An investigation of the capacity implications of installing Advanced Stop Lines (ASLs) has been carried out by TRL Limited as part of a project entitled Cycling Facilities and Engineering, commissioned by the Charging and Local Transport Division of the Department for Transport. The study included a review of previous research into ASLs in the UK and in the Netherlands; an examination of the theoretical capacity implications of installing ASLs using OSCADY (Optimised Signal Capacity and Delay) the signal-controlled junction modelling computer programme and saturation flow formulae; 'before' and 'after' video surveys of modified junctions at four sites in Guildford, Surrey, and questionnaires to examine the attitudes of cyclists. While cyclists generally thought that the ASLs were safer and easier to use than unadapted junctions, concerns were expressed that some drivers did not comply with the new layout. Changes in the length of time between green signals or a longer minimum green time may be required in some circumstances. At the two sites where the number of traffic lanes remained the same there was a slight increase in saturation flow, but at the two sites where a traffic lane was removed large reductions in saturation flow were observed. This report of the study concludes with several recommendations.
Abstract