US2199574A

US2199574A - Traffic signal system

Info

Publication number: US2199574A
Application number: US185322A
Authority: US
Inventors: Joseph N Paul
Original assignee: AUTOMATIC SIGNAL CORP
Current assignee: AUTOMATIC SIGNAL Corp
Priority date: 1938-01-17
Filing date: 1938-01-17
Publication date: 1940-05-07
Anticipated expiration: 1957-05-07

Description

May 7 1940- J. N. PAUL 2,199,574

TRAFFIC SIGNAL SYSTEM.

// /Z sym 2 *M ATTORNEYS.

Filed Jan. 17, 1938 May 7, 1940.

TRAFFIC slam. SYSTEM mw. s n

INVENTOR. JosfP/f /Y, Pnl/L,

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gm wv May 7, 1940. J. N. PAUL TRAFFIC SIGNAL SYSTEM Filed Jan. 17, 1958 4 Sheets-Sheet 3 SGL IGIIE @m01 um m? m Nm l K? mths a w 1h .TVI

INVENTOR. .fos/rf# A. Fama,

QM MY/w ATTORNEYS.

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J.. N. PAUL TRAFFIC SIGNAL'SYSTEM 4 sheets-Sheet .4

Filed Jan. 17, 1.938

Mnsrax TIMER MN mm ,mm mw.

SECOND/9m* T/MEK Nil/N MHIN 101.5 KUN LE )Y1/N E INVENTOR. BY Jose-fw Afl/749m.

/MJ galla" ATTORNEY 5,

Patented' May 7, 1940 UNITED STATES 'raam-'rc SIGNAL srs'rsM Joseph N. raul, son wayne, Ina., asignar, by mesne assignments, to Automatic Signal Corporation, East Norwalk, Conn., a corporation of Delaware Application January 17, 1938, Serial No. 185,322 l 12 Claims.

This invention relates to a tramc signal system. It is particularly applicable to a coordinated system of signals at successive intersections along a main business street or highway where the traillc on one or more of the cross streets is subject to wide iluctuations in volume. Certain features of the invention, however, are adapted for isolated intersections not included in a coordinated system.

One object of the invention is to prevent unnecessary interruptions in main highway tralc when such interruptions are not required by cross street tramo.

Another object of the invention is to eliminate such unnecessary interruptions without disturbing the coordination of signals at the several intersections of a coordinated system.

In coordinated systems the interruptions to the main street traffic at successive intersections may be timed as nearly as possible to permit uninterrupted passage of a vehicle along the main street at a predetermined speed, or they may occur simultaneously at all cross streets, or simultaneously at alternate cross streets. In each of these types of coordination, it is important that the interruptions to main street tralc at the several intersections take place in timed relation with each other.

A single coordinated system may include intersections at which the cross street carries a substantial volume of traiiic at all times and other intersections at which the cross street carries little or no traiic at certain hours. For any coordinated system, the present invention provides time controlled apparatus for timing at each intersection a succession of periods during which right of way always remains in the highway, said periods at the several intersections being coordinated in any desired time relation. At intersections of the first type mentioned above, these periods are alternated with cross street right of way periods in the usual manner. At intersections of the second type, the main street right of way periods are alternated with potential cross street right of way periods during which right of way may or may not be granted to the cross street, depending upon whether or not a vehicle or vehicles are present in the cross street requiring such right of way. Tramo actuated detectors are placed in the cross streetto indicate the presence of such vehicles and when actuated, they serve to condition the apparatus so that the next potential cross street right of way period becomes an actual right of way period for the cross street. In the absence of such actuation. right of way remains with the main street during the potential period. Obviously, a single coordinated system may include intersections of the second type only, in which case trame actuated means for converting potential right of way periods into actual right of way periods are located at all ofthe intersections. y

For use at an isolated intersection not forming a part of a coordinated system, the invention,

provides means for. timing main street right of way periods alternated with potential cross street right of way periods, together with traiilc actuated means for converting the potential periods into actual right of way periods for the cross street when required by trame.

Other objects and features of the invention will be understood from the accompanying drawings and the following description and claims:

Fig. 1 is a plan view of a main street intersected by a number of cross streets showing a desirable 'location for the trafc signals and traillc actuated devices used to indicate the presence of vehicles in the cross streets.

Fig. 2 is a diagrammatic view of a detector relay used with the particular, type of trame actuated apparatus herein disclosed.

Fig. 3 is a sectional view taken on the line 3 3 of Fig. 4 and showing the construction of a preferred form of traffic actuated device.

Fig. 4 is a longitudinal sectional View of the same.

Figs. 5 and 5a together constitute a diagram showing in a preferred form the wiring for the apparatus controlling the rst four, intersections of Fig. 1; Conductors marked X in Fig. 5 are connected to those marked X".in Fig. 5a. Fig. 6 is a sequence table showing the time of operation of the several switches, signals. etc. for an illustrative sequenceof operations of the apparatus used for the ilrst two intersections of Fig. 1. y

Fig. '7 is a simplified diagram in across-thelin e form of the electrical apparatus for one of.

said intersections.

Inlthe following specification, the invention is illustrated as applied to a coordinated system of the type disclosed in Bechtold Patent No.

1,951,816. However, certain features of it may is controlled from a central point.

In Fig. 1, there is illustrated a main street intersecting several cross streets of which the third and fourth are assumed to be of the first class carrying an appreciable amount of traffic at all times, while the first and second are assumed vto be of the second class carrying little or no traffic at certain hours. Signals L are provided at each intersection to indicate right of way to themain street and cross streets. These signals may be in the form of the well known red, green and amber signal lamps commonly used for the purpose. Tramo actuated detectors D are placed in the cross street approaches to the intersections of*T the second class in position to be actuated by vehicles approaching the intersections but not by vehicles leaving the same. These detectors are preferably of the magnetic type illustrated in detail in Figs. 3 and 4. Other electrical elements shown in Figs. 5 and 5a may be housed in suitable control boxes at convenient points, preferably adjacent the intersections. The individual elements of the apparatus will each be first described in detail.

Trame actuated detectors Each detector (Figs. 3 and 4) includes a core consisting of a bar II of permanently magnetized steel surrounded by a group of soft iron rods I2. Surrounding the rods I2, there are provided a plurality of spools I3 upon each of which there iswound a coil I4 of insulated wire. The coils are electrically connected by conductors I5 and the coil at one end is connected to conductors I6 and I'I leading through a suitable conduit I8 to the control box. The core and coils are enclosed in a pipe I9 of non-magnetic material, preferably the material known commercially as Transita, as marketed by Johns-Manville Sales Corporation for example. Plugs 20 serve to close the ends of the pipe I9 and one of said plugs receives the conduit I8. The core and coils are held in place within the pipe I9 by a filling 2| of a waterproofing material, such as paraffin.

The detectors are buried beneath the pavement or are cast within the concrete paving slab ii' put in position simultaneously with the pavement. Each detector is made suiiiciently long so that a car approaching bthe intersection must pass through at least a part of its magnetic field. The magnetic field of each detector extends beyond the ends of the detector about half the length of the detector itself. A detector six feet long placed centrally in a traflic lane 22 feet wide will be actuated by any car passing in that lane. For narrower lanes, shorter detectors may be used. For wider lanes, two or more detectors preferably are used. For a six-foot detector, preferably three of the coils I4 are used, each about 20 inches long. The magnetized bar II provides a magnetic field, a part of which extends above the highway surface. The soft iron rods I2 increase the permeability of the core and thus increase the change in lines of magnetic force actually threading the coils I4 which results from the passage of a vehicle containing I 2,199,574 are operated by synchronous motors whose speed Detector relays At each of the intersections having traffic actuated detectors there is provided a detector relay shown in diagrammatic form in Fig. 2. The relay unit includes a coil A pivotally mounted in a gap in the field oi a permanent magnet 22 and carrying a needle 23 movable by movement of the coil A in the well known manner of a DfArsonval galvanometer. The needle 23 carries a small armature 24 adapted to engage a stationary contact member 25. Armature 24 is of magnetic material and member 25- is permanently magnetized and thus attracts and holds said armature when the needle 23 is moved sufiiciently to bring the armature into the magnetic field. Armature 24 and contact member 25 together form an electric switch referred to hereinafter as switch a.

Adjacent the switch a there is provided a motor B on the shaft of which there is mounted an insulation block 26 carrying a plurality of strikers 21 each adapted to strike the end of the needle 23 in the rotation of the motor and thus to break the same free from the magnetic contact member 25. 'I'he insulation block also carries a metallic contact plate 28 having a plurality of indentations 29 in the periphery thereof and engaged by the tips of a pair of resilient contact fingers 30 and 3l. So long as both contact tips engage plate 28 current may flow between them. The contact finger 3| is in the path oftravel of the indentations 29 and when one of said indentations engages said finger the electrical connection between said fingers is broken. The fingers 30 and 3I and plate 28 constitute an electric switch hereinafter referred to as switch b.

The coordination of the system is maintained by a. master timer, indicated by name in Fig. 5.

'I'his timer is herein shown as a motor driven Secondary timers At each of the intersections of the second class there is provided a secondary timer indicated by name in Fig. 5 and similar in type to the master timer. Each secondary timer includes an induction disc 34 driven by any one of three motor coils, HI, H2 and H3, and in turn operating a series of cams 35 to open and close a series of switches hI, h2, h3, h4, h5, h6, hl, ht, hs, hIIl and hII in a predetermined sequence. The motor coils HI, H2 and H3 are arranged so that all drive the timer in the same direction and each drives at a speed which may be adjusted as desired.

For intersections of the rst class, there are provided secondary timers indicated by name in Fig. 5a which are similar to those just described for the second class intersections except that certain of the switches are not used.

Relays At each of the second class intersections there are provided a direct current relay C and alternating current relays E and F of the magnetic type. Relay C when energized closes normally open switches cl and c2, relay E when energized closes normally open switches el and e2 and relay F when energized `closes normally open switches fl. f2, f3 and f4 and opens normally closed switch f5.

Signals Power supply Power supply is preferably alternating current of a commercial voltage and frequency and may be supplied from a single pair of power mains or from local power lines at the several intersections, with a separate supply for the master control. In the present example, the latter method is used, the mains for the master controller being indicated Master AC in Fig. and those for the intersections being indicated Local AC.

` A service switch SM is connected to the Master AC mains and supplies a pair of

distributary conductors

36 and 31. Service switches SL are similarly connected to the local AC mains at each intersection and supply

local distributaries

38 and 39. At each of the second class intersections direct current is supplied to distributaries 40 and i6 by a rectifier R supplied with suitable low voltage alternating current from a transformer T connected to the

local distributaries

38 and 39.

Circuits tabulated In describing the wiring connections, conductors are referred to by number only in tracing the circuits of which they form a part. Conductors having more than one branch carry the same reference number throughout their several branches. Circuits are referred to as circuits No. 1,'No. 2, etc. and are identied by number in Fig. 7 for the lrst intersection. The numbered circuits for this intersection are tabulated and traced below for convenience of reference:

Circuit No. 1: D, I6, A, I1, D. Energizes detector relay coil A when detector is actuated.

Circuit No. 2: R, 40, resistance 4l, 42, push button p, I1, A, I6, R. Direct current circuit energizes vcoil A when push button p is pressed by a pedestrian.

Circuit No. 3: R, 40, a, 43, C, I6, R. Direct current circuit for energizing relay C.

Circuit No. 4: SL, 38, h2, 44, e2, 45, ci, 46, B, 39, SL. Energizes motor B.

Circuit No. 5: SL, 38, b, 46, B, 39, SL. Energizes motor B after circuit No. 4 is broken.

Circuit No. 6: SL, 38, hl, 41, c2, 48, E, 39, SL. Energizes relay E.

Circuit No. 7: SL, 38, h9, 49, el, 48, E, 39, SL. Holding circuit for relay E.

Circuit No. 8: SL, 38, hl, 41, cl2, 48, F, 39, SL. Energizes relay F.

Circuit No. 9: SL, 38, h9, 49, el, 48, F, 39, SL. Holding circuit for relay F.

Circuit No. 10: SL, 38, h5, 50, f3, 5|, MR, 39, SL. Displays red stop signal for main street.

Circuit No. 11: SL, 38, h5, 50, f3, 5|, CG, 39, SL. Displays -green go signal Ifor cross street.

Circuit No. 12: SL, 38, h5, 50, h4, 52, f4, 53, CA, 39, SL. Displays amber caution signal for cross street.

Circuit No. 13: SL, 38, h5,- 50. h3, 54. H3, 39, SL. Energizes secondary timer motor coil H3.

Circuit No. 14: SL, 39, h5. 55, ha, 54, H3, 39. SL. Also energizes motor coil H3.

Circuit No. 15: SL, 38, h6, 55, h1, 56, fi, 51. MA, 39, SL. Displays amber caution signalfor main street.

Circuit No. 16: SL, 38,116, 55, f2, 58,CR, 39, SL. Displays red stop signal for cross street.

circuit No. 1v: si., as, fs, sa, can, si.. Also' 'displays cross street stop signal.

'CircuitNo. 18: SL, 38, h6, 55, f2, 58, MG, 39, SL. Displays green go signal for main street.

Circuit No. 19: SL, 38, f5, 58, MG, 39, SL. Also displays main street go signal.

Circuit No. 20: SM, 36, m4, 59, hlll, 60, HI, 31, SM.7 Energizes the secondary timer motor coil HI.

Circuit No. 21: SM, 36, m3, 6I, hl I, 62, H2, 31, SM. Energizes the secondary timer motor coil H2.

Coordination of timer operations The master timer runs continuously since its motor coil M is connected directly across the

distributaries

36 and 31. Its switches are opened and closed in the sequenceshown in Fig. 6 in which shaded areas indicate the portion of the cycle inwhich the several switches are closed. Each of the secondary timers divides the cycle into several periods indicated in Fig. 6--Main idle", Main run, Change, Cross idle and Cross run, followed by a second Change period. Taking the first of the secondary timers as an example and assuming that the cycle starts in the Main idle period, the secondary timer is at rest since none of its motor coils Hl, H2 or H3 is energized. At the endof this period switch m3 in the master timer is closed, completing circuit No. 2| to energize the motor coil H2. The duration of the idle period thus depends upon the speed of operation of the master timer.

'Ihe motor coil H2 runs the secondaryl timer through the Mairr run period at the end of which switch hll is opened to break 'circuit No. 21 and deenergize the motor coil H2. The duration of this period thus depends upon the speed at which the coil H2 is permitted to operate the secondary timer.

Simultaneously with the end of the Main run period switch h8 is closed, completing circuit No. 14 to energize the motor coli H3 which runs the timer through the change period. The duration of the change period depends upon the adjustment of the speed resulting from the operation of coil H3.

At the end of the change period, switches h6 and h are opened to deenergize coil H3. Switch hlll in circuit No. 20 for the coil HI is closed but does not complete the circuit since switch m4 in the master timer is open. 'I'he secondary timer therefore comes to rest and remains so during the Cross idle period.

At the end of the Cross idle period, switch m4 is closed, completing circuit No. 20 for coil HI to run the timer through the Cross run period. At the end of this period, switch hill is' opened to break circuit No. 20 and switch h3 is closed to complete circuit No. 13, switch h5 in this 'circuit having been previously closed. Circuit No. 13 energizes motor coil H3 to run the timer through the second Change period. At the end of this period, switches h5 and h3 are opened to stop the timer in the main idle position and switch hll is closed to condition circuit No. 21 for the next operation of switch m3. The cycle is thus complete.

By the means just described. each secondary timer predetermines a sequence oi timed periods under the control of the master timer. Minor adjustments in the duration of the periods may be made by adjustments of the speed of operation of the secondary timer motor coils Hi, H2 and H3. Major adjustments in the relation of the periods may be made by connecting switches hlll and hll to the several master timer switches. For example, at the second intersection, the times of starting the Main run and Cross run periods are oiset one-half cycle from those of the iirst intersection by connecting switch hlil to switch m3 and switch hil to switch m4. At the third intersection, switches hill and hll are connected by

conductors

63 and 64 to switches ml and m2 respectively, thus off-setting the start of the running periods from those at the iirst intersection by one-fourth of a cycle. At the fourth intersection, the connections are the reverse of those at the third. Whatever the adjustments may be, the periods at each intersection occur in a deiinite timed relation to those at the other intersection. The timing of the entire system may be aiected by varying the speed of the master timer without destroying theV coordination of the system.

Signal operation-second class intersections Signal operation at the second class intersections may be divided into three general cases; Case I, operation in response to a trailic actuation occurring during a Main idle or Main run period; Case II, operation in response to'a trafiic actuation occurring during a Cross idle, Cross run or Change period; and Case III, operation in the absence` of tramo actuations. In the assumed sequence of operations indicated in Fig. 6, Cases I and III are illustrated by the operation at the rst intersection and Case II by the operation at the second intersection.

Casa I.-Tra1ic actuation during Main idle or Main run periods Referring now to the operation at the iirst in- -tersection as indicated in Fig.6,it is assumed that operation begins in the Mlain idle period and that no traffic actuations have occurred for some time previous. Circuits Nos. 17 and 19 are complete to display the green signal for the main street and the red signal for the cross street. Since these circuits do not pass through the switches of the secondary timer, the signals are not at this time under the control of said timer. All other circuits are incomplete except circuit No. 1 in which no current flows until a wdetector D is actuated.

With the apparatus in this condition, it is assumed that a vehicle approaches the intersection in the cross street and actuates one of the detectors D. The resulting electromotive force generated in the detector causes current to ow in circuit No. 1, ilrst in one direction as the vehicle enters the detector magnetic field and then in the other direction as it leaves said eld. This current deiiects coil A and moves needle 23 either directly toward contact member 25 or first away from said member and then toward the same. In either case, the armature 24 is caught by the magnetic contact member 25 and held thereby to close switchl a. It is to be noted that when two detectors are used at an intersection as shown in Fig. l, they are connected in parallel and the actuation of either causes the closing of switch a.

Coil A may also be energized to close switch a by the operation oi' the pedestrian push button switch p which completes circuit No. 2 to supply direct current to coil A. Although only one such push button is shown in the drawing, it is obvious that as many as needed may be connected in parallel.

The closing of switch a completes circuit No. 3 to energize relay C, closing switches cl and c2. The closing of switch cl has no immediate ei'- fect. 'I'he closing of switch c2 completes circuits Nos. 6 and 8 to energize relays E and F respectively, closing switches el, e2, fl, f2, f3 and f4 and opening switch f5. The closing of switches el and e2 has no immediate eiIect. The opening of switch f5 ybreaks circuits Nos. l1 and I9 to the main street go vand cross street stop signals but the closing of switch f2 immediately establishes circuits Nos. 16 and 18 to maintain these signals in their former condition. The operation of the switches fl, f3 and f4 connect the remainder of the lamps to the secondary timer so that it may thereafter control the signals but no circuitsl are immediately completed thereby. Thus a traific actuation occurring during the Main idle period has resulted in an operation of the relay F immediately placing the signals under control of the secondary timer without effecting an immediate change of signals.

Since the condition of the circuits is the same in the Main run period as in the Main idle period, except that motor coil H2 is operating, a ilrst trailic actuation occurring during the Mainrun period has the same effect in immediately transferring control of the signals from switch f5 to the secondary timer without immediate change of signals. Thus, during both the Main idle and Main run periods right of way always remains with the main street irrespective of trafiic actuations.

At the end of the Main run periodv switch hi is closed to complete circuit No. `to display the amber caution signal to the main street during the change period, the main street green and cross street red signals continuing. If desired, a slightly diierent wiring may be used by means of which the main street green signal may be extinguished during this period as is common practice in certain cities. At the same time, switch hi is opened and switch h9 is closed to transfer control of relays E and F from circuits Nos. 6 and 8 to circuits Nos. 7 and 9. If necessary, switch h9 may be closed slightly before switch hi is opened to insure continuity of the relay positions. Thereafter, relays E and E may remain energized when relay C is later released.

At the end of the change period, switches h6 and h1 are opened to extinguish the main street go, cross street red and main street amber signals and switch h5 is closed to complete circuits Nos. lOand 11 for the main street red and cross street .green signals respectively, thus transferring right of, way to the cross street. These signals are displayed throughout the Cross idle and Cross run periods and the second Change period.

Near the end of the Cross run period, switch h2 is momentarily closed to complete circuit No. 4 to start motor B. While circuit No. 4 is still established the operation of' motor B closes switch b by moving plate 28 into contact with iinger 3|, thus completing circuit No. 5 to continue the operation of motor B after circuit No. 4 is broken. Motor B thus continues to operate until plate 28 has moved a quarter turn to bring the next of the notches 29 into 'engagement with nnger 3|, opening switch b and breaking circuit No. 5. In this movement, one o'f the strikers 21 opens switch @breaking circuit No. 3 and releasing the relay C. The detector relay is thus circuits Nos. 7 and 9.

restored to the proper condition to register another traic vdemand from the detector D. The timing of switch h2 is variable and is so adjusted that any vehicle passing the detector too late to enter vthe intersection during the Cross run street green and cross street amber signals, while the closing of switch f5 completes circuits Nos. 17 and 19 to display the main street green and cross street red signals. Thus, by operation of switch h9 control of the signals has been taken from the secondary timer and restored to switch f5. At the same time, switches h4 and h5 are opened and switch h6 is closed so that the main street green and cross street red signals will be continued if control of the signals is returned to the timer by another trafilc demand.

The circuits have now been restored to the condition from which the assumed sequence of operations began.

CASE II.-Operation in response to tragic actua-- tion occurring during cross idle, cross run or change periods Referring now to the Aoperation at the second intersection as indicated in Fig. 6, it is assumed that operation begins in the first Change period and that no traiic actuations have occurred for some time previous. Relay F has not been energized by a traiiic demand and the signals therefore are not under control of the secondary timer. Circuits Nos. 17 and 19 are complete to display the main street green and cross street red signals.

With the circuits in this condition, an actuation of a detector is assumed to occur, resulting in actuation of coil A, closing of switch a and energizing of relay C as previously described and as indicated in Fig. 6. In Fig. 6 the detector actuation is shown in the Cross Idle period 4but the same results are obtained in the Cross run or Change periods. The operation of relay C produces no immediate result since switch hl is open during all of these periods and circuits Nos. 6 and 8 to relays E and F cannot be completed.

Near the end of the Cross Run period switch h2 is momentarily closed as before but cannot complete circuit No. 4 to motor B since relay E has not yet been energized and switch e2 is open. Motor B, therefore, can not operate to open switch a and consequently relay C remains energized.

At the end of the second Change period, switch hl is closed, completing circuits Nos. 6 and 8 and energizing relays E and F. Relay F operates as before to ltransfer control of the signals to the secondary timer. The timer retains controlv` through the succeeding Main idle, Main run, Change, Cross idle, Crossrun and second Change periods, changing the signals as previously described and relinquishing control when switch h9 is opened at the start of the second succeeding CAsn IIL-Operation in the absence of trafic actuations Referring again to the operation at the rst intersection as indicated in Fig. 6, the circuits are in the same condition in the second Main idle period as in the nrst. However, it is assumed that no tramo actuations occur prior to the end` of the Main run period. In that case, relay F remains deenergized throughout the succeeding periods, retaining control of the signals through switch f5 to shown main street green and cross road red signals. The switches of the timer are operated through :their usual cycles but have no effect on the signals since switches fl f2, f3 and f4 are all open. This state of affairs continues as long as no tramo demands are received from the cross street. f

Signal operation-first class intersections The wiring at the first class intersections as shown in Fig. 5a is the same as for the second class intersections except that the detectors, de-

' tector relays, and relays C, E and F are omitted and the signal lamp circuits are connected directly to the switches of the secondary timer in-v stead of passing through the switches of relay F. The secondary timers therefore control the signals at all times and operate them through the same cycle of changes and by the same sequence of switching operations as the secondary timers at the second class intersections do when they are in control of the signals.

Recapitulation--coordnated system Briefly summarized, the master timer and secondary timers provide means for establishing at the first class intersections alternate periods of main street and cross street right of way and at the second class intersections potential periods of cross street right of wayv alternated with main street right of wayperiods. At the first class intersections, the usual cautionary change periods may be provided and at the second class intersections potential cautionary periods maybe provided. The periods at intersections are coordinated in any desired time relation with those at the other intersections. v

At the second class intersections, the secondary timers do not control the signals in the absence of traic on the cross street, said signals in. that case maintaining main street right of way and denying right of way to the cross street. A traffic demand from the cross street occurring during the main street right of way period results in an immediate transfer of signal control to the timer without an immediate change of signals. The timer exercises control until the start of the next main street right of way period and in so doing converts the intervening potential cross road.

right of way period and cautionary periods into actual cross road right of way and cautionary periods; A traflicv demand received during a potential cross road right of way period or one of transfer of control to the timer but said transfer is delayed until the start of the succeeding main street right of way period. Control is relinquished -by the timer at the start of the second succeedingmain street right of way period, the intervening potential periods being converted into actual periods.

Isolated intersections `For use at an isolatedintersection not a part of a coordinated system, the same apparatus is supplied as at the second class intersections except that the master timer is not used. Switches hill and hil are connected direct to the local distributary 38 and the coils HI and H2 are connected to the local distributary 39. l Thus the idle periods of the timer are eliminated and the go periods are timed entirely by the speed resulting from coils- Hi and H2. The timer assumes control of the signals in response to trame demands from the cross street, the signals otherwise maintaining main street right of way exactly as previously described for the second class intersections.

The foregoing specification describes a preferred formof the invention the details of which may be varied by those skilled in the art without departing from the scope thereof as deilned by the appended claims.

The invention claimed is:

1. In a .trailic control system for the intersection of a main street and a cross street, trailc signals, time controlled apparatus operating to time a continuous succession of cycles of potential cross street right of way periods alternated with intermediate periods, relay means normally disconnecting said signals from said apparatus and operating said signals directly to indicate main street right of way in the absence' of trafilc on the cross street, and trailic controlled means connected with said time controlled apparatus and with said relay means to operate the latter to connect said signals to said apparatus in response to the presence of a vehicle approaching the intersection in said cross street to convert the next succeeding potential cross street right of way period into an actual period of right of way for the cross street.

2. A traillc control signal system for the intersection of a main street and a cross street includlng right of way signals, a trafiic actuated detector adapted to be actuated by vehicles approaching the intersection in said cross street, time controlled means operating cyclically for predetermining a continuous succession of spaced potential right of way periods for said cross street, relay means normally maintaining said signals disconnected from said cyclic means and including circuit means operated by said relay means for normally maintaining said signals to indicate right of way to the main street in the absence of1 actuationof said detector, and means responsive to an actuation of said detector for operating.

tersection of a main street and a cross street including right of way signals, a trailic actuated detector adapted to be actuated by vehicles ap- `the potential cautionary periods results in a proaching the intersection in said cross street, time controlled means timingl a continuous succession of cycles'of potential right of way periods for said cross street alternated with intermediate periods. swich means and associated conductors for connecting and disconnecting said time controlled means to control said signals, said time controlled means when so connected operating said signals to grant right of way to the cross street during said potential periods and to deny right of way thereto during said intermediate periods; means controlling said signals to deny right of way to the lcross street when said time controlled means is disconnected, meansoperating in response to an actuation of said detector occurring during at least a part of an intermediate period to immediately operate said switch means to connect said time controlled means to operate said signals, and means associated with said time controlled means and operating said switch means for disconnecting said time controlled means after the end of the next succeeding potential cross street right of way period during which-'right of way is granted to the cross street.

4. A tramc control signal system for the intersection of a main street and a cross street including right of way signals, a traillc actuated detector adapted to be actuated by vehicles approaching the intersection in said cross street, cyclic time controlled means timing a continuous succession of cycles of potential right of way periods for said cross street alternated with intermediate periods, switch means and associated conductors for connecting and disconnecting said time controlled means to control said signals,

said time controlled means when so connected operating said signals to grant right of way to the cross street during said potential periods and to deny right of way thereto during said intermediate periods, means controlling said signals to deny right of way to the cross street when said time controlled means is disconnected, means responsive to an actuation of said detector occ'urring during one of said potential periods and operating said switch means after the end of said one period to connect said time controlled means to operate said signals, and means associated with said time controlled means and operating said switch means for disconnecting said time controlled'means after the end of the next succeeding potential cross street right of way period during which right of way is granted to the cross street.

5. A tramo control signal system for the intersection of a main street and a cross street iny cluding right of way signals, a traffic actuated detector adapted to be actuated by vehicles approaching the intersection in said cross street, cyclic time controlled means timing a continuous succession of time cycles each consisting of a potential right of way period for the cross street, a potential warning period for: the cross street, an. intermediate period and a potential warning period for the main street all in sequence, switch means and associated conductors for connecting said time controlled means to control said signals, said time controlled means when l so connected controlling said signals to grant right of way to the cross street during said potential cross street right of way periods, to display a cautionary signal to the cross street during said potential cross road warning periods, to grant right of way to the main street during said intermediate periods and to display `a cautionary signal to the main street during said potential main street cautionary periods, means controlling said signals to grant right of way to the main street whensaid time controlled means is disconnected, means responsive to an actuation of said detector occurring during that part of a cycle including the potential cross road right of way period and both of said potential warning periods and operating said switch means after the beginning of the first succeeding intermediate period to connect said time controlled means to operate said signals, and means associated with said time controlled means and operating said switch means to disconnect said time controlled means after the beginning of the second succeeding intermediate period.

6. In a coordinated traic control system for the intersections of a main street and a plurality of cross streets, trafc signals at each intersection, time controlled means timing a continuous succession of cycles of spaced potential cross street right of way periods for each of said intersections, said periods at one of said intersections occurring in definite timed relation with those at another of said intersections, traic ac- \tuated detectors at each of said intersections adapted to be actuated by vehicles approaching the intersection in the cross street, relay means normally maintaining the signals at each of said intersections disconnected from said time controlled means and operated directly to indicate Aright of way to the main street in the absence of actuations of the associated detector, and means responsive to an actuation of the detector at each intersection to operate said relay means to connect said signals thereat to said time controlled means to operate the signals at said intersection to indicate right of way to the cross street during only the next succeeding potential right of way period.

7. In a coordinated trailic control system for the intersections of a main street and a plurality of cross streets, trafc signals at each intersection, time controlled means timing a continuous'y succession of cycles of spaced potential cross street right of way periods for each of said intersections, said periods at one of said intersections occurring in definite timed relation with those at another of said intersections, a traic actuated detector at each of said intersections adapted to be actuated by vehicles approaching the intersection in the` cross street, switch means and associated conductors for connecting and disconnecting said time controlled means to control the signals at each intersection, said time control means when so connected operating said signals to grant right of way to the cross street during said potential periods and to deny right of way thereto at other times, means controlling said signals to deny right of way to the cross streets when said time controlled means is disconnected, means` operating in response to an actuation of a detector occurring during at least a -part of an intermediate period for the associated intersection to immediately operate said switch means to connect said time controlled means for operating the signals at said lintersection, and means associated with said time controlled means and operating said switch means for disconnecting said time controlled means after the end of the next succeeding potential cross street right of way period.

8. In a coordinated traic control system for the intersections of a main street and a plurality of cross streets, traflic signals at each intersection, time controlled means timing a continuous succession of cycles of spaced potential cross street right of way periods for each of said intersections, said periods at one of said intersections occurring in definite timed relation with those at Aanother of said intersections, a. traffic actuated detector at each of said intersections adapted to be actuated by vehicles approaching the intersection in the cross street, switch means and associated conductors for connecting and disconnecting said time controlled means to contro-l the signals at each intersection, said time controlled means when so connected operating said signals to grant right of way to the cross street during said potential periods and to deny right of way thereto 'at other times, means controlling said signals to deny right of way to the cross streets when said time controlled means is disconnected, means responsive'to actuation of a detector occurring during oneof said potential periods for the associated intersection and operating said tion, time controlled means timing for eachnintersection a continuous succession of timed cycles each consisting of a potential right of way period for the cross street, a potential warning period for the cross street, an intermediate period and a potential warning period for the main street all in sequence, said time cycles for one intersection having a deiinite time relation with those of another intersection, switch means and associated conductors for connecting said time controlled means to control thesignals at each intersection, said time controlled means when so connected controlling said signals to grant right of way to the cross street during said potential cross street right of way periods to display a cautionary signal to the cross street during said potential cross road warning period, to grant right of way to the main street during said intermediate periods and to display a cautionary signal to the main street during said potential main street cautionary periods, means controlling said signals at each intersection to grant right of way to the main street when saidv time controlled means is disconnected, a traiic actuated detector at each of said intersections adapted to be actuated by vehicles approaching the intersection in the cross street, means responsive to an actuation of a detector occurring during that part of the cycle for the associated intersection including the potential cross road right of way period and both of said potential warning periods and operating' said switch means after the beginning of the first `succeeding intermediate period to connect said time controlled means to operate the signal at said intersection, and means associated with said time controlled means and operating said switch means to disconnect said'time controlled means after the beginning of the second succeeding intermediate period.

10. In a traffic control system for the intersection of a main street and a cross street having right of way trafc signals and circuits for energizing the same, means responsive to traflic in the cross street, an electric motor operating at a predetermined time rate and a. shaft and switches operated thereby to energize said signal circuits when connected thereto through, continuous successive cycles in each of which right of way is accorded for` time periods to the main and cross streets alternately; relay means connected with said signal circuits and switches to control connection of the latter and having a normal deenergized condition to disconnect said circuits from said switches and to energize directly the main street right of way signals and said relay means having an energized condition to interrupt direct energization of said main street right of way sign als and to connect said circuits to said switches, and an operating circuit for said relay means connected with said traffic responsive means and including a switch closed by said shaft in its main street right of way period to energize said relay means during Athe latter period responsive to traic on the crossroad, and an auxiliary circuit for said relay means including a switch operated by said shaft to maintain said relay means so energized through the cycle until the beginning of the following main street right of way period.

l1. In a traiiic control system for the intersection of a main street and a cross street having go, stop and cautionary signals for the main and cross streets respectively and circuits therefor, traflic actuated means in the cross street, an electric motor operating at'a predetermined time rate and a shaft and switches operated thereby to energize said signal circuits when connected thereto in continuously repeated time cycles inv cluding a right of way period for the main street,

a potential cautionary change period for the main street, a potential right of way period for the cross street and a potential cautionary change period for the cross street all in sequence in each cycle, other switches interposed in said signal circuits, electromagnetic means operating said other switches when deenergized to interrupt connection between the signal circuits and the switches of said mechanism and to connect the main street "go signal and cross street stop signal directly to a power supply to energize the same, and said electromagnetic means when energized connecting said circuits only to the switches of said mechanism, and means operating responsive to actuation of said tramo actuated means to energize said electromagnetic means in said main street right of way period, said last named means including a switch closed by actuation of said traflic actuated means, a switch closed by said shaft in the main street right of way period and a circuit through said switches for energizing said electromagnetic means when closed, and

through the main street caution period and the' cross street right of way and caution periods.

12. A tramo control signal system for the intersection of a main street and a cross street including right of way signals, a traffic actuated detector adapted to be actuated by vehicles approaching the intersection in said cross street, time controlled means timing a continuous succession of cycles of potential right of way periods for said cross street alternated with intermediate periods, switch means and associated conductors for connecting and disconnecting said time controlled means to control said signals, said time controlled means when so connected operating said signals to grant right of way to the cross street during said potential periods and to deny right of way during said lintermediate periods, circuit means for operating said signals to grant right of way to the main street and deny right of way to the cross street when energized, relay means having a normal unoperated condition for energizing said circuit means and for controlling said switch means in such normal condition to maintain said signals disconnected from said time controlled means, and having an operated condition for deenergizing said circuit means and connecting said signals to said time controlled means, an operating circuit for said relay means including a switch device closed by actuation of said detector and a switch closed by said time controlled means only during said intermediate period, a holding circuit for said relay means including a switch closed by said time controlled means only in said cross street potential right of way period, and a holding device for maintaining said switch device operated after actuation until right of way is granted to the cross street in response to such actuation, releasing means for said holding device and an operating circuit for said releasing means including a switch closed by said time controlled means only near the end of said cross street potential right of way period and a switch closed by said relay means in the energized condition of the latter.

JOSEPH N. PAUL.