GB985427A - Improvements in or relating to road traffic signalling systems - Google Patents

Abstract

985,427. Road traffic signalling systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. Oct. 2, 1961 [Dec. 3, 1960], No. 41664/60. Heading G4Q. In a traffic signalling system for use at road intersections where blocking back is likely to occur, means are provided at an intersection exit which are operative only by vehicles travelling away from the intersection and which provide signals related to the speed of the vehicles, the signals being applied to arrangements which assess the possibility of a queue extending backwardly across the intersection and which if the assessment is that backward extension is likely to occur cause a signalling operation to take place which is effective in preventing the backward extension of the queue across the intersection. It is considered that blocking back of a stream of traffic leaving a junction so as to interfere with the proper flow of traffic through the junction may be caused either by an actual hold up in the exit lane to cause the traffic to halt, or an obstruction such that the traffic only moves very slowly along the exit lane. Embodiments to deal with either of these eventualities are described. An exit detector EDI is placed in the exit lane and feeds pulses to the detector relays DR, which are arranged to provide speed timing and serve to control speed discriminating circuits SDA and SDB. In order to deal with an actual hold up it is assumed that the vehicle to last cross the pads before stopping will be travelling at say 5 mph or less, and at such speeds the discriminating circuit SDA applies a signal to the lead START, which energizes a delay circuit DC. If no further vehicles cross the detector during this delay period the delayed signal is passed to the controller CON to terminate the right of way at the junction to traffic in this considered direction. If however a vehicle crosses the detector at less than 5 mph during the delay period a second registration is set up in the discriminating circuit SDA and this serves to apply a reset signal on the lead RESET to start the delay period again. If a vehicle crosses the detector at more than 5 mph during the delay period, a registration will be made in the discriminating circuit SDB which passes a signal via the CANCEL lead to deenergize the delay. To deal with the case of very slow moving traffic the RESET lead is omitted, and the discriminating circuit SDA is brought into operation at a speed of say 10 mph or less. If a vehicle crosses the detector at more than 10 mph during the delay period the delayed signal will be cancelled, otherwise the controller CON acts as before. The controller may be arranged to affect traffic lights at the junction and/or to illuminate diversion signals at the approach to the junction. Specification 725,475 is referred to.