Patent GB-1019314-A (GB)
Title: Traffic actuated control system
IPC: G08G1/08
Filed: 1962-08-17
Abstract: 1,019,314. Road traffic signals. LABORATORY FOR ELECTRONICS Inc. Aug. 17, 1962 [Aug. 18, 1961], No. 31742/62. Heading G4Q. Vehicle detectors are provided in each traffic lane at an intersection of multi-lane streets and the signals from the detectors are used to calculate the gap between successive vehicles and the average gap. An output signal is produced from a lane timer circuit when the actual gap signal exceeds one of three signals representing average gap, number of vehicles waiting in the other street, and waiting time in the other street, and the last lane timer circuit to produce an output initiates a change in the traffic lights after a vehicle passage period. The operation of the controller is controlled by a six bank ten position line switch, Fig. 2a, of which banks 1 and 2 control the relays ABL and GYL operating the signal lamps 14-19, banks 3 and 4 control relays indicating the state of the controller, and banks 5 and 6 control the timing of the periods. Position 1 is a skip position for phase A, position 2 provides an initial green period, position 3 is a rest position, position 4 is a vehicle period, and position 5 provides a yellow signal for A phase while B phase remains red; positions 6-10 are corresponding positions for the B phase.- The line switch is stepped by a motor magnet MM controlled by relay AS and trigger 20, and the basic timing is determined by the charging of capacitor 30 through the rotor contact of bank 5. In positions 1, 3 and 5 for A phase the charge on the capacitor operates the trigger 20, but in positions 2 and 4 the junction 40 is connected through bank 6 to lines 35A and 34A, respectively, and diode 39 prevents junction 40 rising above the potentials of those lines so that trigger 20 does not operate until allowed by the timing circuits associated with lines 35A and 34A. These timing circuits respectively extend the initial green period in accordance with the number of vehicles waiting and prevent transfer of right-of-way until the actual gap exceeds an allowable gap. Gap measurer and passage timer.-In Fig. 3 a capacitor 100 is charged through resistance 104 and V-3A, and each time a vehicle operated contact DR is closed the capacitor is discharged through diode V-10C to terminal 25 which is connected to negative D.C. The charge on the capacitor therefor represents gap time and provides an output on line 113 through cathode follower V-3B. A neon lamp 114 provides a constant charging voltage to ensure linearity, and a clamping circuit (V-10A and its resistors) prevents the voltage on capacitor 100 rising too high if the gap is large. When the green period is to be ended the terminal 25 is earthed thereby preventing discharge of the capacitors when DR is operated, and the capacitor then times the passage of the last vehicle. Comparator circuit.-The gap voltage on line 113, Fig. 7, is compared with inputs at terminals 150, 160 and 16. The input at terminal 150 is derived from a traffic density measuring circuit, Fig. 4 (not shown), and therefore represents average gap. The input at terminal 160 represents waiting time and is derived from a capacitor which starts charging when the first vehicle in a line is stopped at a red light, Fig. 5 (not shown). At terminal 16 is an input voltage representing the number of ears waiting, derived from a cup-and-bucket circuit, Fig. 6 (not shown). As soon as the voltage on line 113 exceeds one of the other three inputs a corresponding relay DS, TS or CS is energized and earths the cathode of 187. Fig. 7 shows three lane timer circuits having a common output line 36 connected to a trigger circuit, and as long as one of them has not finished timing the line 36 is earthed arid the respective triodes 187 conduct and operate relays NL when their cathodes are earthed. When the last lane timer produces an output the line 36 is no longer earthed, the corresponding relay NL is not operated, and the output trigger circuit fires to operate relay PR which earths terminal 25 of Fig. 3 to allow passage timing on the relevant line 113. The passage time voltage on line 113 passes through V-6A, diode 194 and contacts of relay NL to terminal 34 and position 4 of the sixth bank of the lineswitch (Fig. 2a) to terminate the green period; the voltages on the two other lines 113 are blocked by the open contacts of their associated relays NL. A maximum period timing circuit may be provided, Fig. 10 (not shown), and means may be provided whereby a vehicle actuation received during the vehicle passage time, that is whilst relay PR is operated, is stored to provide another A green period after the B green period, Fig. 11 (not shown). A call is also stored if the passage times on the lines 33 have not all expired when the green period ends.