Passing Opportunities at Slow-Vehicle Bays
Recently ways of assessing the need for and providing for improved passing opportunities on rural two-lane (single-carriageway) highways has been investigated in New Zealand. This paper focuses on studies of the performance of slow-vehicle bays (SVBs), also known as “turnouts.” Field surveys at eight sites identified the effect of different features on SVB usage and on reduction in following. Higher levels of SVB use than reported overseas were observed; however, this use appears to be very dependent on the location and design of each site. The SVBs’ effects on vehicle following was generally not substantial, although the short-term benefits probably reduce driver frustration. Minimum desirable lengths for SVBs were also reviewed, and it was found that the current New Zealand guidelines for SVB lengths may be inappropriate, given the number of merged area conflicts and multivehicle queues SVBs create on the roads. From these findings, project evaluation methods were developed using simplified analytical procedures and a simulation modeling package.