Use of coordinated signal settings to reduce junction spill-back

Situations in which a queue grows so as to block the entrance to the link at an upstream junction can cause various problems, including loss of junction capacity, increased driver stress and hazards to pedestrians crossing at the junction. In the worst case the spill-back may grow so as to produce grid-lock within a network. This paper describes word conducted in order to assess how the coordination of junction offsets in a congested network may help to minimise this disruption. A computer model was produced which used traditional speed-flow theory to represent traffic behaviour, eg traffic speeds, merging of traffic and queue evolution. Two test sites were selected for simulation purposes. The first is a three junction linear network whilst the second is a seven junction grid network. These simulation runs attempted to establish which stage at the upstream junction should be disrupted, given that spill-back was to occur. Results from a field trial on the linear network will be presented to show how the techniques can be applied on-street