Traffic signals in urban areas are often coordinated (linked) together on 'fixed time' plans that are pre-set to suit average conditions. 'Scoot' (split, cycle and offset optimisation technique) is a new method of coordination that adjusts the signal timings in frequent, small increments to match the latest traffic situation. Data from vehicle detectors are analysed by an on-line computer which contains programs that calculate and implement those timings that are predicted to minimise congestion. Scoot is designed for general application within computerised urban traffic control systems. The research and development of scoot has been carried out by TRRL and the department of transport and industry in collaboration with the ferranti, gec and plessey traffic systems companies. As part of this work, scoot systems have been implemented in Glasgow and Coventry and traffic surveys have been conducted by TRRL on a total of 62 signals. It is concluded that scoot reduces vehicle delay by an average of about 12 per cent compared with up-to-date optimised fixed time plans; further substantial benefits are likely where, as is often the case, the fixed time plans are based on old traffic data. (Author/publisher)
Abstract