Effects on Motor Vehicle Behavior of Color and Width of Bicycle Facilities at Signalized Intersections

Abstract

Research was undertaken in Christchurch, New Zealand to investigate motor vehicle behavior near bicycle facilities at signalized intersections. Motorists not keeping clear of such facilities may limit their usefulness and safety for bicyclists. The main research objective was to assess motorists’ avoidance of colored facilities in comparison to uncolored ones. The research also investigated if wide combined bicycle and traffic lanes encourage drivers to queue side-by-side, thereby encroaching into bicyclist spaces. 18 sites were identified to evaluate the effect of colored surfacing and lane widths on the rate at which motorists encroach on marked bicycle spaces. The sites contained either Advanced Stop Lines (ASL) or Advanced Stop Boxes (ASB) and were a mix of colored and uncolored facilities with “narrow” and “wide” lane combinations. Manual surveys were carried out to observe the positions of motor vehicles in relation to the bicycle facilities. Four of the uncolored sites were then colored and “after” surveys conducted. The results showed that drivers were much less likely to encroach on colored bicycle spaces in comparison to uncolored ones, particularly ASLs. Motorists were also more likely to encroach on bicycle lanes in “wide” lane combinations. It is recommended that road agencies continue coloring new and existing bicycle facilities at intersections, with preference given to existing ASLs over ASBs and sites with wider approaches. Traffic and bicycle lane combinations greater than 5.0 m (16½ ft) should also be avoided if separate turning traffic lanes are not present.