US2604525A - Traffic control system - Google Patents

Description

y 22, 1952 P. L. ZANNETTOS 2,604,525

TRAFFIC CONTROL SYSTEM Filed March 28, 1949 4 Sheets-Sheet 1 1 I8 *9- Io 35 I I I I 57 I 35 I as r IN VEN TOR.

July 22, 1952 P. ZANNETTOS 2,604,525

TRAFFIC CONTROL SYSTEM Filed March 28, 1949 4 Sheets-Sheet 2 l l/lll 114-1 IN V EN TOR.

l? 22,- 1952 P. ZANNETTOS 2,604,525

TRAFFIC CONTROL SYSTEM Filed March 28, 1949 4 Sheeias-Sheet 5 Q Q M M I -mm y 22, 1952 P. L. ZANNETTOS I 2,604,525

TRAFFIC CONTROL SYSTEM Filed March 28, 1949 4 Sheets-Sheet 4 E F G H L M N o P Q R S 'r INVENTOR.

Patented July 22,- 1952 UNITED. STATES AT TRAFFIC CONTROL SYSTEM Pierre Laerte Zannettos, Westbury,-N. I Application March 28, 1949, Serial No. 83,991

relationship, and toauxiliary signals which op-' crate in predetermined relationship to the time cycle ,of synchro ized or progressive trafiic systems. -1

' In order to permit rapid and convenient movement of automobile traffic in congested areas, progressive trafiicv systems are often employed. In such systems the red and green lights are operated in synchronized. relationship along a.

street. 'Ih'e'period of the cycle is usually con,- stant, but the phase of the operating cycle of each successive light along the'avenue inthe di rection of traffic flow is displaced in time by an amount approximately equal to the time required for an automobile to traverse the distance between the respective lights, provided it travels at the desired synchronization speed. Thus, a particular. series, or train, of, successive green or red lights appears to travel continuously along the street from one end to the other. Ac'

cordingly, automobile traffic, which maintains the same progressive speed as the apparent'speed of the traflic lights, can move without interruption along the street.

Such progressive systems are well known and haveimprovedthe movement of trafiic, but, in practice, have not operated with complete satisfaction for several reasons. In the first place, no simplemethod has been provided to indicate to the motorist whether he is in the leading, middle, or,.trailing portion of the green train Within which he is traveling. Thus, a driverhas no means for eithergaging or correcting his speed relative to the progressive movements of the lights, until he is stopped by a red light. 1 The present invention provides, among other things, rora eommun indication of the relative posij: tion of ana'utomobilewithin the green train, so that a driver, if he finds himself in the trailing 'part of :the green train, may increase his speed slightly, and, if he finds himself in the leading part ofthe train, decrease his speed slightly, thus, in'either case applying corrective measures without being forced to: stop at red light. In addition, this indication is provided in such manner that it can be readily interpreted by the average motorist.

. Another difiiculty with progressive systems is that interference is caused by unsynchronized trafiic along the street. For. example, trafiic which enters the street from a side street and is forcedto stop at the next intersection. If the ing portion of the train will be'iorced: to slow down by the cars which had stopped for the light and are accelerating to gain synchronization speed. Similar interference is-I'caused byt'other.

vehicles that do not travel continuously.v along the street, for example, passenger buses, which cannot maintain the required synchronization speed because of the necessity ior: stopping-ciao pick up and discharge passengers. -11 3' The present invention provides forsecondary. or check-point traffic indicators, havingthe's'ame over-all cyclic period as the progressive system; but which are displaced in time and physicalposition from the nearest lights of the'progressive.

system. These secondary" lights control the unsynchronized tramc so; that it causes the least. interferencewith. the synchronizedtraffic;

Another diificulty'j'is that progressive trafiic systems-- are often established along certain thoroughfares, but with no provision-'for the progressive movement of cross'trafiic. The pres-' entv invention includesprovision for the synchronized movement of trafiic traveling in perpendicular or oblique directions. Moreover, the system is arranged to increase the available park- 'ng space, without appreciably reducing the total traffic movement. 7 l

Accordingly, the present invention provides methods and apparatus for increasing 1 and smoothing the flow of trafiic. One aspect of theinvention relates to secondaryor check-point in-v dicators which have the same total period as the indicators of the progressive system, but

which are displaced in phase, i. e. time, ther 'efrfclmq Such secondary indicators have 'a total period equal to the period'o'f the progressive systemgbut the proportions of time allotted to th'e green and red'is different from that of the' progressive cycle,

and in one embodiment the red 'portion i'sreduced andthe green portion is increasedan'd the light is arranged tohave an effective control position in leading relationship to one-of the traffic indicators of the progressive system, thereby to regulate the movement of unsynchronized trafiic. In another aspect, the invention provides a tra'fiic signal having, the usual indicator lights and in addition an auxiliaryindication for denoting the portion of the green part of the cycle which has elapsed. Thus, the invention provides for the continuous andsmooth movementof trafiic, and

for the simultaneous movement of synchronized traflic in four or'more'directions.v

For example, in accordance with one embodiment of the invention, the trafiic is' regulated in such a manner that trafllc proceeding parallel to a first direction can proceed progressively on adjacent one-way avenues,- and that cross traffic simultaneously proceeding parallel toa second direction may do so progressively and continue ously on predetermined cross-drives;

Other objects and advantages of the present invention will be apparent from a consideration of the following description taken in conjunction with the accompanying drawings, in which: 1

Fig. 1 shows a' series of successive"trafiic'lights having auxiliary indicators; this drawing shows the relationship between these successive lights at one particular instant; H p a, c Fig. 2 represents graphically the cyclic operation of the traffic and auxiliary lights-shown in Fig. 1;.

Fig. 3 illustrates, diagrammatically,"apparatus for operating the trafilc control system of Fig. 1;

Fig. 4 represents, diagrammatically, an intersectionain. a progressive tra'flic system with a secondary ior check-point trafi'ic indicator; displacz'adsin phaseandposition, for controlling unsynchroni'zedtrafilc'; Fig'-.;5 represents, graphically, the operation of theetrafiic and-secondary indicator of Fig; 4.; Fig: 6 shows, diagrammatically, apparatus for controllingjthe traffic" lights shownin'Fig 45;.

Fig. '7 illustrates the arrangement-and-operat ingsequenceof agroup of trafliclights in order to'..obtain*the advantages of'complete trafiic synchronization; and

Fig.3; 8 shows,adiagrammatically, apparatus for operating the .traificlights of Fig. 7 i

In order. tomore' fully explain-theposition and operation of the trafiic control lights,wemay consider the A progressive lights as forming luminous: waves that travel along the. respective Y avenues or streets, and in which the leading part of-;;the --;wave' is represented by p the foremost red stopi signal facing the direction the wave is moving-.1v The red portion of the wave is termed theffred train; the green portionis termed the "green train. Thus; the; red; and green trains move. continuously along 7 the length of the thoroughfare, their lengths depending upon the proportion of red and green lights utilized in the progressive system.

The wave-length pf the luminous. aves; may

beiytalsen as-jhe distance between' the leading points'ofsuccessive red trains on -given avenue,

and may :be measured by the number oistreet intersections over which the wave. extends, or

not maintain p r V a whether lie-should increase, decrease, or hold: eonstanthis present speed.- For.exa'mple, if the driver can knowat all times. the distance .be-

tweenhimself and the nearest red light ahead,

he ean adjust his speed at each intersection and.

travel indefinitely without being .caused to stop by. the lights of the progressive system. V I

. A- trafiiC'lightZKF g'. 1) provides such anindi cation. In order to understand its operation, assumethat light 2 and similarlights' l, 6, 8, l0," l2 and] 4' are. placed. at' successive intersections along a street" and, that green. indicator" l6 and red, indicator ar'efoperatediso .as tojform a progressive traff c system along the street; In thisexample, there'are threeg'reen lights in each green train-and two redlights in each'red' train; Thus, if the entire periodv 1 of v the cycle is '75 seconds, each green lamp; l6 will be illuminated (indicated'in Fig-.1 by the cross-hatching) for 45 seconds (three-fifths M5) at which time the green light will be extinguished and the red lamp recisely") as with a knowledge of i is illuminated for 30 seconds. Each of the trafiie lights 2 to l4 operate in this manner, but the operation of successive traffic lights is displaced in time by seconds sothat traific' fc'ari move continuously along the street providedit'maintains an average speed such that it travels from light to light in 15 seconds. system is conventional and is well known.

In order to enable the driver to regulate his speed to maintain the desired average, three auxiliary indicators 22, 24, and 26 are provided in conjunction with each of the lights. These indicators are connected into the circuits which operate indicators l6 and I8, and by mechanism of well knowntypes, are caused tooperate in the following manner:

of the driver... For example, in Fig. 1, indicator isilluminated one block ahead, as shown by] indicator [8 of traiiic light 4i None'of the auxiliary indicators 22, 24, or 2B are illuminated in trafiic lights 4 or 8, because the'red indicators l8 are illuminated. 1

At, the instant of time under consideration,

greenindicatorflB-of trafiic light 8 has justjbeen' illuminated, the three illuminated auxiliaryfin dicators 22, 24, and

blocks "ahead and that, accordingly, they must maintain or increase, but not decrease, their drivers observing the'single illuminated auxiliary indicator 22 of traffic light'l2' are advised thereby to decrease or hold constant, but not to increase, their speed. Y 7 V V Fig. 2 shows the cyclic operation of the auxiliary indicators 22, .24.;and 2-6 of one of thetra fflcv lights, for*example, traffic light 2,'with re spect to thejcycle of operation of indicators 16 and L8. Line 21' is a time axis, and green indi cato'rll'fi is illuminated during'the time corresponding to the horizontal distance between lines ZQ'andQS'll'. At this time the green is extinguished and red indicator [8 is illuminated for the period of time represented between linestlland 3|. I,

of the green period; Thus, line28, extends from line 29 to line 32 and indicates thatall three'a'ux iliary' indicators are' illuminated; line 33 extend ing from. line 32 to line 34', indicates th'at two' of the auxiliary indicators are illuminated; andline 35 ,'extending.from-line 34 to 36 (corresponding to -the end of the greenperiod at linef30') indi cates that only one ofthe auxiliaryv indicatorsjs' illuminated. '1

It is to be understood that the numbergof' auxil-iary indicators tobe employedwill dependu'pon therparticular trafiic'system and that the greater thejnu'mber of indicators; the nearer the'line s28i 33,,an'd135 will assume the form of line 3'1, which denotes continuous indication;

Fig. ,3 shows schematically an arrangement for operatingthe' trafiiclight 2 with the auxiliary indicators" 22;- 24, and" 26. One terminal o'r-a This part of my Thenumber ofcauxiliary indicators illuminated denotes the distance, for'exarn'ple, the number of blocks or street, intersections, to the nextred' light ahead 7 22 only of, trafi'ic. light 2 is illuminated (note cross-hatching) denoting that a red light.

I a 25 informing the driversfat thisintersection that'the'next red light is three source of power 38 (not shown). is connected by a lead 39 to one terminal of eachof the lamps which illuminate indicators I6 and I8. This terminal' is connected also by a lead 42 to a rotor arm 44 of a selector switch, generally indicated at 46. Arm 44 rotates continuously in a clockwise direction and during three-fifths of each revolution (in this particular example makes contact with a switch segment 48, which is connected to one terminal of an actuating coil 52 of a relay 54;- the opposite terminal of coil-5'2 is connected to power source 38 through a lead 56. Thus,

when rotor arm 44 is in contact with segment 48,

coil 52 is energized, relay arm 58 is moved downwardly to close'ccntacts connecting lead 56 from power source 38, through lead '62, and arm 58 to lead 64. Lead 64 is connected to the lamp whichilluminates green indicator I'6,thus, illuminating the green whenever rotor arm 44 is in contact with segment 48. During the remaining portion of the cycle, relay 54 is in the open position, thus connecting power lead 56 through lead 62, relay arm 58 and lead 66 to the lamp which illuminates the red indicator I8.

The power lead 56 is connected also through lead 68 to one terminal of the lamp which illuminates' auxiliary indicator 22, which is connected in series with the lamps associated with indicators 24 and 26; the opposite terminal of the lamp of indicator 26 being connected by a lead I 2 to a segment 14 of switch 46. Thus, during the first one-third of the green portion of the cycle, all three of the auxiliaryindicators are illuminated.

. During thesecond one-third of the green period, arm '44 makes contact with a switch segment I6, which is connected by a lead I8 and a resistor 82 to cause illumination of auxiliary indicators 22 and 24. During the last one-third of the green period, the switch arm 44 makes contact with a switch segment 84 which is connected through a lead '86 and a resistor 88 to cause illumination of indicator 22. During the red portion of the cycle all auxiliary indicators are extinguished because rotor arm '44 does not make contact with any of the segments.

It is to be understood that the circuit and-apparatus for actuating the auxiliary indicators are of conventional type and commercial equipment can be modified readily toperform the desired functions. The other traflic lights along the street can be actuated by similar switching arrangements in which the rotor arms will be synchronized with arm 44, but will assume various rotational positions (as at 94, 96, 98, and I02) el'ative to arm 44, depending upon theirrespective locations along the street. The above portion of the system provide an advantageous arrangement for-the traflic that is moving continuously along a thoroughfare, but makes no'provision for preventing traflic that is unsynchronized, or which enters the thoroughfare from aside street, from interfering with the free flow of tr-aflic. In order to overcome this difflculty, and in particular toprovide a conveniout control system for public conveyance vehicles such as buses and the like, a secondary traiiic indicator is positioned ahead of each intersection as shown in Fig. 4.

A traflic light, such as that shown at 2 in Fig. 1, is positioned in the usual manner at the intersection of a street I04, which carries the progressive traflic, and a cross street I 06. Traflic which is traveling progressively along this street I04,

in. the di c 9 th ar w. i cq t one by trafiic light 2, with which a stop line I 08 is associated. However,traffic entering this street from the preceding intersection, or unsynchronized traffic such as buses, are controlled by a secondary traific light I'I2 which is equipped with -the usual red and green indicators. A stop line H4 is associated with this trafilc light. The entire cycle of operation of secondary light II2 occupies' the same length of time as the main traffic light 2, but is dipslaced in time therefrom, and the green portion of the cycle occupies a larger proportion of the total period than it does in the main trafilc light 2. Thus, the secondary. tramc light provides a red indication a shortinterval of time preceding the instant whenthe main traijfic light 2 turns from green to red. Advantageously, this difference in time is equal to or a little longer than the time that it would take for trafiic, traveling at the synchronization speed of the progressive system, to pass from stop line II4 to stop line I08. Thus, trafiic which is not sureto pass traflic light 2 while the green indicator is illuminated will be stopped by secondary light 2 at stop line II 4.

The secondary traflic light II 2 changes from red to green before the corresponding change occurs at traffic light 2, and this period of time is such as to permit trafiic which starts from a stationary position at line II4 to reach line I08 substantially at the time trafiic light 2 changes from red to green. This accelerating traffic, of course, requires more time to traverse the distance from line II4 to line I08 than for the synchronized traiiic and therefore the time difference between the auxiliary light H2 and traffic light 2 is greater in' this instance.

Fig. 5 illustrates the sequence of operationof secondary light Il2'with respect to its associated trafiic light 2. The base line I I6 represents a time axis, and the distance between vertical lines H8 and I22 represents that interval during which trafiic light 2 is green, and the interval between lines I22 and I24 represents the time during which traflic light 2 is red, the cycle repeating itself in the usual manner. The horizontal line I26 indicates the interval during which auxiliary light H2 is green, and line I28 indicates the interval during which it is red. It is apparent that light II2 changes from green to red a short interval of time before the corresponding change in traflic light 2. At the time represented by the right-hand end of line I28, secondary light II2 changes from red to green, and it is apparent also that this change occurs at an interval of time preceding the corresponding change in traffic light 2, and that the interval in the latter instance is longer than in the first, thereby to allow for the accelerating trafiic as explained above.

Fig. 6 represents, diagrammatically, the apparatus for controlling the secondary traiiic light H2 in conjunction with trafiic light :2. A motor I32 is arranged to rotate a rotor arm I34 ofa selector switch, generally indicated at I36, continuously in a clockwise direction. Rotor arm I 34 is arranged to make contact with a switch segment. I38 during a portion of its cycle of rotation and with segment I42 durin a different portion of its rotation. The inner segment I 42 is utilized to control the illumination of traflic light 2 and the outer segment I38 controls the illumination of secondary trafiic light II2.

Starting with rotor arm I34 positioned so that it does not make contact with either segment. I38 or I42, actuating coils I 44 and I46 of relays I48 and I52, respectively, are both ie-energized. At

cater-lamp 4-63 of auxiliary 7 this instant aof time, power -supply 38 i is xconnectdthroughlead-15G "to armature I 56 of relay 148;}anelfthi ough lead 1-58 to the .red lamp :"l'8 flf the main trafiic .light'2. Theopposite .ter- {rninal or this lamp is connected through i=1ead l-62-to the power supply 38. p

Lead l54 is also 'connected through armature I64 "of relayi52 and lead .l.66.'.to the Ted-indi- .traflic flight H2; The opposite -terminal of this lamp is connected through alead l'n to :power supply 38.. Thus, bothrelays are .deeenergized andv both tra-ffic lights exhibit a redindication. T

As the-rotor armalSiismoves clockwise, itiirst engages switch i'segment li'ifi' which energizes coil 1 4'6 of:-re1ay -l523th10l1gh a .circuitwhich may he traced as follows: power supplyZ'SB, lead 154, relay coil 1.46,. leadfi'm, rotor. arm I:3.4, ;switch.seg merit 138, and ilead Efl S te the opposite terminal of power supply 3.8; Armature [5410f --rel ay 152 thereby. is icaused to move to its lower position extinguishing-red indicator lamp 168 of auxiliary traffic light'! 22, and energizing green indicator lamp I18 through leads i182 and 1' 2; Thus,=duringthis' interval traffic light 2- gives agreen indication andtraific light 2 continues to exhibit the red indication. a

As the rotor arm 13$ continues to move in a clockwisedirection, it-additionally makes contact with switch segment I42, which energizes coil 144 of relay its to extinguish red indicator lamp 1.8 and energize thegreen indicator lam-p '16 of the main tralfic light 2. Thus, duringthat 'portionhf -therotation of rotor arm M -when it =ma-kescontact with both segments 1 38 and l 42, traific lights 2 and IZ-exhibit a green indication.

Furtherrotation of rotor arm I35 breaks the connection between the rotor arm I34 and switch segment l38, de-energizing relay 152 and changing secondary traffic light H2 from a green to a redindicatiomthe main trafiic light 2 continuing its green indication for a short interval of time until rotor arm l3 l'nolonger makescontact with segment- 42, when both lights again exhibit the red indication. This cycle repeats in synchronism withytheremainder of the progressive ystem. I

Itepparent that the switch segments shown in Figgfi iwhich control the auxiliary lights 22, the-main-traffic light 2, can readily be embodie the switch I36, but have not been shown in thisfigl fe in order to simplify the rawinsey 2 In'the alcove discussion, we have not taken into account-the movement of cross traffic, but Ihaveconsidered o ly the progressive movement of .t ra a ene aimrlev t r hfa n order to-synohrflnize the flQW of traffic along a series of avenues *and --streetssituated perpendicular or oblique to eachother, :I have arr anged.; for the parallel avenues to :carry one-way 'tra-fiic with adjacent avenues carrying traific in opposite directions. 'Moreover I have arranged; the system 30: 3: on c rtain-f t e r r ets w llicarry progressively; moving one-way traffic.

3 la d o: furt erl u r e this sys em of tra-fiic control, consider the example shown in Fig. :7. Traific lanes1U,'V', W; and Z repres ntinorth-isouth avenues, the trafiic on adjacent avenuestraveling in opposite directions, for example, traffic on avenueU travels north, on avenu V it travels south, on 'avenueW it travels north,etc. This'traffic on the north-south avenues,.-is;progressive so that the :traftic' can-move h eontinuously on each of these streetspprovlde'd it maintains an. avera e sneedzwithinpredetermined synchronization limits. 'The .;c10ss'sl1 e t5, -A, 13,10, D, E,.F-.-Q,'R 'S, and T are available to carry the necessary cross trafiic. Inathis'example,every -.t'l'iircl street, thatis A, D, G,.J M, -P,aand.S are termed cross-drives, and carry oneway synchronized crossttraffic, the direction of travel-0n adjacentcross-drives being opposed,';as, for example; .CIOSS-dITiMBS A, G, M, and ,S .are' arranged ':to :carrytrafiic from-West to:east,-.-w hereas tra'ific'son .crossdrives 'D, J, andyP moves from .east to west. The trafiic on each cross-drive moves continuously without interruption.

. The intervening :crosswstreets, for example, 13, .C,:E, F, H,- I,' etc; dognot-carry synchronized traffic,

and are'utilizedfingthe manner :best suited for.

thaparticulartraine -problem. Forexample, they may be; closed to through-traffic and utilized for arking space, loading" and unloading operations, -etc;-,. oritheymayzhe opened to through-traflic in one direction or in both directions. I

As Was-explainedabove, the trails lights, along the avenues, may .be considered as luminous waves that travel along the respective avenues and the leading part ofthe wave may he considered as represented bythe *first. red. signalf-acingthe approaching traf c onthe avenue. Theredtrains onthe avenues areshown in Fig. Tat 182, I84, 185,188,492, -l-9 l,l98,-l98, -202, 29 i, 206, and2fl8. "Thus, the red trains (the intervening space representing-the green portion of thetrains) move continuously alongtheone-way north-south avenues, the length of the red trains, as represented in Fig. '7, depending upon the proportion of red andgreen lights utilized in the progressive systern. Thus, red train 486, inthesparticular posi-e tion shown, would stop-any unsynchronized south boundtraffic onaven-ue V at the intersections with ,streets -H .andI -and the crossedrives G and .J,-;whereas east-westtraffic-on these cross streets and cross-drives H, I, and=J -wouldbe [permitted to -move--.across avenue-V at thatinstant. Eor conveniencein this examplewe can define n; in such manner-that. 4:11 is equal.- tothe numbcrofi intersections incl ded in one. complete cycle, or wave of. lights on the north-south .avjenues WG- n' f-urilher specify that the synchronization speed on the cross-drivesis adjusted. so that the time required. totravellfrom a given intersectiomto the next intersection on-the CIOSSrdIiVB is equal. to the time required to travel onfthe avenue f'rom the. nth. preceding intersection to theintersection with said cross-drive. Q 'In other words -in the present example, n is-givena. value of three :and thefprogressivetraffic speed on; say, cross-drive M is related. .to the synchronization speed on avenue -V so that-asa car moves from avenue U to avenue -V--on: drive M,- a particular point-on the-luminous wave onavenue Vwill have advanced from cross-drive J to cross-drive Thusthe choice ofsynchronization speeds will; fdepend-upon thelengthof the blocks on both ;;the avenuesandstreets.

' Thesystem-mayvbe set i pzfmf ar s a u of ni. idepending upo'n 'the'volumeyof cross trams.

and the: number of drives required to handle thi-s n cross street. For example, if n? *isjmade equal to two; everyrother cross streett-may .carry synchronized one way" cross trafii'c; if*n is *made equal '-'toithree (as in Fig. 7'), then every duration of the crossing timeat the avenues can be increased correspondingly. This arrangement allows a longer crossing time and because of the two-way synchronization increases the eflectiveness of the crossing time.

In the example given, synchronization of the cross-drive traffic can be seen readily by following an imaginary vehicle from west to east alon cross-drive M. The vehicle crosses avenue U as the leading portion of red train I84 reaches the cross-drive M, causing the west-east trafiic lights to exhibit the green or go indication. This is at a time when traffic and signals on all of the avenues will have the positions shown in Fig. '7. j

During the time the vehicle is advancing along drive M from avenue U to avenue V, the trafllc light indications will have progressed three blocks on theavenues; thus, red train I86 will have moved three blocks to the south (from the position shown) and will reach drive M simultaneously with the vehicle, permitting it to cross avenue V without stopping.

During the time the vehicle is advancing from avenue V to avenue W, the red trains will advance three more intersections on the avenues. Thus, red train I94 will have advanced a total of six blocks from the positions shown and will reach drive M simultaneously with the eastbound vehicle, which may then cross avenue W without changing speed.

, During the time the vehicle progresses along cross-drive M from avenue W to avenue X, the red trains on the avenues will have progressed another three blocks, making a total of nine blocks from the positions shown in Fig. 7. Thus, red train I96 will reach cross-drive M at the same instant as the vehicle, permitting it to continue at a steady speed across avenue X.

During the time the vehicle progresses across drive M from avenue X to avenue Y, the red trains on the avenues will move an additional three blocks in their respective directions. The traflic lights thus will have advanced twelve blocks from their initial positions shown in Fig. 7, and, in this example, will have completed one fullcycle. Thus, the vehicle will reach avenue Y simultaneously with a red train on the avenue. The path of the vehicle may betraced, in a similar manner, the remainder of the distance across drive M, and also along the cross-drives A, D, G, J, P, and S in the indicated directions.

It is to be understood that trafilc systems are by their nature subject to considerable variation in order to comply with the invariable constants of a particular area in which the system is to be installed. For example, it is not always possible to locate the cross-drives at exactly modular distances. Some leeway is permissible, depending upon the ratio of red to green lights along the avenues and upon the cyclic constants of the system. If greater variation is necessary, the synchronization speed may be varied along each avenueas required.

. "Although, in the system illustrated in Fig.' 7,

the cross-drives and avenues have been shown in perpendicular relationship, one or more of the streets may be oblique, the synchronization sys- -tem still being applicable under the principles outlined herein. It is also to be noted that streets intervening between the cross-drives may be closed to through traffic, as pointed out above, it follows then that they may be also nonexistent or irregularly spaced. It is apparent also that-the concepts of distance and travel time are 10 largely interchangeablein a discussion of trafIic systems; thus, variations in distance maybe com? pensated by corresponding changes in synchro; nization speeds. a Fig. 8 illustrates diagrammatically a mechanism for operating the traffic lights in this traffic system. The red and green lights are controlled at each intersection by a continuous:- ly rotating cam such as that shown at 2I2 which is provided with a raised portion 2I4. This cam, for example, is used to control traific light 2 which may be considered to be positioned at'the intersection of avenue U and cross-drive J in Fig. "7. Cams 2IB and 2I8 control the traffic lights at the intersections of avenue U with cross streets K and L, respectively, and cams 222, 224, and 226 control the trafflc lights at the intersections of the same streets with avenue V. Motors M are arranged to be driven in synchronism, ior example, by the use of synchronously rotating motors operated from a common alternating cur.- rent supply (not shown). t The traffic lights shown in Fig. 8 are assumed to be those facing the trafl'ic along the avenues U and. V at the above intersections, and it is, of course, understood that the same switch arrangements can be used to control the complementary traffic lights that regulate trafiic movement along the cross streets and the cross-drives. For example, the red lights on the cross streets are merely connected in parallel with the green lights facing the avenue. The raised cam portion 2I4 of cam 2I2 'con.- trols the red indicator lamp I8 of trafiic light. v2 and occupies one-fourth of the circumference of the cam 2 I2, because, in this particular example, the red indicator I8 is illuminated during onefourth of the control cycle. The rate of rotation of the cam 2I2 is'proportional to the desired progressive speed of the trafiic. Thus, one rotation of the cam 2I2 will correspond to a movement'of the luminous wave through twelve intersections on the avenues.

The position of cam 2I2'as shown in Fig. 8 corresponds to the trafiic control condition atthe intersection of avenue U and cross-drive J on Fig. 7. The green indicator being illuminated through a circuit that may be traced from power supply 38 through lead 228, switch arm 232, and lead 234, to one terminal of lamp I5, the opposite terminal being returned to power supply 38 through lead 236. It will be noted that the nearest approaching red train I84 on avenue U is three blocks away, corre ponding to one-fourth of a revolution of cam 2I2. Thus, lamp I 6 will remain illuminated until the raised cam portion 2I4 strikes switch arm 232, the outward movement of which disconnects the green lamp I6 from the power supply 38 and connects red indicator lamp I8 to the power sup ly through'lead 238, switch arm 232, and lead 228. The raised portion of the cam will cause the redindic'ation to be exhibited for a period of time corresponding to the movement of the luminous wave three blocks along the avenue, at which time the indication will change from red to green, to continue the cycle. I Cam 2I6, having a raised portion 242, controls traffic light 4 situated at the intersection of avenue U and cross street K in exactly: the same manner, except/that the raised portion-242 is displaced 30 degrees clockwise, relative tocam 2I4. Thus. as shown in Fig.7, red train I8, I -;has only two blocks to travel before reaching-this intersection. The cam 2I8; which controls; trafstreets, said master trafiic control system comprising progressive traific control systems along each of the main streets of said first series arranged to permit only one-way progressive traffic thereon, said systems being arranged to permit one-way tralfic in opposite directions along adjacent main streets, each of said progressive traffic control systems including a plurality of primary tramc control indicators spaced along said main streets at said intersections and having stop and go indications, each of said progressive control systems includ: ing a plurality of secondary traflic control indicators having go and stop indications, each of said secondary indicators being positioned intermediate said intersections and associated with a primary indicator and spaced ahead of its associated primary indicator along a main street in a direction opposite to that of the progressive one-way traffic thereon and facing the progressive tranic thereon, and switch means arranged to regulate the indications of the primary and secondary indicators and to change the indications of the primary and secondary indicators through repetitive cycles of a predetermined length for each cycle, the cycles of each of the secondary indicators being of the same length as the cycles of the primary indicators associated therewith, the respective cycles of each of said secondary indicators commencing at a time different from that at which the respective cycles of each of the associated primary indicators commence, said cycles of each said secondary indicators having a longer length of time of go indication than the length of time of the go indication of the associated primary indicators.

4. In a traffic control system, the combination comprising a first series of primary traffic lights positioned at intersections along an automobile trailic-way to form a progressiv trafi'ic control system, said primary tramc lights having at least two traific regulating indications, one of said indications being a go indication and one being a stop indication, first switch means for cyclically changing the indications ofeach of these primary traffic lights, a control mechanism operatively connected to said mechanisms arranged to maintain a predetermined synchronizing relationship thereamong, a secondary,

traflic-light associated with and positioned intermediate said intersections and spaced along said train'c-way a predetermined distance ahead of one of said primary trafiic lights of said progressive system in a direction toward the approaching traffic and having go and stop indications facing said approaching traffic, and second switch means arranged to control said secondary traffic-light through cycles equal in duration to the cycles of said associated primary trafiic light in predetermined time relationship therewith and including means for actuating the go indication of said secondary-light for a larger proportion of each cycle of operation of the secondary light than is the go indication of said associated primary trafiic light, whereby automobiles which have been stopped by said secondary light can accelerate before the associated succeeding primary light begins a go indication.

5. A master traffic-control system comprising a first series of adjacent substantially parallel streets, a plurality oi intersections, a first plurality of one-way progressive trafiic systems each having a series of primary traific indicators and being positioned along one of said streets at said intersections, said systems being arranged to permit progressive trafiic movement along the streets of said first series only in opposite directions on adjacent streets, a second series of streets intersecting said first series of streets, a second plurality of non-stop trafiic systems having a series of primary traffic indicators p0- sitioned along said streets of said second series and being arranged to permit non-stop traific movement on adjacent streets of said second series only in opposite directions on adjacent streets thereof, said primary traffic indicators having at least two indications, one of said indications being a go indication, and another of said indications being a stop indication, a third series of streets substantially parallel with said second series of streets and having at least one street thereof positioned between each pair of adjacent streets of said second series, a plurality of secondary trafilc indicators each associated with but spaced ahead of one of said primary trafiic indicators, said secondary trafilc indicators being positioned intermediate said intersections and spaced from the associated primary trafiic indicators along the streets of said first series in a direction opposite to that in which said progressive trafiic movement occurs, each of said secondary indicators having at least two indications facing the progressive traffic, one of said indications being a go and another of said indications being a stop indication, switch means arranged to change the indications of each of the primary traffic indicators positioned along said first series of streets through repetitive time cycles of predetermined length and arranged to change indications of said secondary indicators through repetitive cycles, the cycle of each secondary indicator being of the same length as the cycle of the primary indicator associated therewith, said switch means being arranged to commence the cycles of each of said secondary indicators at a time earlier than that at which the cycles of its associated primary indicators commence, said cycles of each of said secondary indicators having a longer length of time of go indication than the length of time of the go indication of the associated primary indicator, and a master control mechanism arranged to control said switch means to establish a predetermined time relationship among the indications of said progressive control mechanisms whereby constant-speed one-way non-stop traffic movement is permitted on the streets of both said first series and said second series and whereby two-way non-progressive traffic movement is permitted along the streets of said third series.

PIERRE LAERTE ZANNETTOS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,385,807 Wetter July 26, 1921 1,648,629 Taylor Nov. 8, 1927' 1,824,572 Roberts Sept. 22, 1931 1,866,899 Minier July 12, 1932 1,921,423 McCormick Aug. 8, 1933 2,082,479 Buerke June 1, 1937 2,111,087 Beyer Mar. 15, 1938 2,480,290 Fein Aug. 30, 1949

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