Towards the Provision of Ultimate Pedestrian Priority: Guidelines for Installation of Scramble (all Red Traffic Phase) Pedestrian Signals at Intersections
S Ahuja, S Bose, T van Vuren, Mott MacDonald, UK; D Ragland, University of California Berkley, US
This research looks at feasibility of providing SCRAMBLE signals which permit the diagonal crossing of pedestrians across the signalised intersection in city centre intersection and proposes guidelines for their installation.
The growing cities of today are faced with an increasing need for mitigation of conflicts between pedestrians and vehicles, especially at major crossings. During peak hours, the combined volume of traffic and pedestrians significantly exceeds the capacity of the intersections, leading to delays for both the pedestrian and vehicles.
Downtown areas in the cities of USA are a good example of this conflict. These areas are dominated by one-way street system, with the left turning vehicles give way to pedestrians. In situations where the pedestrian volumes are high, they lead to long delays for the turning vehicles giving way to pedestrians. In addition pedestrian walking with traffic phase lead to increasing conflicts and reduce safety of pedestrians.
In order to provide higher pedestrian priority and safety, ?SCRAMBLE? signals (all red traffic and all green for pedestrians to encourage safer movements and diagonal shortest paths? have been proposed at typical US downtown intersections. This research looks at feasibility of providing SCRAMBLE signals in city centre intersection and proposes guidelines for their installation.
Scramble crossings, which permit the diagonal crossing of pedestrians across the signalised intersection, have proven to be more efficient in managing the movement of pedestrians at such intersections compared to conventional perpendicular pedestrian crossings. Previous studies (Bechtel and MacLeod, 2003) reveal that the installations of Scramble signals at intersections were able to reduce the frequency of accidents by nearly 50%.
In setting out the guidelines, the paper compares Scramble Signals against the Conventional Pedestrian Crossing, based on the previous studies carried out across the world. The paper also illustrates the fact that, despite having been a subject attracting various studies, no real guidelines has yet been formulated to help practitioners Decide when to install Scramble Signals.
In order to develop operational guidelines, VISSIM microsimulation models of the before and after scramble installation, have been developed. A typical Scramble intersection in downtown Oakland, California and South Kensington, London has been used to test the generic models. The models have been calibrated and validated to the observed traffic behavior. These models have been the run with a variety of pedestrian and vehicular sensitivity test and varying amounts of traffic volumes, level of service, traffic composition, varying pedestrian movements and traffic signal settings.
The study indicates that SCRAMBLE signals are best suited when the pedestrian level of service is greater than C, or the flow rates correspond to 400 pedestrians per hour per direction. The intersection size and the number of pedestrians wishing to cross diagonally also have a major impact on performance of scramble intersections. Where road safety and accident reduction or traffic calming are the objectives Scramble signals prove vital in promoting pedestrian priority and safety in town centre intersections.
Association for European Transport