US2288601A - Traffic cycle selector apparatus - Google Patents

Description

y 7, 1942- J. L. BARQKER 2,288,601

TRAFFIC CYCLE SELECTOR APPARATUS Filed Aug. ie, 1940 2 Sheets-Sheet 1 Craze 5ELEC7'0E CZQMMWYCZ ATTORNEY Patented July 7, 1942 TRAFFIC CYCLE SELECTOR APPARATUS John L. Barker, Norwalk, Conn, assignor to Automatic Signal Corporation, East Norwalk, Conn, a corporation of Delaware Applicaticn August 2, 1940, Serial No. 349,597

g 20 Claims.

This application relates to traific signal control apparatus and especially to cycle selecting apparatus for use in conjunction with a master controller or master timer which governs a number of local or individual intersection traffic signal controllers for control of traflic right of way at individual intersections. The master controller may also serve directly or indirectly as a traiiic signal controller for one intersection.

The cycle selecting apparatus is arranged to periodically effect a choice from a number of available master timer operating cycles of one cycle whose length or control features shall be best suited in accordance with the general level of traffic density for most effective dispatch of such traffic thru the area served by the master timer.

In addition the cycle selector embodies apparatus to select and render effective various ones of a number of available different plans of operation for the master controller. For example the individual local controllers at several intersections of cross roads along a main road may be co-ordinated by the master controller in accordance with a progressive trafiic control system in which accord of right of Way to the main road is made progressively by the several local signal controllers, or may be coordinated with a synchronized system in which accord of right of way at the several intersections is substantiallysimultaneous, or the local controllers may be freed from co-ordination, all depending on which cycle of the master controller is being rendered effective by the cycle selecting apparatus.

The individual intersection controllers may be t of the full or semi-trafficactuated type in which the transfer ofright of way to one road from another to initiate a right of way signal cycle is made responsive to tramc actuation of a traflic detector in such one road, or may be of the fixed time (non-traffic actuated) type, or some may be" of one and others of another type, or they may be changed over from one type to another under various conditions.

Accordingly it is an object of the invention to 1 provide cycle selecting apparatus for use in con-.

junction with a master traffic signal timer having a number of different operating. cycles to effect periodically a selection of such available cycles in accordance with the traffic density level as determined by the number of trailic detector actuations over a cyclically repeated counting period.

Another object is to provide a cycle selector of this type which while causing operation of the master timer on one cycle length will in the event of failure of traflic to reach a predetermined count to hold such cycle length within a preset cyclic counting period, cause operation of the master timer on the next shorter cycle in the next counting period, and in the event traffic attains such predetermined count in a preset fractional part of the total cyclic counting period, will cause operation on the next longer cycle in the succeeding counting period.

A further object is the provision of cycle selecting apparatus for use in conjunction with a master traffic signal controller having a number of operating cycles of different time lengths, to count traific during a time period While th master controller is operating on one selected cycle and to select the next longer cycle or next shorter cycle or the same cycle respectively for the next counting period in accordance with whether the traffic count is materially greater or less or substantially equal to respectively a predetermined amount to which such time cycle is suited.

Another object is to provide traflic signal cycle selecting apparatus for control of a master controller for a series of individual intersection traffic signal controllers along a road and having a number of different traffic signal cycles including one minimum cycle providing independent control of the individual controllers responsive only to traffic actuation of a trafiic detector at the individual intersections, a number of other cycles of successively longer time length providing coordinated control of the several individual controllers to have accord of right of way proceed progressively along the road at successively lower traiiic speeds, and acycle of maximum length 7 providing synchronized coordinated control of the individual controllers for substantially simultaneous accord of right of Way, the cycle selector counting traflic actuations over a time period while providing one selected intermediate cycle for example, and shifting to the next longer cycle or the next shorter cycle or retaining the same cycle in accordance with counting more or less trafiic or substantially the same traflic respectively as a predetermined amount of traffic to which the cycle is suited.-

stepping switch to a new position to obtain the next shorter cycle length in the event that the shortening of cycle is desirable for example.

Still another object provides that the present cycle selector equipment in addition to determining master timer cycle length is effective also in determining in accordance with the level of traffic density whether individual local intersection controllers shall operate under one or another of various co-ordination plans under the master timer or shall operate free and independently of the master timer. 7

Another object provides that the cycle selecting equipment cause a unit shortening change in master timer cycle length if the traffic falls below a predetermined required trafiic level in a single counting period or cause a unit lengthening change in cycle length if the traffic attains the predetermined level in a preselected fractional portion of the counting period, or cause the cycle length to remain unchanged if the traflic fails to reach the predetermined level in the preselected fractional time but does so attain the predetermined level within the full counting period.

In a number of instances where a plurality of individual intersection trailic signal controllers are located at related intersections along a main road continuous movement of platoons of trafiic ,is facilitated by rendering the cycles of operation of the local controllers subject to the governing influence ofa master timer which determines when each local controller may start its cycle of operation. Local controllers of both full and semi-actuated'type as well as fixed-time cycle controllers have been co-ordinated. under a mastertimer.

It has long .been appreciated by trafiic authorities that the widely varying conditions of trafiic flow .or distribution during a 24 hour period cause considerable maladjustment and loss of efliciency in many trafiic signal systems in which the same coordination pattern or master timer cycle is'imposed continuously on the local controllers and-some automatic selection among several different cycles would 'be desirable. For example for ordinary traffic densities a progressive coordination system in which the several local controllers are each permitted to transfer right of way from the main road at progressively staggered intervals in the master timer cycle may be found most satisfactory for trafiic movement, while in periods of very heavy traflic concentration a synchronized coordinated system wherein all local controllers simultaneously make transfers of right of way from the main road may be desirable toprovide a sufi'iciently long cycle to care for the heavy trafiic without excessive reduction of traffic speed. In some instances of very heavy traffic it is desirable to insert an exclusive pedestrian period in the cycle but such an addition to the cycle may make the cycle too long for proper progressive operation so that a change to synchronized operation may be necessary.

Further, in periods of very light trafilc the individual controllers cause least delay to traflic if each is free of coordination and arranged to operate as an. independent traffic actuated controller. Additionally it has been demonstrated that when operated as a progressive coordinated system greatest facility of traffic movement is obtained by utilizing master timer cycles of increased length as the density of traflic increases and its speed. decreases, since the proper cycle length for progressive systems is inversely proportional to the speed of traflic through the system.

The present invention provides cycle selector equipment responsive to traflic actuation for use in conjunction with a master timer in a system of this character and in which the local controllers will be operated on a master timer cycle of suitable length and character depending upon the density level of trafiic, the local controllers being freed from coordination on the shortest cycle, being coordinated on a synchronized plan on the longest cycle, and being coordinated on a progressive plan on intermediate length cycles.

For the purposes of this application the master controller or timer controlled by the cycle selector may be considered to be for example a circuit controller driven through gearing by an induction disc type motor at any one of a number of different speeds by one of a number of suitable driving coils depending upon which one of the coils in energized. From suitable cam controlled contacts, operated by such motor, circuits are closed to each of the individual intersection controllers for governing their operation.

A local controller may for example be of the type which normally rests in a position where right of way is accorded to the main road, but upon actuation of an associated cross road trafiic actuatable device the controller operates through a cycle in which right of way is transferred to the cross road and subsequently retransferred to the main road. When operated as part of a co-' ordinated system the initiation of the operating cycle responsive to actuation is made dependent upon the brief interruption or cessation of a preventive control connection from the master timer, the interruption of this preventive impulse at a predetermined point in the master timer cycle being the signal for permitting transfers of right of way from the main road by the local controller in response to actuation. Many other suitable types of master timers or local controllers are well-known in the art and readily adapt themselves for substitution for the ones mentioned for purpose of example. For instance instead of transmitting to the local controllers a continuous preventive impulse which is interrupted once in each cycle to allow each local controller to transfer right of way from the main road, the master timer may be arranged to send out "permissive impulses of short duration. at the desired cyclic intervals. In this case the terminal equipment in the local controllers would be arranged to complete operating circuits upon receipt of such impulses rather than upon cessation of the proventive impulse.

Examples of systems illustrating local traflic actuated signal controllers subject to preventive impulses from a master timer aredisclosed in Patent 2,241,047 issued May 6, 1941 to H. A. Wilcox. Examples of systems. having local traflic actuated signal controllers subject to periodic permissive impulses from a master timer are disclosed in Patent 2,110,723, issued March 8, 1938, to C, D. Geer and J. L. Biach; Patent 2,122,411, issued July 5, 1938, to E. H. Eames; and also in Patent 2,105,443, issued January 11, 1938, to A. P. B. Renshaw, the latter patent also disclosing a local cyclic controller of the non-traffic actuated type which is subject, to recycling permissive impulses from the master timer.

The cycle selector according to the invention is arranged to cause operation of the master timer on any one of its available cycles in accordance with the traffic density level which is determined bythe number of actuations of a trafiicactuatable device or devices suitably located for sampling trafiic movement'within a predetermined counting period.

While any one of the several cycles, except the shortest, is in effect a predetermined. appropriate level of traffic is required over a single counting period in order for the selector to retain such cycle for another counting period. The. level required to hold on one cycle is preferably different from that required to hold on another cycle. If at the end of a counting period the predetermined required traffic level has not been reached the selector will place in effect the next shorter master timer cycle. Should, however, the predetermined required traffic level be attained in a fractional part of the counting period, for example the first two-thirds of the period, the selector will render effective the next longer cycle for at least the duration of the next counting period. If it is observed that the cycle in effect is the best cycle for the counted traffic level, the same cycle length will be retained.

The counting period utilized is preferably several times as long as the longest master timer cycle, a six-minute counting period being particularly convenient as it is sufficiently long to average out the relatively large momentary fluctuations in traffic flow often experienced, and to avoid abrupt changes, and to permit four ninety second maximum cycles to occur within the counting period for example. The six minute counting period is sufficiently short, however, to permit the cycle selector to change from the minimum cycle through the four successive traffic intermediate cycles to the maximum cycle in thirty minutes in case the traffic should, in an unusual case, increase as rapidly as this.

Connection is also made by the cycle selector by a special relay group so that when the shortest master timer cycle is being rendered effective, circuit is completed to permit operation of the local controllers as free and independent of coordination by the master timer. When the master timer is made to operate on its longest cycle the cycle selector causes completion of a circuit to switch over to a synchronized plan of coordinated operation in which all of the local controllers are permitted to transfer right of way to their respective cross roads simultane- V ously. On the other available cycles the master timer shown is arranged to govern the local controllers in accordance with a progressive coordinated system, but any desired plan of operation may be set up. Other changes in the form of local controller cycles or in the pattern of coordination, as for instance inclusion under one or more cycle plans of pedestrian periods in the local controller cycles, may be arranged to be effective as. desired as will hereinafter appear.

A description of the cycle selector according to the invention and its manner of. operation will now be presented with reference to the accompanying sheets of drawings in which:

Figures 1 and 2 when placed one over the other form a circuit drawing for an embodiment of the cycle selector together with connections to a form of master timer in conjunction with which the cycle selector may advantageously be employed. Connections to terminal equipment to be provided in each of. several local intersection controllers are also indicated in Figs. 1 and 2. Fig. 3 is a schematic diagram outlining illustrative connections between the cycle selector and master timer and local controllers for three intersections. Figure 1 illustrates the cycle selector proper and Figure 2 shows the connections to an illustrative master controller and associated cycle function change over means. Fig. 3 shows three intersections of cross roads I, II and III respectively with a main road. The traffic signals S at the respective intersections may be of any well known type for controlling the right of way of trafiic under control of the local signal controllers indicated schematically in the drawings- The local signal controller at cross road I is illustrated as of the fixed time or non-traffic actuated type. The controllers at cross roads II and III are illustrated as of the trafiic actuated type connected with traflic detectors ZDI, 2132 and SDI, 3D2 in their associated cross roads, and may be of a number of different forms known in the prior art some of which are represented by the several patents mentioned above for example.

The connections for the detectors and signals are outlined in single line form for simplicity as the details of such connections for detectors Di and D2 are disclosed in Fig. 1, and examples of connections of the signals and of the cross road detectors are disclosed in the prior patents mentioned above.

Leads 94, and 93 are energized by the master timer during the part of its cycle in which it is desired to prevent local controller cycle initiation and are deenergized during the remainder of the master timer cycle in which it is desired to permit local controller cycle initiation. 7

Direct connection of lead 96 from the master timer to the local signal controller at cross road III is illustrated in Fig. 3 and this controller is assumed to be adapted to have its traffic signal control cycle initiated by deenergization of the preventive impulse lead 9%. Connection to the signal controllers at intersections I and II is illustrated by way of terminal relays ICE and ZCR from preventive. impulse leads 94 and 95 respectively to convert to permissive impulse for these latter controllers which are assumed to be of. the type adapted to have their traffic signal control cycle initiated by a permissive. energizing impulse for example.

Relays ICE and 20B are energized by the preventive impulse energization of leads. 94 and 95 respectively and are deenergized between preventive impulses to. close their respective back contactsv lorl and 2.01! to connect one or the other of the power supply leads to provide permissive energization impulses to the respective local controllers at I and II.

The embodiment of the cycle selector in accordance with the. invention disclosed herein is set up to effect a choice from six available cycles. of different lengths obtained through separate driving coils in the master timer. These cycles will be denoted as cycles A, B, C, D, E, and F respectively. Obviously more or fewer cycle lengths or plans of operation for the local controllers may be utilized by constructing the master timer with a different number of driving coils. Connection to the several coils is made by a switch finger or wiper over one bank of a stepby-step multi-pos-ition switch of the iype ordinarily employed in automatic telephony as a line switch. This may be a. sixposition switch or instead may be a standard 25-point stepping switch in which the: six connections to the master timer driving coils are repeated in the same order four times with provision made for advancing the stepping switch quickly through the extra or twenty-fifth contact position.

Operating in conjunction with this stepping switch is a group of three momentary circuitclosing cam operated contacts which are driven for example by a synchronous motor. One of the contact pairs closes near or at the end of each cycle of the synchronous motor to establish a counting period another pair opens momentarily at the end of the cycle and the third pair is arranged in this embodiment to close approximately two-thirds of the way through the counting period. Each actuation of the trafiic-sampling detectors adds an increment of charge to a condenser. If the traffic' level is sufliciently high to cause the charge on the condenser to attain a predetermined value required for discharge through a gas-discharge tube and relay in parallel with the condenser at the twothirds point in the counting period, the stepping switch'is operated to advance its wipers one contact position to set up the next longer master timer cycle (excepting when the longest cycle is already in use). This condition thus efiects an increase in cycle length by the selector in order to facilitate traflic movement at the new higher traflic level.

Should the condenser charge not have attained the predetermined tube discharge value at the two-thirds point in the cyclic counting period no advance of the wipers occurs, and if at the end of the full counting period the condenser charge has still not attained the predetermined value indicating that the traffic density has diminished since the preceding counting period, provision is made to operate the wipers of the stepping switch so that they advance rapidly forward five contact positions, and socome to rest in a position energizing the master timer driving coil for a cycle next shorter than the one effective during the counting period mentioned. If, however, the trafiic density is such that the predetermined value of voltage required for discharge through the discharge tube is not reached by the twothirds point but is so attained before the end of the full counting period then no movement of the stepping switch wipers results and the same master timer cycle is maintained during the entire next counting period.

Provision is made for varying the relative weight or effect of each detector actuation while the cycle selector is rendering any one of the six available cycles efiective so that the required level of traflic to cause an increase in cycle length from the E or next longest cycle to the F or longest cycle for example may be considerably greater (or less) than that required to shift for instance from the A or shortest cycle to the B or next shortest intermediate cycle. These density values may be adjusted independently as desired by manipulating dials provided for this purpose and calibrated in number of cars per hour required to hold on B-cycle, for example, these dials controlling potentiometers which determine the charging voltage and thus the amount of charge in the unit charge condensers and transferred to the cumulative charge condenser at each trafiic actuation.

Referring now to the'figures of drawings which when placed Fig. 1 above Fig. 2 constitute a circuit drawing for the cycle selector apparatus and its connection to one form of master timer. The banks of contacts L| to L5 of the stepping switch are shown aligned along the left-hand side. A five-bank switch having twenty-five contacts on each bank is shown although a switch having a different number of banks might be used, or one with only six contacts per bank for instance.

When bank is provided with a corresponding wiper arm or connecting finger which rotates over contacts I through 25 in turn and then reengages contact I again. All wipers are simultaneously advanced one step or position at a time upon a cycle of energization and de-energization of motor magnet MM. The wipers on each bank are of the bridging type, that is each in moving from one contact to the next engages the latter before it disengages the one from which it is passing, although it is not essential that the wipers on all banks be of this type. Driving magnet MM is operated from rectified current provided by the rectifier RFZ from alternating current 'power leads 5|, 52.

On bank L5 of the stepping switch connection is made for selectively energizing one of the several coils of the master timer driving motor. For example the shortest or A-cycle is obtained when wiper W5 associated with bank L5 is engaging one of contacts 5, H, H, or 24 over which circuit is completed from plus lead 52 via contact sr4, lead 60, wiper W5, lead 6|, coil MA to minus lead 5| for energizing the A-cycle coil. When wiper W5 engages contacts 6, l2, 8 or 25 the B-cycle coil MB is energized, and so on.

Direct current for charging condenser KC by units of trafiic is furnished from rectifier tube RFI suitably connected to the secondary of transformer TF. Filter condenser KF serves to provide a steady current on the D. C. output. Lead 5| is the common grounded side of both the A. C. and D. C., lead 52 the ungrounded side of the A. C. source and lead 53 the ungrounded side of the D. C. circuit, the lead 53 also being identified with a plus in a square.

The counting period is established by a plurality of cyclically operated contact pairs shown herein as cam-operated contacts rl, sl, tl operated respectively by cams R, S, and T on shaft 15 rotated by gearing or otherwise by a synchronous type motor 54 which is continuously driven at constant speed by a circuit from plus lead 52 via leads 55, 56, to minus lead 5|. The shaft 15 and cams are arranged to make one revolution every six minutes to constitute the counting period previously mentioned.

The traffic-sampling detectors DI, D2, shown as pairs of contacts for illustration, may be located in any desired location in one or more of the roadways involved in the trafiic signalling system and any desired number of detectors may be employed to obtain a representative trafiic count.

The manner of counting detector actuations will now be described. Connected in parallel the detectors are arranged so that trafiic actuation of any one of them Will momentarily energize relay DR via leads 51, 58 to minus lead 5|. In the de-energized position of relay DR circuits are completed over contacts drl through dr5 respectively to charge unit condenser Kl through K6 one of which is associated with each of the six available different cycles; condenser Kl being associated with the A-cycle, K2 with the B-cycle and so on.

In the present embodiment separate unit condensers are employed for each cycle in order that diiferent values of trafiic level required to hold a cycle may be assigned for each cycle. Thus when any one cycle is in operation the efiect of a single detector actuation toward retaining such cycle in operation, or changing the cycle, is independent of the other cycles.

Potential is applied to these unit condensers, in the back contact or non-actuated position of relay DR, from one of potentiometers RA, RB or RC. For example a voltage is applied to unit condenser K3 from potentiometer RB via lead 69, back contact dr3, lead 10 condenser K3. Assuming for the moment that the wipers of the stepping switch are standing in position 1 (or 7, 13 or 19), rendering C-cycle effective, any actuation of detector DI causes energization momentarily of relay DR, the unit charge on condenser K3 is substantially transferred to condenser KC since at contact dr8 circuit is now completed from condenser K3 via contact I on bank L3, wiper W3, lead H, contact dr3, lead 59, contact g3 to condenser KC, connecting condenser K3 and KC in parallel, to minus lead The voltage across these condensers must now be the same and the charge on K3 will be divided between them in proportion to their respective capacities. Accordingly since KC is relatively very large compared to K3 the charge on K3 is substantially transferred to condenser KC.

Subsequent de-energization of relay DR breaks the connection between these condensers at 118, and at dr3 a circuit is completed to place a new unit charge on condenser K3 from potentiometer RB. Successive traific actuations in a similar manner within the same counting period increase the charge on condenser KC in steps. Although each additional unit of charge transferred to condenser KC is not so large as the first such unit, the same number of transfers from a certain one of the unit condensers in a counting period will always result in the same potential on condenser KC. That is, 20 actuations of the detectors causing 20 operations of relay DR. for instance will always result in a certain corresponding voltage having been acquired by KC and conversely for any given voltage on KC a corresponding constant number of actuations must have occurred to produce it.

The relative size of the unit charges, or relative weight per detector actuation, when A-cycle is eiiective (stepping switch positions 5, 11, 1'7, 24) may be adjusted at potentiometer RA; the effect of each actuation is increased by moving the potentiometer pointer toward the lefthand end of the potentiometer and. decreased by moving it toward the right-hand end. When cycles B, C, D or E are in effect, the relative weight per actuation is controlled by potentiometer RB, and during cycle F operation by potentiometer RC. Accordingly independent adjustment of the relative weight per actuation toward maintaining a particular cycle in effect or toward changing it may be made at will at these potentiometers which are conveniently dial controlled, and are calibrated in number of actuations per counting period required to hold cycle.

Since the average number of axles or actuations per vehicle is two, and the 6 minute counting period is T of an hour, the number of vehicles counted per hour is five times the number of actuations per counting period so that if desired this calibration may be converted to traffic density in vehicles per hour required to hold cycle.

Obviously if still different values of Weight are desired for each of the intermediate cycles instead of. the single potentiometer RB shown additional potentiometers may be provided connected separately to contacts dr2, M3, 1114, and dr5. A single potentiometer'might be utilized in which case contacts drl anddrfi would also be connected to potentiometer RB with RA-andRC eliminated. Setting of the general range oftraffic density required to hold the cycle for each cycle is made by provision of the proper sized unit condenser for each cycle, and finer adjustments within this general range are made by the potentiometer dials to suit the traflic range and number of counting detectors at each particular signal system installation to which the cycle selector may be applied.

Operation of the cycle selector in changing or maintaining a cycle will now be described. Assuming again the C-cycle to be in operation and the stepping switch wipers to be in position 1, three conditions of operation will now be considered. First, if the predetermined required trafiic level or density tohold on C-cycle shall have been registered by the two-thirds point in the counting period the neXt longer cycle or D- cycle is rendered effective during the succeeding counting period; second, if the predetermined level of traffic has not been registered before the end of the counting period, the nextshorter or B-cycle will be placed in effect during the next counting period; third, if the predetermined reg" istered level is not registered at the two-thirds point but is so registered by the end of the counting period the C-cycle is maintained over the succeeding counting period. These conditions will now be considered in more detail.

Condition 1.--Assume sufiicient actuations have occurred to increase the charge on condenser KC in the manner described so that before the two-thirds point of the counting period is reached the potential across condenser KC attainsthe flash potential of tube FC. As soon as such a potential exists across tube FC the tube suddenly becomes conducting and momentarily energizes relay CS in series with the tube. At contact csl, circuit is completed via leads l2, T3 to energize auxiliary. relay V which looks in over contact 04, lead 1.4, cam contacts 1 to minus lead 5l.

As camshaft l5 completes two-thirds of a revolution from the start of the counting period, as indicated inthe accompanying cam chart, cam S closes contactssl and negative power is applied to rectifier RFZ to energize stepping magnet MM via lead 16, contact 01, lead "ll, contact on bank Ll wiper WI, lead 18. Magnet MM is then deenergized as cam S opencontacts slalmost immediately. The cycle of energization and de-energization of magnet MM causes the Wipers to be advanced one position to position 2 in which the next longer or D cycle is effective for at least the duration of the next counting period.

It will be observed from the cam chart diagram that cam contacts 1| are closed by cam R just prior to the end of the cycle for a short period. Via cam contacts Tl leads i9, 80, relay G is energized during this closure. of contacts TI, and during the pull-in and drop-out of this relay, circuit is closed momentarily at contact 94 to short-circuit the condenser KC thru a low resistance RP to reduce the charge on the condenser substantially to its zero 'or starting potential for charging in the ensuing counting period.

At the end of the counting period, cam contacts tl open, breaking the holding circuit for relay V' which is de-energized and the counting apparatus returned to starting condition for another counting period. t. r

Advancing of the stepping switch from position 2 to 3 in the next counting period so as to make E cycle effective similarly results if the voltage across condenser KC has been raised before the two-thirds point of the counting period to the flash potential of tube FC by sufficient traffic actuations while operating on D-cycle. The unit charge condenser in use on D-cycle is smaller than that used on C-cycle so that more traflic actuations will be required to step up from D to E than from C to D. When the longest or F-cycle is in operation, flashing of tube PC at the twothirds point in the counting period does not advance the stepping switch since F is the maximum cycle and the next position of the stepping switch provides the A-cycle, and therefore contacts 4, I0, I6, 22 which correspond to the F-cycle are open at bank Ll, to interrupt the step-up circuit, and in this event the F-cycle would be maintained for another counting period.

Condition 2.Assume the predetermined required level of traffic necessary to hold a cycle has not been registered before the end of the counting period. Under this condition at the two-thirds point in the counting period when contacts sl are closed and shortly afterward reopened the charge on condenser KC will not have been sufiiciently augmented by trafiic actuations to exceed the flash potential of tube FC. The consequent sequence of operations described above resulting in the one-step advance of the stepping switch does not occur, since relay V is not locked-in while contact sl is closed.

As indicated in the cam chart immediately prior to the end of the cycle contacts rl are closed by cam R energizing relay G via leads 19, 80. This relay when operated ends the counting period by resetting the condenser KC to its starting potential at make-break contact g4, interrupts the charging of condenser KC from unit condensers KIK6 at contact 93, and at contact gl prepares a circuit for testing whether the selector will remain in the same position for operating the master timer on the same cycle for another counting period or whether in the event that the trafiic level required to hold on the same cycle has not been attained the cycle selector will prepare to select the next shorter master timer cycle as the next counting period.

Since it is assumed that the trafiic has been insufficient to raise condenser KC to the tube FC flash potential, which represents the traffic level required to hold the cycle, the tube FC will not have discharged and relays CS and V will not have been energized. The contact will thereupon complete circuit from plus lead 53, via lead 8|, coil of relay SC, contact gl, lead 82, contact 1 3, resistor RSC, contact mrl, to lead energizing relay SC. A sequence of relay operations then ensues to advance the stepping switch wipers ahead five positions so that if as previously assumed the wipers were standing in position 1 (cycle C), they will be rapidly advanced to position 6 (cycle B).

When relay SC is energized it completes circuit from minus lead 5! via its contact 802, contacts v2, srl, leads 83, 18 to energize rectifier RF2 and motor magnet MM. The latter magnet at contact MMI energizes relay SR, which in turn interrupts the motor magnet energizing circuit at srl. Energization and de-energization of magnet MM advances the wipers one position forward.

Meanwhile, relay SR prior to its energization, completed a circuit from D. C. plus lead 53 over contact sr3, lead 84, resistance RG to apply a charge on condenser KG. When relay SR is operated by magnet MM, condenser KG is connected in parallel with condenser KC at contact s12 via contact on bank L2, wiper W2, lead 85, contact 92, condenser KC. Condenser KC being relatively larger in capacity than KG, the charge from the latter is substantially transferred to condenser KC. De-energization of magnet MM by the opening of back contact srl causes relay SR to drop out again and at sr3 a new charge is applied to condenser KG.

As soon as relay SR drops out, however, the sequence is repeated: MM energizes, SR energizes, more charge is added to condenser KC, magnet MM drops out advancing the wipers to position 3 and relay SR drops out. The size of condenser KG is so selected that after the fifth operation of relay SR, upon the fifth stepping of wipers forward, condenser KC will have acquired a potential in excess of tube FC flash potential, tube FC discharges operating relay CS and energizing relay V which locks-in over contact 114. At 123 the energizing circuit for relay SC is broken, and at contact 02 the automatic stepping circuit for magnet MM is interrupted, the wipers, therefore, come to rest five steps from their starting position, in position six where on bank L5 connection is established for energizing coil MB to provide B-cycle operation, the next shorter cycle for the next counting period. The closed contact portion of cam R is sufficiently long for the automatic 5-step operation of the wipers and when camshaft 15 rotates into the final portion of its cycle where cam contacts rl open relay G is de-energized causing condenser KC again to be reset at contact g4. When cam contacts ti open, relay V is de-energized and all relays are in de-energized position to commence the next counting time period.

If the selector is causing operation on the A or shortest cycle the circuits described are ineffective to cause 5-step advance of the wipers even should traific fail to attain the appropriate required level to hold cycle, and the selector continues to select A-cycle operation for another period. Since on bank L4 the A cycle positions (5, 11, 1'7, 24) are connected to cause energization of relay MR via a circuit from lead 52, coil of relay MR, lead 86, contacts of bank L4, wiper W4, leads B1, 88 contact scl to minus lead 5!, relay MR is energized and at opened contact mrl, energization of relay SC which is essential for starting the 5-step sequence, is prevented.

When the 5-step stepping sequence includes contact 23 as one of the 5 steps passed through, it is necessary that this contact position, which is arranged to be the extra or odd contact when four groups of six diiferent cycle connections are usedon a 25-point standard stepping switch, be passed over without being counted as one of the 5 steps. Accordingly position 23 is not connected on bank L2, and no charge from condenser KG is added to condenser KC in this position upon operation of relay SR and contact srZ. The stepping of the wipers by magnet MM and relay SR into position 23 is therefore not counted by condenser KC as one of the 5 steps in the automatic stepping sequence, and the wipers never come to rest in this position. Due to the fact that bridging type wipers are shown employed on bank L2, position 22 is also left unconnected in order that there will be no possibility of the 23rd contact position being counted, the transfer of charge at contact sr2 for :00-

sition 22 occurring before the bridging type wiper has cleared contact 2|.

Opening of the contact s1'4 in the energized periods of relay SR during the stepping operation opens the power circuit to the master timer driving coils to prevent momentary energization of more than one of the driving coils at a time, which energization might alter unnecessarily the speed of the induction disc in the following mas" ter timer cycle.

Condition 3.Assume the predetermined traffic level is not registered before the two-thirds point in the counting period but is so registered before the end of the counting period. Under this condition when contacts s| are closed and shortly thereafter re-open approximately at the twothirds point in the counting period the charge on condenser KC will not have been sufficiently augmented from its initial value of substantially zero by traffic actuations to reach its final value at the flash potential of tube FC. The consequent sequential operations resulting in the single stepping of the stepping switch do not occur, since relay V is not then looked-in.

When contacts Tl are closed at the end of the counting period it is here assumed that sufficient traffic actuations have occurred, after cam contact sl closed and opened, to have permitted tube FC to flash, operating relay CS, and locking-in relay V. The closure of contacts TI and resulting energization of relay G will not initiate the 5- step stepping sequence for lowering the cycle length since contact '03 is open. No operation of the motor magnet MM results therefore, the breaking of contacts Tl de-energizes relay G which at contact g4 resets condenser KC for traffic counting in the next period. Subsequently contacts tl open, de-energizing relay V, and the selector is prepared to start the next counting period, with the stepping switch remaining unchanged in position and the same master timer driving coil MC energized for C-cycle.

While the cycle selector is causing operation on the intermediate master timer cycles, as cycles B, C, D and E, it is generally desirable that the several local individual intersection controllers be coordinated in accordance with a progressive plan in which the times in the master cycle at which the several local controllers are permitted to transfer right of way from the main road in response to cross road actuation differ from one another in accordance with the preset plan for progressive accord of right of way along the main road at the several local controllers.

The preventive impulse to the local controllers normally operates terminal equipment in each controller which is de-energized in a portion of the master timer cycle by interrupting the preventive impulse for a brief period to permit initiation of the local controller cycle. Three such preventive impulse circuits to local controllers are shown herein for example, although more or les such circuits may be used as desired, depending on the number of local controllers in the coordinated system, power normally being extended from plus lead 52 via switch SQ, lead 90, contact ql, leads 9|, 92, contact p2, lead 93, thence to the respective local controllers via master timer contacts, as for example to local controller #1 via cam contacts tal and lead 94. The opening of cam contacts tal, tb l, tcl in order establishes a progressive coordinatedoperating plan for the local controllers. Adjustment of the open contact periods of cams TA, TB, TC permit any desired progressive plan for local controller operation to be set up. Parallel circuits via contacts of relay Z are continuously open under progressive plan operation since relay Z i maintained energized via circuit from plus lead 52 relay Z, contact pl, lead 91, lead 5|.

Arrangement is provided to release the several local controllers from the coordination plan when the cycle selector is causing operation on the shortest or A cycle of the master timer, so that each local controller transfers right of way from the main road in response to cross road traffic actuation independently of the master timer. While the A-cycle is in operation, therefore, that is, while the stepping switch wipers are in positions 5, 11, 17, or 24, relay Q is energized by circuit from minus lead 5|, contact s01, leads 88, 89, contact 'mrZ (relay MB is energized in these positions of the stepping switch), relay Q, lead 99, switch SQ to plus lead 52. At open contact q| power from plus lead 52 is broken to all the master timer contacts and to the outgoing preventive impulse circuits to the local controllers so that each is rendered free from master timer coordinated control.

Under very long master timer cycles it has generally been found desirable in the handling of large traffic volumes to utilize a synchronized coordination plan, under which the preventive impulse circuits to all the local controllers are interrupted at the same point in the master timer cycle. On the longest or F-cycle, (stepping switch position 4, 10, 16, 22) relay P is energized from minus lead 5|, contact sol, leads 88, 81, wiper W4, contacts on bank L4, leads 93, 99, relay P, lead I99, switch SP, to plus lead 52. At

open contact 1132 power to the master timer contacts tal, tbl, tcl is broken and at contact pl the energizing circuit for relay Z is broken. A circuit shunting the master timer contacts tal, tbl, tc| is now completed once in each master timer cycle by contacts mts| from plus lead 52, switch SQ, lead 99, contact ql, leads 9|, liH, contact mtsl, lead 93 and thence over back contacts ZI, Z2, Z3, and leads 94, 95, 96 respectively to the several local controllers so that the preventive impulse circuits to all are simultaneously made and broken at contact mtsl. If synchronized operation is desired on the E or next longest cycle as well as on the F cycle switch SE is closed to energize relay P in the E-cycle positions of the stepping switch.

Opening of switch SQ interrupts the power to all preventive impulse circuits and is accordingly opened when it is desired to free all local controllers from coordination regardless of the master timer cycle length currently in effect.

When switch SQ is closed and switch SP is open, the synchronized coordination plan is eliminated, and the progressive plan efiective on cycles F and E as well as on cycles B, C, and D. Obviously other relay and switch arrangements and combinations may be provided to produce synchronized, progressive or independent operation on cycles different from those in the arrangement shown. For instance a switch SA might be inserted in lead 89 which switch when open would cause progressive plan operation on the A or shortest cycle.

Still other arrangements are readily apparent to those skilled in the art; for example the preventive circuits to the local controller might be replaced by permissive circuits under which transfer of right of way from the main road by each local controller could be made only while the impulse was being received, instead of only while interrupted as in the arrangement shown. Substitution of such permissive circuits would involve a different arrangement of master timer contacts, switches, and change-over relays in lieu of the ones shown.

Under another plan of operation it may be arranged for example to change-over operation of the individual intersection controllers from traffic-actuated controllers of the full or semiactuated type to the fixed time type. Or the controllers could be arranged to insert in their normal signal cycles a pedestrian period when operating on certain coordination plans; for example the pedestrian period could be inserted while the synchronized coordination plan is efiective.

Summarizing it will be seen that cycle selecting equipment according to the present invention is provided in which selection between a plurality of operating cycles for an associated master trafiic signal timer is automatically accomplished in accordance with the level of traffic density as determined by trafiic detectors situatecl at a representative traific sampling point. It is shown that at approximately the two-thirds point in a cyclically repeated counting period test is made by the selector equipment to determine if the volume level of trafiic has attained a predetermined value required for maintenance of the master timer cycle then operating. If such level has already been so reached provision is made to cause operation in the succeeding counting period on the next longer master timer cycle. If such level has not been so attained test is again made at the end of the counting period to determine if the predetermined level for holding the cycle has yet been reached, and if the level has been attained operation of the master time in the succeeding counting period is maintained on the same cycle. If such level has still not been attained, the selector causes operation of the master timer in the next counting period or the next shorter length cycle.

It will be understood that the ratio of the total counting period to the first part of this period up to the time of closure and reopening of cam contacts sl determines the ratio of increase in traffic to step up from any one cycle to the next longer cycle.

In the present embodiment the ratio of trafilc to step up from one cycle to the traffic to hold on that cycle is 3 to 2 on increasing traflic because the contacts sl operate at two-thirds of the full counting period. The actual number of actuations to step up from the cycle is the same as the number to hold on that cycle but the average ratio of actuations per total counting period or per unit time to step up from the cycle is 1 times the rate to hold on that same cycle.

It will also be appreciated that the ratio of capacities of the unit charge condensers on successive cycles determines the ratio of traffic to hold on a given cycle (or step down from such cycle) to traffic to hold on the next lower cycle (or step down from such lower cycle), because the relative capacities of the unit condensers determine the relative weight of each actuation on the successive cycles in charging the cumulative condenser KC.

The counting period part to total ratio and the ratio of capacities of unit charge condensers on successive cycles together determine the sensitivity of the cycle selector to trafiic in shifting forward or back from one cycle to another. If the capacity ratio for the D cycle unit condenser to the 0 cycle unit condenser is' two thirds for example the same as the ratio of the first part to the whole of the counting'period the cycle selector will be quite sensitive to small changes in trafiic in successive counting periods, since the rate of actuations causing step up from C cycle to D cycle will be the same as the rate of actuations determining whether the selector will hold on D cycle or step down to C.

Ordinarily it is desirable to have the cycle selector more stable and less sensitive in shifting back and forth between adjacent cycles for small trafiic changes in successive counting periods, and this can be accomplished by making the capacity ratio somewhat higher than the first part to whole ratio of the counting period. For example if the ratio of capacities of D cycle condenser to the C cycle condenser is threequarters or four-fifths and the counting period ratio is two-thirds as before, then a somewhat lower rate of trafiic actuations per unit time will hold on D cycle than the rate required to step up to it. The same effect on increasing stability can be provided by keeping a two-thirds ratio of condenser capacities and reducing the counting period ratio below two-thirds by causing the closure period of contact sl to occur earlier in the total counting period; but the latter method of increasing stability would provide a wider total trafiic range for minimum to maximum cycle than the former method.

The cycle selector herein has incorporated in it a multi-position stepping switch and operation of the master timer on the latters next longer cycle is obtained by advancing the switch one position. Operation of the master timer on the latters next shorter cycle is secured by advancing the stepping switch rapidly through a number of positions one less than the total number of available cycle lengths whereupon it comes to rest in the position for causing the desired shorter cycle operation. Provision is made for preventing jamming or false operation on the longest and shortest cycles.

An arrangement believed novel is provided in which the condenser gas-discharge tube circuit normally utilized for registering the volume level of traffic also serves, at the end of the counting period, to count off the proper number of automatic forward stepping movements of the stepping switch, when a shortening of master cycle is being effected.

Provision is also made for a relay group which is efiective to change over from one master timer coordination plan to another as from synchronized to progressive operation, or to free local controllers altogether from the master timer when the master timer is being operated on one or another of its available cycle lengths in accordance with traffic requirements.

A slow charging circuit for condenser KC is provided for D. C. plus lead 53, via resistance RR and contact dr'l of relay DR and contact 93 of relay G. The resistance RR is preferably adjustable and arranged so that the circuit can be opened entirely if desired by means of an open tap or auxiliary switch.

This slow charging circuit will be operative only when relay DR is energized and resistance RR may be adjusted to charge condenser KC to flash potential of tube F'C within the first twothirds of the counting period for example if relay DR is continuously energized so that in the latter event the cycle selector will step up in successive counting periods to the maximum cycle; or resistance RR may be adjusted to charge condenser KC to flash potential within the full counting period but after the two-thirds point and thus the selector would remain in its last attained cycle position as long as relay DR remained energized, by continuous actuation for example.

Since this slow charging circuit is effective only during the closed period of contacts dr'! and the latter are normally closed only momentarily by each traffic actuation under ordinary traffic conditions, this circuit need not affect the count ing by successive traffic actuations unless desired. In some circumstances it may be desired to speed up this slow charging effect to bias the cycle selector toward the maximum cycle as traffic density increases and the cumulative length of time of closure of contacts dr'l becomes appreciablewith large numbers of traffic actuations and with probability of a number of long actuations by slowly moving vehicle wheels or temporarily stopped vehicles if traffic should become congested. This circuit also has a protective value in case of continuous actuation by breakdown of a vehicle on the detector or by other cause.

It will be appreciated that the expressions of stepping up and down or forward and backward or the like are used broadly in reference to operation of the selector switch from one cycle position to another. In the present illustrative embodiment a simple standard unidirectional selector switch is employed, which always steps forward but by a novel arrangement is made to step forward five positions to produce the same effect as stepping backward one position. A two-way stepping switch could be employed with separate step forward and step backward magnets but the present arrangement herein disclosed is believed preferable.

It will also be appreciated that the values mentioned herein for the length of the counting period and for the ratio of part to total counting period and the like are illustrative preferred values which have been found desirable in one i.

practical embodiment of the invention, but are not necessarily limiting values. In some cases it might be desirable to employ a counting period of more or less than six minutes for example.

It is to be understood that various other modifications in the structural details, arrangements or physical values of the parts, or changes in the designs herein exemplified may be made without departing from the spirit of the invention as defined by the claims.

I claim:

1. 'Irailic control apparatus for selecting a plurality of traffic signalling plans suitable for and responsive to various amounts of traffic including in combination a switching mechanism having a series of more than two switching positions and connections operative in the respective positions for providing the respective signalling plans, means actuated by trafiic to measure the amount of such traffic, and periodic timing means to reset said trafiic actuated measuring means at the end of a predetermined time period periodically repeated and to maintain said switching mechanism in its then attained position responsive to a predetermined amount of traffic having been measured in such time period and to shift saidswitching mechanism to a preceding position of said series providing a cycle plan corresponding to a lower amount of traiiic responsive to measurement of less than said predetermined amount of traffic in said time period, and means operated by said periodic timing means at a predetermined point in each said time period to shift said mechanism to a succeeding position of said series providing a cycle plan corresponding to a higher amount of traffic responsive only to measurement of at least said predetermined amount of traffic within said time period up to said predetermined point.

2. Traflic control apparatus for adjusting the time length of a trafiic signal control cycle including a selector switch having a plurality of positions to select a plurality of time cycles of different lengths, traffic counting means, periodic timing means for periodically resetting said counting means, means responsive to the counting of a predetermined amount of traffic by said counting means during substantially the whole of the time period of said periodic timing means to maintain said stepping switch in a position which it has already attained, means responsive to the counting of such predetermined amount of traffic by the counting means at a predetermined point in said time period before the end of said time period to step said selector switch ahead one position to provide a longer time cycle, and means responsive to the counting of less than said predetermined amount of traffic by said counting means at the end of said time period to step said selector switch back one position to provide a shorter time cycle.

3. In a traffic control apparatus having a plurality of traffic signalling cycles and a selector device for selecting between said cycles in accordance with amount of traffic, said selecting device comprising a step by step switch having a series of more than two switch positions and providing connections in the respective positions for the several signalling cycles, a traffic actuated device, an accumulator limit devic actuatable toward its limit by saidtrafiic actuated device and operating at its limit responsive only to accumulation of a certain amount of traffic actuation, a cyclic timer device for resetting said accumulator device periodically at the end. of its cycle, and electromagnetic means for stepping said step by step switch from one position to the next, means operating said electromagnetic means to step said step-by-step switch to the next preceding position of said series from any one position responsive to absence of operation of said accumulator device immediately before the end of said time cycle at which such accumulator device is reset, and means operating said electromagnetic means to step said step by step switch to the next succeeding position of said series responsive to operation of said accumulator device considerably before the end of the time cycle of said timing means.

4. A traffic cycle selector switch apparatus comprising a step by step switch having a series of more than two switching positions with connections operated in the respective positions to provide selected trafic signalling cycles, electromagnetic means for stepping said switch from one position to the next, and tramc accumulator means adapted to be actuated by traflic and to be so actuated cumulatively by a series of traffic actuations, a cyclic timer device for periodically resetting said traflic accumulator device, means responsive to operation of said accumulator device to a predetermined cumulative extent by such traffic actuation during a predetermined part of said periodic time. period to operate said electromagnetic means to advance said stepping switch to the next succeeding cycle position of said series, and means responsiveto accumulation of less than a predetermined amount of such traflic actuation by said accumulator within substantially said full periodic time period to operate said electromagnetic means to step said stepping switch to the next preceding cycle position of said series.

5. An automatic selector switch mechanism having a series of more than two switching positions, a cyclic timer device operating continuously in a time cycle in which a momentary pulse is provided near one end of each cycle and an additional momentary pulse is provided in the latter half of such cycle but at a considerable time before the end of, such cycle, a traffic actuated device, an accumulator device connected to b operated cumulatively by actuation of such trafiic actuated device, means responsive to operation of said accumulator device by a predetermined amount of trafiic actuation in substantially the whole of such time cycle of such cyclic timer to shift said selector switch from one position to the next succeeding position of said series upon said second pulse, means responsive to operation of said accumulator device by less than such predetermined amount of trafiic actuation during such time cycle to shift said selector switch to the next preceding position of said series from such one position upon operation of the first mentioned pulse, and connections between said selector switch and said accumulator device to increase the amount of traffic actuation required in said succeeding position for such shift of said mechanism to a second succeeding position following th first succeeding position and to decrease the amount of trafiic actuation so required in said next preceding position.

6. An automatic traflic signal cycle selector switch apparatus including a selector switch having a series of more than two switching positions and connections from the respective positions to provide a plurality of signal cycles respectively, trafiic actuated means, an accumulator device operated progressively by a series of actuations of said traffic actuated means, a cyclic time switch device having one switch operated momentarily at a predetermined point in its time cycle and another switch operated momentarily at a considerably later point in such time cycle, electromagnetic means for shifting said selector switch from one position to another, means connected to said accumulator and to said cyclic timer to operate said electromagnetic means shift said switching mechanism from one position to the next succeeding position of said series re sponsive to sufficient progressive operation of said accumulator and to operation of said one time switch and also to operate said electromagnetic means to shift said mechanism from 'such one position to the next preceding position a predetermined point in its time cycle and another switch operated momentarily at a considerably later point in such time cycle, electric driving means for said selector mechanism, relay means connected to said accumulator to be operated and locked so operated responsive to progressive operation of said accumulator to a pre determined progressive extent by suflicient trafiic actuations, operating circuit means for said driving means controlled by said relay means and said one cyclic timer switch to drive said mechanism one position forward in said series responsive to operation of said relay means and said one switch, further operating circuit means for said driving means controlled by said relay means and said other cyclic timer switch to drive said mechanism one position backward in said series responsive only to operation of said other switch and nonoperaticn of said relay means, and means operated by said cyclic time switch device for resetting said accumulator and releasing said relay means if locked at the end of such time cycle.

8. An automatic trafiic signal cycle selector switch apparatus including a selector switch having a series of more than two switching positions and connections from the respective positions to provide a plurality of signal cycles respectively, traflic actuated means, an accumulator device operated progressively by a series of actuations of said trafiic actuated means, a cyclic timer switch device having one switch operated momentarily at a predetermined point in its time cycle and another switch operated momentarily at a considerably later point in such time cycle, electric driving means for said selector mechanism, relay means connected to said accumulator to be operated and locked so operated responsive to progressive operation of said accumulator to a predetermined progressive extent by sufiicient trafiic actuations, operating circuit means for said driving means controlled by said relay means and said one cyclic timer switch to drive said mechanism one position forward in said series responsive to operation of said relay means and said one switch, further operating circuit means for said driving means controlled by said relay means and said other cyclic timer switch to drive said mechanism one position backward in said series responsive only to operation of said other switch and non-operation of said relay means, and means operated by said cyclic time switch device for resetting said accumulator and releasing said relay means if locked at the end of such time cycle, and circuit means operated respectively in the respective positions of said selector mechanism to increase the number of traflic actuations required to so operate said accumulator in said next forward position and to decrease the number of such actuations in said next backward position.

9. An automatic traflic signal cycle selector switch apparatus including a selector switch having a series of more than two switching positions and connections from the respective positions to provide a plurality of signal cycles respectively, trafiic actuated means, a condenser, means responsive to a series of traffic actuations of said traflic actuated means to vary the charge on said condenser progressively from an initial value toward a final value, relay means operable responsive to the charge on such condenser reaching said final value, a cyclic timer switch device having one switch operated momentarily at a predetermined point in its time cycle and another switch operated momentarily at a considerably later point in such time cycle, electric driving means for said mechanism, operating circuit means for saiddriving means controlled toward said final value responsive to relatively prolonged traffic actuation.

11. An automatic selector switch having a series of more than two switching positions and circuit means connected with the respective positions to provide a plurality of traffic signalling cycles suitable for different amounts of trafiic per unit time, a relatively large condenser, a plurality of relatively small condensers of different values of capacity and connected with the respective positions of said selector switch to be selected thereby, traffic actuated relay means 1 adapted to be actuated momentarily by each of a series of trafiic units and connected to switch said small condenser selected by said selector switch in one position of the latter from connection with a power supply to connection with said large condenser and back to the power supply connection so as to transfer a charge between said condensers and to vary the charge on said large condenser progressively from an initial value toward a final value in accordance 5 with thenumber of such traffic actuations, means operating responsive to the charge on said large condenser reaching said final value, time controlled means operating cyclically at predetermined time intervals to shift said selector switch to the next position backward in said series or to maintain it in the same position or to shift it to the next position forward in said series selectively in accordance with whether said final charge responsive means is non-operated or operated at the end of said time interval or is operated prior to the end of said time interval respectively.

12. An automatic selector switch having more than two switchingpositions and circuit means connected with the respective positions to provide a plurality of trafiic signalling cycles suitable for different amounts of traffic per unit time,a relatively large condenser, a plurality of relatively small condensers of different values of capacity and connected with the respective positions of said selector switch to be selected thereby, traffic actuated relay means adapted to be actuated momentarily by each of a series of traffic units and connected to switch said small condensers selected by said selector switch in one position of the latter from connection with a power supply to connection with said large condenser and back to the power supply connection so as to transfer a charge between said condensers and to vary the charge on said large condenser progressively from an initial value toward a final value in accordance with thenumber of such traffic actuations, means operating responsive to the charge on said large condenser reaching said final value, and time controlled means for controlling shift of said selector switch from one position to another in accordance with operation of said final charge responsive means at periodic time intervals andthereupon to restore the charge on said condenser to its initial value and to release said final charge responsive means from operated condition if operated at such periodic intervals.

13. An automatic selector switch having a series of more than two switching positions and circuit means connected with the respective positions to provide a plurality of traffic signalling cycles suitable for different amounts of trafiic per unit time, a relatively large condenser, a

plurality of relatively small condensers of different values of capacity and connected with the respective positions of said selector switch to be selected thereby, traffic actuated relay means adapted to be actuated momentarily by each of a series of traffic units and connected to switch said small condenser selected by said selector switch in one position of the latter from connection with a power supply to connection with said large condenser and back to the power supply connection so as to transfer a charge between said condensers and to vary the charge 'on said large condenser progressively from an initial value toward a final value in accordance with the number of such traffic actuations, means operating responsive to the charge on said large condenser reaching said final value, time controlled means for restoring the charge on said condenser to said initial value periodically and including means for shifting said selector switch to the next position backward in said series in absence of operation of said final charge responsivemeans prior to such periodic restoration to initial value and means for shifting said selector switch to the next position forward in said series responsive to operation of said final charge responsive means more than a predetermined time before such periodic restoration, both said last named shifting means being ineffective series of more than two switching positions and circuit means connected with the respective positions to provide a plurality of trafiic signalling cycles suitable for different amounts of trafiic per unit 'time, a relatively large condenser, a" plurality of relatively small condensers of different-values of capacity and connected with the respective positions of said selector switch to be selected thereby, trafiic actuated relay means adapted to be actuated momentarily by each of a series of traflic units and connected to switch said small condenser selected by said selector switch in oneposition of the latter from connection with a power supply to connection with said large condenser and back to the power supply connection so as to transfer a charge between said condensers and to vary the charge on said large condenser. progressively from an initial value toward a final value in accordance with the number of such traffic actuations, means operating responsive to the charge on said large condenser reaching. said final value, timing -means for timing a predetermined period and operating to retain said selector switch in the means for restoring said large condenser to its initial charge value shortly after said longer time period.

15. Trafiic control apparatus including a selector switch having a series of more than two positions, circuit means connected with said positions individually to provide a plurality of trafiic signal control timing cycles, a relatively large condenser, a relatively small condenser, a source of charging voltage for said small condenser including a potentiometer for adjustment of the charging voltage, means actuated momentarily by each of a series of units of traific to alternately connect said small condenser to said source and to said large condenser to charge the latter progressively in accordance with the number of such actuations, a discharge tube having a critical voltage for conduction below said source voltage and a relay connected to said large condenser to operate said relay by conduction through said tube when the voltage on said condenser reaches the critical voltage of said tube, and time controlled means for periodically discharging said large condenser to provide successive connecting periods between such periodic dischargings and for controlling operation of said selector switch from one position to another in accordance with the operated and nonoperated conditions of said relay.

16. A cyclic unidirectional step by step selector switch having more than two switching positions and circuit means connected with the respective positions to provide a plurality of traffic signalling cycles suitable for difierent amounts of traflic per unit time, a relatively large condenser, a plurality of relatively small condensers of different values of capacity and connected with the respective positions of said selector switch to be selected thereby, traflic actuated relay means adapted to be actuated momentarily by each of a series of traffic units and connected to switch said small condenser selected by said selector switch in one position of the latter from connection with a power supply to connection with said large condenser and back to the power supply connection so as to transfer a charge between said condensers and to vary the charge on said large condenser progressively from an initial value toward a final value in accordance with the number of such trafiic actuations, relay means connected to be operated responsive to the charge on said large condenser reaching said final value, electromagnetic stepping means operable to advance said selector switch from one position to the next, time controlled switch means operating at periodic time intervals to so operate said electromagnetic means once to advance said selector switch one position responsive to operation of the last named relay means within said time interval, a third relay means operated by said time controlled switch means responsive to non-operation of the charge responsive relay means at the end of such time interval to reset the charge on said large condenser to said initial value and connected to operate said electromagnetic means to advance said selector switch and to be momentarily released and reoperated by each operation of said electromagnetic means to re-operate said electromagnetic means to advance said selector switch step-by-step rapidly, another small condenser, and connections between the third relay means and said condensers to alternately connect said other small condenser to a power supply and to said large condenser to vary the charge on said large condenser with each steping operation of said electromagnetic means progressively toward said final value, and means operated responsive to operation of said final charge responsive relay means to interrupt said third relay means to stop the stepping of said selector switch at the next position back of said one position.

17. Trafiic control apparatus comprising a switching mechanism having a plurality of switches and corresponding switch operating positions, driving means for shifting said mechanism from one position to another, traflic actuated means, a cyclic time switch device operating one of its switches for a brief period at the end of its time cycle and operating a second of its switches for a brief period at a predetermined point intermediate the beginning and end of such cycle, an accumulator switch device connected to said trafiic actuated means to accumulate traffic actuations thereof and to operate its switch responsive to accumulation of sufficient actuations thereof, an operating circuit for said driving means including said accumulator switch and the second of the time switches to shift said switching mechanism from one position to the next responsive to operation of said accumulator switch and said second time switch, another operating circuit for said driving means including said accumulator switch and said first mentioned time switch to shift said mechanism from such next position to said one position responsive to operation of said time switch in absence of operation of said accumulator switch, and connections with the switches of said switching mechanism to provide a plurality of trafiic signal control cycles suitable for various rates of actuation per unit of time.

18. Trailic control apparatus including a cyclic signal controller having a plurality of motor coils operable selectively for operating said cyclic controller through its signal cycle, a cyclic stepping switch having a plurality of positions and connections from each switching position for operating a selected motor coil, a periodic timer device, and means actuated by trafiic to an extent responsive to the amount of such traffic actuation to step said stepping switch from one such position to another to select another motor coil in accordance with the amount of traffic actuation during the period of said periodic timer device.

19. Trafiic control apparatus comprising a plurality of local trafiic signal controllers adapted to accord and interrupt right of way alternately to the main road and cross road at a plurality of intersections of cross roads with a main road individually, a cyclic master controller for controlling the several local controllers as to the time length of their signal cycles and time relation of accord of right of way to one of the roads in successive cycles at the several intersections according to a coordinated plan and providing one plan of coordination to maintain transfer of accord of right of way from one road to the other at the several intersections substantially in synchronism, and providing a plurality of other plans of coordination in which transfer of right of way between the respective roads at the several intersections occurs progressively so that traffic moving long the main road at a suitable speed will be accorded the right of way progressively at the several intersections, and the several plans of such progresisve control providing different gresses along the main road, a selector switch mechanism having a plurality of positions and connections from the respective positions to render effective the several progressive cycle plans and also the synchronized cycle plan, traiiic actuated means along the main road, and time controlled counting means operable responsive to such traiiic actuated means to count traffic over periodic time periods, means responsive to the counting of at least a predetermined amount of traffic in such time period to advance said selector mechanism one position, and means responsive to the counting of less than a predetermined amount of traffic in such time period to shift said mechanism back one position, said selector mechanism having its positions arranged for increased progressive time cycles in successive positions as said mechanism is advanced and to provide the synchronized time cycle in a position following the longest progressive time cycle whereby if the amount of trafiic becomes greater than suited to the longest progressive time cycle the selector mechanism will shift to the synchronized cycle position.

20. In a trafiic control system for a plurality of intersections of cross roads along a main road having local right of way signal controllers at the several intersections and a master controller connected thereto to provide a plurality of cyclic control plans for progressive accord of right of way at the several intersections along the main road through the local signal controllers, and having one cycle plan of synchronized control over such local signal controllers to cause accord of right of way to be made at the several intersections substantially simultaneously, a selector switch mechanism having a plurality of positions and connections corresponding thereto to the master controller to provide such plurality of cycle plans with the several progressive plans arranged to have longer time cycles in several successive positions of said selector mechanism and to have the synchronized cycle position arranged to follow the longest progressive cycle position, time controlled traffic counting mechanism connected to said selector mechanism for counting traffic over a time period and to advance said selector mechanism from one position to another to increase the cycle length responsive to counting more than a predetermined amount of traffic in such time period and means connecting said counting mechanism with several positions of said selector mechanism to increase the predetermined amount of trafiic required to advance said selector mechanism as said selector mechanism is so advanced from one position to another, and means responsive to the counting of less than a smaller amount of traffic proportionate to said predetermined amount of traific to shift said mechanism back to a position providing a shorter time cycle.

JOHN L. BARKER.

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