GB1180022A - Improvements in Traffic Control Systems. - Google Patents

Abstract

1,180,022. Traffic control systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. 24 July, 1967 [28 April, 1966], No. 18765/66. Heading G4Q. Traffic in a section of road used as a reservoir area for vehicles intending to use a particular channel subject to delay, e.g. through a toll booth or tunnel, is controlled by signals operated from a central control station whose input is from a detector just within the section on the entering side and from other similar detectors in adjacent sections of the road; the control station acts to prevent traffic from entering the section when it is approaching saturation, as indicated by vehicles coming to rest in the vicinity of the detector, so that a gap is left to permit movement of conflicting traffic, e.g. on cross-roads. Fig. 3 shows a plurality of such road sections I, II and III with intersections controlled by lights of which SR1, SR2 control traffic queuing for the tunnel while SN1, SN2 relate to parallel lanes for traffic not using the tunnel. There may be more than one tunnel lane (Fig. 2, not shown). At a central station are a data channeller D.C. and computer COM, while at each intersection are a master controller for the lights SN and a sub-controller ST for the lights SR and for signs permitting turning from the side roads into the queuing lane (Fig. 4, not shown). The central station also contains a mimic display with lamps indicating the state of the traffic signals and the data stored in the channeller D.C. Detector loops A2 and B2 signal the presence of vehicles, and a timer T is started when A2 is energized and stopped when B2 is energized. If this time is greater than a predetermined value, i.e. the average speed is below a critical value, queuing is indicated and signalled to the computer along line QS. The computer also receives information of vehicles entering the section at E2 and leaving it at passage detectors E3, and adjusts the predetermined time value accordingly. If appropriate, an inhibiting signal is sent along line IS to the sub-controller ST1 to prevent the lights SR1 from going green. It is permissible for the other lane light SN1 to be green when SR1 is red, but never vice versa. The inhibit signal should not shorten the green period of SR1 below a dangerous minimum but should then inhibit the next change to green. In the intervals of scanning the exit detector E3 and the lights SN2 and SR2 the computer performs other functions, viz: reading the queue detectors A2 and B2, calculating the inhibit time, transmitting the inhibit signals, updating the mimic display and printing out information, A practical intersection is described (Fig. 5, not shown) embodying the above principles. with a series of toll booths the exits from which are also monitored. Provision is made for pedestrian crossings at the entrance to the queuing area and for traffic turning out of the queuing lanes into side streets, which also may have queues for the same toll booths.