GB502247A - Improvements in road traffic control systems - Google Patents

Abstract

502,247. Road signals for controlling traffic. SIEMENS & GENERAL ELECTRIC RAILWAY SIGNAL CO., Ltd., DOWNES, F. A., HERWALD, N., and TYACK, F. G. July 7,1937, No. 18874. [Class 118 (ii)] In a system for controlling traffic at an intersection of at least three routes, in one mode of operation, traffic responsive devices in two of the routes are each adapted to effect a demand for a different right-of-way condition, while, in another mode of operation, both of the devices effect a demand for the same rightof-way condition. Thus, when traffic is light, the system may operate on a two-phase basis, and when heavy on a three-phase. The system is described as applied to a three-phase controller of the type described in Specification 427,832, embodying timer circuits of the type set forth in Specification 408,706. The controller may be part of a progressively controlled system such as is described in Specification 450,602, a degree of overlap of traffic conditions being provided to prevent the too frequent change from two-phase to three-phase working and vice versa. The change in number of phases may a a change in the cycle time as determined by the master controller. Three-phase to two-phase working. The controller operates as described in Specification 427,832 and it is assumed that the right-of-way is on road C. The tie line is energized, relays Z, J and relay group JA, JR, JG pulling up in turn, relay CY operating after J followed by relay CZ. prevents the Speed Timer operating during the conversion, also preventing a demand on B road from being effective, while CY and CZ cause an artificial demand to be made to maintain the right-of-way on road C. JA locks up JA, JR, JG and connects the B amber lamps to the A amber lamps; JR recompleting the Speed Timer circuit and connecting the B red lamps to the A red lamps, JG serving the same purpose for the green lamps. The relays associated with road B are now ineffective and the controller operates with two phases, pads in road B being connected in parallel with pads in road A. If right-of-way is not on road C, one of relays AR, BR is normal so that the relay group JA, JR, JG is not energized, when Z and J operate, but CY, CZ operate to give an artificial demand on road C by operating relay CD. Right-of-way passes to road C, when the conversion is completed. Two-phase to three-phase working. When the tie line is de-energized, Z and J release, and if right-of-way is on road C, relay CR will be normal so that JA, JR, JG release. CZ releases followed by CY which is slow to release, so that a pulse is sent to relay RW to maintain the right-of-way on road C until the conversion is completed. If right-of-way is on roads A and B, JA, JR, JG will remain operated as relay CR is operated. Artificial demand relays CZ, CY release to give an artificial demand, operating CD. The Speed Timer operates so that right-of-way passes to road C when the conversion is completed by relays JA, JR, JG releasing.