This study was concerned with the effects of an urban traffic control (UTC) system which came into operation in May 1979 in the central area of Bangkok. `Before and after' surveys were carried out so that the effects of UTC on car and bus travel times and on drivers' compliance with red traffic signals could be investigated. Changes in traffic demand between the `before' and the `after' studies were small, enabling valid comparisons of system performance to be made. In general it was found that there was considerable reduction in average travel time, except for the period 0700 hrs to 0900 hrs. Reductions in stopped time and number of stops were also recorded for all periods of the day other than 0700 hrs to 0900 hrs. In addition, bus travel times on selected routes were reduced substantially. Journey time variability, which is large in Bangkok, was not affected by the UTC. The results of this study of drivers' compliance with traffic signals were inconclusive, and no conclusions could therefore be drawn about the effects of the UTC on this aspect of road safety. (A)

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