Patent GB-1151642-A (GB)
Title: Coordination Of Full Actuated Traffic Controllers
IPC: G08G1/082
Filed: 1967-05-22
Abstract: 1,151,642. Road-traffic control. E. W. BLISS CO. 22 May, 1967 [23 May, 1966], No. 23596/67. Heading G4Q. The invention is concerned with a coordination unit for controlling the operation of a full-actuated local traffic controller in an interconnected progressive traffic signal system. Such a unit comprises a timer for deriving a background cycle which is divided into at least two intervals for each signal phase, circuitry responsive during the first interval to condition a phase-termination circuit, and circuitry responsive, at the end of the second interval, to a traffic detector associated with the other phase, for energizing the phase-termination circuit. The invention is described in connection with a system having two successive cross roads (Fig. 1, not shown), each with its own local controller, and traffic detectors in each direction for each phase, the whole being under the control of a master controller which may be pretimed or traffic-controlled. The master controller (Fig. 2, not shown), has three separate synchronizing wheels rotating at different speeds for use under different traffic conditions, and each has three offset selector switches for choosing a particular offset to be used. The co-ordination unit (Fig. 3) is joined to the master controller through these switches 0-1, 0-2, 0-3 and along whichever of these lines is completed by the switch has the power supply interrupted for 3% of a cycle for synchronization. Three co-ordination dials CD-1, CD-2, CD-3 are driven at different speeds by motors M1, M2, M3 and one of these will be in operation depending on which switch DS-2 or DS-3 (in the master controller) is operated. Normally, both switches are open and CD-1 is in operation, this being controlled by units 56 and 58. The switches 0-1, 0-2, 0-3 control circuitry in unit 60 to establish different offsets such as average, inbound preferential or outbound preferential. Unit 60 also synchronizes the motors M1, M2, M3 with the corresponding synchronizing wheels in the master controller by means of the 3% interruption. Each dial (Fig. 4, not shown) consists of a cylindrical drum having a hundred peripheral slots into which eight keys may be placed, the spacing between the keys deciding the durations of the intervals in one cycle. At the beginning of a cycle one of these keys (G) closes switch 70 and advances a stepping switch 74 to close contacts 2 and 3. If the local controller is displaying a right-of-way signal to phase A, switch 34 will be closed and relay CR3 will be energized, holding on through contact CR3-1. This interval lasts for the minimum allowable duration of phase A right-of-way. At the next interval the next key (P1) closes switch 66 and steps the switch 74 to the next position, opening contact 3. If switch 34 is now opened relay CR3 falls off; similarly, if 34 closes during this interval CR3 does not operate. At the next interval key P2 closes switch 66 again and steps switch 74 to the next position closing contact 4. If switch 34 is still closed, a signal along line 32 (indicating detection of a vehicle in phase B) operates relay CR4 whose contacts CR4-1 energize a relay in the local controller (Fig. 2A, see below) to change the traffic signals against phase A and in favour of phase B. When the signals have changed, key P3 will have reached switch 66 and the stepping switch 74 is advanced once more to open contact 4. Key P4 then steps the switch again to close contact 5, and the same sequence of operations (with switch 36 and relays CR5 and CR6) occurs for phase B. After actuation by key P7, the key G operates switch 70 once more and the whole cycle recommences. The relay circuitry shown, and the dials CD with their contacts, may be replaced by solid-state circuitry. Local controller (Fig. 2A). Vehicle detectors D1-D4 sense traffic in the two phases, and may be spot detectors (treadle or magnetic) or pressure detectors (loop or ultrasonic). In the former case memory circuits 30, 32 are provided to store the sensed information. The outputs of these are applied to relay coils CR4 and CR6 in Fig. 3. The phase-operating voltages switched by CR4-1 and CR6-1 in Fig. 3 are applied through maximum timer contacts 42, 50 to operate a relay CR1 or CR2. This closes contacts CR1-1 or CR2-1 to energize a stepping switch 40 or 52 which actuates circuitry 44 or 54 to operate the traffic signals. If the maximum timing is not to be controlled by the co-ordination unit C-1, the switches 42 and 50 are replaced by direct connections, the outputs of the timers 38 and 48 being applied directly to the relay coils CR1 and CR2 respectively.