Research was undertaken during 2004/05 to determine the effect of short approach through-lanes and downstream merges on lane use at signalised intersections, and to find ways of improving use. This involved surveying three intersections.
In general, short slip lanes and short approach and departure through-lanes cause short through-lanes to be used less. Accordingly, a guide was prepared to provide preliminary information to assist practitioners to predict and improve short through-lane use.
A direct correlation was identified between short through-lane length and associated lane use. Also, short lane use was substantially less than that estimated by an analytical traffic model. Furthermore, graphs indicated that approach lane length and departure lane length had a similar effect on lane use.
Economic analysis demonstrated that lengthening short through-lanes was economically viable.
Analysis of a short lane on the right showed that it was more likely to be evenly used than a typical short lane on the left. Three alternative short lane configurations were identified which may improve short lane use, involving approaches and/or merges on the right.
Ten signalised intersections were identified that could benefit from lengthening short lanes.
Keywords: analysis, Auckland, benefit/cost analysis, congestion, efficiency, intersections, lane blockage, lane use, layout, short lanes, traffic signals