to position 4 to time the two highway clearance intervals if there is no actuation on cross road B.

Thus the controller will continue to accord right of way alternately to the two roads with a yellow clearance period and all red clearance period following each accord of right of way in the transfer of right of way from one road to the other, so long as there is an unanswered actuation on the opposite road at the time of completion of the right of way period, and under such conditions it will be noted that the all red rest period and the all red delay periods are omitted in such transfer of right of way back and forth between the roads. Thus the all red rest periods of position 5 and all red delay periods of position 6 are obviously not involved and thus are effectively omitted in transferring from the A clearance position 2 to the immediately following B green position 3 in according right of way to a waiting vehicle on B, and the all red rest periods of position 5 and all red delay period of position 6 are also effectively omitted in transferring from the B green position 3 through the following positions 4, 5 and 6 providing the yellow and all red clearance periods for cross road B in response to waiting trafiic on highway A, since under these conditions the timing of the all red rest position is substantially eliminated or reduced to substantially negligible value by the quick stepping circuit previously described for condenser KB by the contact JR24 of relay JR, and the red delay timing being prevented by the controlling contact CYR22 remaining open since CYR cannot be energized in position 6 with relay JR energized as the camshaft is stepped into this position, as is the case with an actuation on highway A as the camshaft arrives in position 4.

Thus in transferring right of way from cross road B t highway A in response to waiting vehicles on highway A the all red rest periods and the all red delay periods are effectively eliminated and the regular yellow clearance and following all red clearance periods for the cross road B are timed in position 6 after the camshaft is stepped rapidly from position 4 to position 6.

Thus as has been described, the controller in the absence of traific will normally rest with all red signals displayed in position 5 and will operate through a subcycle of accord of right of way to one of the roads and back to all red through the preliminary all red delay period, then green period, then yellow period and all red clearance period back to all red rest in response to trafiic actuation on such one road alone. Upon a single such actuation, such accord of right of way will include a single green period comprising an initial or starting interval followed by an extendable vehicle interval which may each be a few seconds or several seconds in length for example and together without extension of the vehicle interval comprise a minimum green period in response to single actuation.

If further traflic actuation has occurred by closely spaced vehicles approaching the green signal during the green period however the green period will be extended by reset of the vehicle interval timer by such actuation within a maximum limit brought into play only in response to trafiic actuation on the opposite road as by traffic waiting against the red signal.

It will also be noted that if there is actuation on one road alone and right of way is consequently accorded to such one road and the timing of the vehicle interval is completed to terminate such right of way and shift the controller into the following yellow clearance period, and another traffic actuation occurs on the same road after the yellow clearance period has started the con troller will time the yellow clearance period and the following all red clearance period in return to the all red rest position 5, but will continue without resting to time an all red delay period to repeat the sub-cycle, including accord of right of way again to the same road.-

Thus in shifting to position 2 in terminating rightof way to highway A in response to single actuation there the relay AYR will be energized in this position as previously described over the cam contact C14A and break contact JRSDO of relay JR, and with no actuation on road B as assumed, relay JR will then become energized over the closed make contact AYR8 and the closed break contact BD80, and relays JR and AYR will lock up mutually over cam contact C20A through positions 2, 3 and 4 as previously described. Thus when the camshaft arrives in position 4 through the rapid-stepping action, the relay BYR cannot be energized in this position because of the open break contact JR800 with relay JR energized despite the closed contact AD24 caused by the immediate recurring actuation on highway A as assumed. Thus under these conditions the controller steps to position 5 upon completion of the timing of the yellow and red clearance intervals for highway A in position 4 and continues after the timing of the all red brief rest period in position 5 to then time the red delay period again for highway A in position 6 to reaccord right of way in the next following position 1.

Similarly if at the start of the yellow period of cross road B at the termination of the right of way there in response to actuation and completion of the vehicle interval time, another cross road B actuation now occurs without any actuation having been received on the highway A, the relay BYR will have been energized at the begin ning of this cross road yellow period in position 4 over the break contact JR800 of relay JR and the cam contact C12A as previously described. Since no actuation on road A has been assumed the relay JR will not be energized because of the open contact AD24, and the timing of the cross road yellow and following red clearance intervals will proceed in position 4 as previously described, without relay JR becoming energized, and the controller will then shift to position 5 to time the brief all red rest period without resting however in this position in view of the immediately recurring actuation assumed on cross road B alone, and will thus continue on to position 6 at which point relay CYR will then become energized and without actuation on highway A, the relay J R will become energized to step rapidly to position 2 in which the red delay period before accord of right of way to cross road B will be timed.

It will be noted however that if it is assumed that the right of way has been accorded to cross road B in response to an actuation there alone and such right of way has now terminated and the controller is timing the cross road yellow or red clearance intervals in position 4 and actuation now occurs on highway A for the first time during the timing of either of such intervals, the relay JR will be immediately energized in response to such actuation with the closing of the make contact AD24. Thus if contact AD24 closes at any time during the timing of the yellow clearance interval for cross road B in position 4 the consequent energization of rely JR will start the rapid stepping action previously described from position 4 to position 6 and the timing of the yellow period for cross road B will be continued and completed in position 6 since the condenser KA is not discharged by the solenoid contact S6 during this rapid stepping, because the contact BYR160 is open in series with this circuit. The controller thereupon, at completion of the timing of the yellow period for cross road B in position 6, operates relay AS as previously described to energize and lock up relay GYR to time the all red clearance period for cross road B, at the end of which the relay CS is operated to advance the controller to position 1 to accord right of way in response to the highway A actuation assumed.

It will'be further noted however that if the controller had already completed the timing of the cross road yellow period in position 4 before the closing of contact AD24 by highway A actuation, the relay GYR would already have been energized by the operation of relay AS closing its contact A510 in this position. Thus when the relay JR is energized with the closing of contact AD24 the rapid stepping action produced by the closing of contact 1 R24 will occur during the all red clearance period with relay GYR locked up energized and the signals remaining all red while the camshaft steps rapidly from position 4 to position 6 to complete the timing of this all red clearance period in position 6, this timing continuing without interruption since despite the momentary closing of the solenoid contact S6 in this rapid stepping action the discharge circuit for condenser KA is via contact S6 is interrupted by the open break contact BYR160 as previously described, the timing of the all red clearance period being continued in position 6 by reason of the fact that relay GYR is maintained locked up energized over its contact BYR6 and cam contact C8A, wire 148 and make contact BYR14 to negative power, thus holding relay GYR energized during the rapid stepping through position to position 6, the relay GYR remaining energized in position 6 over cam contact C11A.

Reviewing briefly the operation of the apparatus or control system according to the invention the normal resting condition in the absence of traffic is with the signals all red for the intersecting roads. From this condition upon actuation by an approaching vehicle on either one of the roads alone the sub-cycle of the signals will be initiated including a brief all red delay period to control the speed of such vehicle, followed by a green period for such road alone, followed by a yellow period for such road alone and followed by return to an all red signal display, with the apparatus returning to rest again with this signal display continuing in the absence of further tratfic actuation. Throughout this sub-cycle the signal remains red on the other intersecting road. It will be appreciated that in the preferred form of the invention illustrated the first part of the all red signal display upon return thereto is timed separately in the controller to provide an all red clearance period following the yellow period, insuring substantially a minimum all red period of whatever length desired by adjustment of this timing by the appropriate adjusting resistor A2C or B2C as the case may be. However since there is no change in the signal display during this all red condition from the all red clearance period to the all red rest period, there is no difference in the signal display apparent to approaching trafiic, and where it is desired to keep the all red display prior to the red delay period at a minimum value, thus to minimize or substantially eliminate any overlapping or all red period in the shift of right of way from one road to waiting traflic in the other road, the adjusting resistors A2C and B2C can be set to a minimum value such that the timing of this part of the all red signal display will be only a fraction of a second for example, and thus be negligible so that efiectively from the viewpoint of waiting trafiic the green signal will appear to follow substantially immediately after the end of the yellow signal on the opposite road.

Continuing with the brief review of operation of the controller it will be noted that the red delay period is efiectively eliminated in the transfer of right of way from either road to waiting traffic on the other road, the controller stepping rapidly through the all red rest and red delay positions, but timing in each such case the all red secondary clearance period following the yellow period for the road losing the right of way. However as pointed out above these red clearance periods may be reduced to a substantially negligible value to in efiect substantially eliminate them if desired.

It will be appreciated that when the right of way is transferred from one road in response to waiting trafiic on the other road, the elimination of the red delay period as automatically provided is desirable since this waiting trafiic is stopped or substantially so and there is no need for the red delay as a speed controlling factor for such waiting trafiic.

It will be further noted however that in each return from green to red for either road under the various traffic conditions described, a yellow signal period will be interposed only on the road so losing the right of way while the red signal remains on the opposite road. Therefore in accordance with the invention, all approaching or waiting trafiic whether isolated vehicles or closely spaced or grouped vehicles will observe the usual uniform cycle of signal colors in the accord and removal of right or way to its road, and that each accord of right of way includes a green signal period variable between a minimum length for a single vehicle to an indefinitely extendable length for trafiic on either road in the absence of any traffic on the opposite road, but up to a maximum length in case of any traflic waiting on the opposite road.

It will be appreciated by those skilled in the art that the coils of relays AS and CS may be sleeved or otherwise arranged for slow release if desired to assure substantially full discharge of condenser KA or to increase the time of operation of solenoid S. It will similarly be appreciated that other forms of step by step cyclic switching mechanism may be employed for operating the several contacts of the C-series illustrated and referred to in the preferred embodiment as cam contacts.

It will also be similarly understood that other forms or arrangements of electronic timing circuits may be used within the scope of the invention as limited by the claims.

In the present apparatus as illustrated for example in the preferred embodiment a two electrode gas discharge tube designed to become conducting at about 63 of the charging voltage is employed, with the charging circuit employing values of control resistance and values of capacitance for condenser KA and KB for example such that the product of these two values for the charging circuit is equal to the timing desired in seconds, where the resistance is in megohms and the capacitance in microfarads, although this relationship is given in an illustrative sense rather than in a limiting sense.

It will be understood by those skilled in the art that various other modifications in the structural details, or the arrangement of the parts, or changes in the design herein exemplified may be made without departing from the spirit of the invention within the scope of the claims.

I c aim:

1. A trafiic control system for intersecting roads having stop, go and caution signals for each of the roads, trafiic detectors for actuation by traflic approaching in the respective roads, and a controller for operating the signals to accord right of Way alternatively to the roads between minimum and longer time periods in response to actuation of the respective detectors and to interrupt right of way by operation of the stop signals only in the roads in absence of such actuation, said controller including a time controlled step-by-stcp cyclic switching unit having a cycle of positions through which it is adapted to be operated in response to detector actuation and including a position for operating the go signal for one of the roads and the stop signal for the other road, a following position for operating the caution signal for said one road and the stop signal for said other road, another position for operating the go signal for said other road and the stop signal for said one road, a following position for operating the caution signal for said other road and the stop signal for said one road, a further position for operation of the stop signals in bothof said roads with said switching unit at rest in the absence of actuation of either of said detectors, timing means for operating said switching unit from said rest position in response to actuation of the detector in either one alone of said roads and through a sub-cycle of such positions to provide in succession a preliminary period of continued operation of said stop signals for both of said intersecting roads to delay accord of right of way to trafiic which may be approaching at excessive speed, followed by a period of operation in such go signal position for said one road, followed by a period of operation in such caution signal position for said one road, followed by restoration of operation of the stop signals alone and return to said normal rest condition to complete said sub-cycle in absence of further actuation but prepared for a repetition of such sub-cycle of operation for the same road in response to a further actuation in said same road alone and for a corresponding sub-cycle of operation for the said other road in response to a further actuation in said other road alone 2. A traffic control system as in claim 1, and said controller including means operated in response to actuation of a detector on either one road alone to operate said controller rapidly through the positions for the said preliminary stop signal period and following go signal period and following caution signal period for said other road, all while maintaining the stop signal alone operated in said other road during such sub-cycle for said one road and return to said normal rest position.

3. A traffic control system as in claim 1, and said controller including means operated in response to actuation of a detector on either one road during accord of right of way to the other road to continue said cycle switching unit through the cycle to accord right of way to said one road with a go signal period, a following caution signal period and return to all stop signal operation but to omit effectively said preliminary stop signal delay period before said latter accord of right of way.

4. A trafiic control system as in claim 1 and including means for dividing said go signal period for either one road into a predetermined non-extendable initial interval followed by a vehicle interval extendable by such traffic actuation on said one road during such vehicle interval to provide a longer minimum go signal period in response to a single original actuation than the amount of prolongation of such go signal period in response to such a single extending actuation.

5. A traffic control system for intersecting roads having stop, go and caution signals for each of the roads, trafiic detectors for actuation by traffic approaching in the respective roads, and a controller for operating the signals to accord right of way alternatively to the roads between minimum and longer time periods in response to actuation of the respective detectors and to interrupt right of way by operation of the stop signals only in the roads in absence of such actuation, said controller including a time controlled step-by-step cyclic switching unit having a cycle of positions through which it is adapted to be operated in response to detector actuation and including a position for operating the go signal for one of the roads and the stop signal for the other road, a following position for operating the caution signal for said one road and the stop signal for said other road, another position for operating the go signal for said other road and the stop signal for said one road, a following position for operating the caution signal for said other road and the stop signal for said one road, a further position for operation of the stop signals in both of said roads with said switching unit at rest in the absence of actuation of either of said detectors, timing means for operating said switching unit from said rest position in response to actuation of the detector in either one alone of said roads and through a sub-cycle of such positions to provide in succession a preliminary period of continued operation of said stop signals for both of said intersecting roads to delay accord of right of way to traffic which may be approaching at excessive speed, followed by a period of operation in such go signal position for said one road, followed by a period of operation in such caution signal position for said one road, followed by restoration of operation of the stop signals alone and return to said normal rest condition to complete said sub-cycle in absence of further actuation but prepared for a repetition of such sub-cycle of operation for the same road in response to a further actuation in said same road alone and for a corresponding sub-cycle of operation for the said other road in response to a further actuation in said other road alone, and said controller including means operating in the caution signal positions for the respective roads to interrupt the caution signal operation at the end of its period and to substitute opera tion of the stop signal for the same road along with that of the other road for an all-stop time period before operation of the cyclic switch unit to its following position of normal all-stop signal operation in which it rests in the absence of actuation, and means for effectively omitting the stop signal delay period in continuing through such all-stop signal condition to complete a full cycle in response to actuation on said other road before the end of the sub-cycle on said one road.

6. A trafiic control system for intersecting roads having stop, go and caution signals for each of the roads. traific detectors for actuation by trafiic approaching in the respective roads, and a controller for operating the signals to accord right of way alternatively to the roads between minimum and longer time periods in response to actuation of the respective detectors and to interrupt right of way by operation of the stop signals only in the roads in absence of such actuation, said controller including a time controlled step-by-step cyclic switching unit having a cycle of positions through which it is adapted to be operated in response to detector actuation and including a position for operating the go signal for one of the roads and the stop signal for the other road, a following position for operating the caution signal for said one road and the stop signal for said other road, an other position for operating the go signal for said other road and the stop signal for said one road, a following position for operating the caution signal for said other road and the stop signal for said one road, a further position for operation of the stop signals in both of said roads with said switching unit at rest in the absence of actuation of either of said detectors, timing means for operating said switching unit from said rest position in response to actuation of the detector in either one alone of said roads and through a sub-cycle of such positions to provide in succession a preliminary period of continued operation of said stop signals for both of said intersecting roads to delay accord of right of Way to traific which may be approaching at excessive speed, followed by a period of operation in such go signal position for said one road, followed by a period of operation in such caution signal position for said one road, followed by restoration of operation of the stop signals alone and return to said normal rest condition to complete said sub-cycle in absence of further actuation but prepared for a repetition of such sub-cycle of operation for the same road in response to a. further actuation in said same road alone and For a corresponding sub-cycle of operation for the said other road in response to a further actuation in said other road alone, and said controller including means operating in the caution signal positions for the respective roads to interrupt the caution signal operation at the end of its period and to substitute operation of the stop signal for the same road along with that of the other road for an all-stop time period before operation of the cyclic switch unit to its following position.

7. A traffic control system as in claim 1, and said timing means including means for individual adjustment of timing for the said preliminary periods of continued operation of said stop signals for both of said intersecting roads to delay accord of right-of-way for times individual to the respective roads.

8. A trafiic control system as in claim 1, and said timing means including means for individual adjustment of timing for the several respective time periods in each said sub-cycle for the respective roads.

9. A traflic control system for intersecting roads having stop, go and caution signals for each of the roads, traffic detectors for actuation by traffic approaching in the respective roads, and a controller for operating the signals to accord right of way alternatively to the roads between minimum and longer time periods in response to actuation of the respective detectors and to interrupt right of way by operation of the stop signals only in the roads in absence of such actuation, said controller including a time controlled step-by-step cyclic switching unit having a cycle of positions through which it is adapted to be operated in response to detector actuation and including a position for operating the go signal for one of the roads and the stop signal for the other road, a following position for operating the caution signal for said one road and the stop signal for said other road, another position for operating the go signal for said other road and the stop signal for said one road, a following position for operating the caution signal for said other road and the stop signal for said one road, a further position for operation of the stop signals in both of said roads with said switching unit at rest in the absence of actuation of either of said detectors, timing means for operating said switching unit from said rest position in response to actuation of the detector in either one alone of said roads and through a sub-cycle of such positions to provide in succession a preliminary period of continued operation of said stop signals for both of said intersecting roads to delay accord of right of way to traffic which may be approaching at excessive speed, followed by a period of operation in such go signal position for said one road,

followed by a period of operation in such caution signal position for said one road, followed by restoration of operation of the stop signals alone and return to said normal rest condition to complete said sub-cycle in absence of further actuation but prepared for a repetition of such sub-cycle of operation for the same road in response to a further actuation in said same road alone and for a corresponding sub-cycle of operation for the said other road in response to a further actuation in said other road alone, and said cyclic switching unit including a separate position for said preliminary all-stop signal delay period immediately following said normal all-stop signal position and said timing means including adjustable time controlled relay means for providing the respective all-stop time delay periods for the respective roads in said separate position of said cyclic switching unit in response to actuation in the respective roads.

References Cited in the file of this patent UNITED STATES PATENTS 2,126,695 Wright Aug. 9, 1938 2,249,100 Wilcox July 15, 1941 2,297,683 Barker Oct. 6, 1942

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