Bus lanes are commonly interrupted at junctions where they are set back to maintain junction capacity. But in congested conditions this necessitates buses having to queue behind other vehicles in the set-back area, limiting the time advantage accruing from priority schemes. Several possible solutions to this problem are the subject of this study, which includes observations on experimental schemes, and theoretical modelling. At signal-controlled junctions "bus advance areas" have been shown to be effective in reducing bus journey times without significant delays to other traffic, but the details of design are crucial, benefits to be obtained at heavily congested junctions may be limited, and failure to enforce traffic regulations can reduce efficiency. Another trial has shown that bus advance areas may not be appropriate at roundabout junctions. However, a specially developed model suggests that conventional arrangements may be improved by optimising the set-back distance, taking actual flows and capacities into account. The results of the model will be tested in real situations if suitable opportunities arise. The model also suggests that there may be benefits, at appropriate junctions, in eliminating the set-back and terminating the bus lane at the roundabout give-way line, but allowing left-turning traffic to use the last few metres of bus lane. This technique has yet to be tested at a real roundabout, but it has proved successful at a signal controlled junction.
Abstract