Crash injuries reduce 16 per cent after extra lane installation
It may seem obvious to anyone stuck behind a slow vehicle for long periods without a realistic overtaking opportunity, but passing lanes on Australian roads reduce driving times and improve driver safety, an Austroads report confirms.
Passing Lanes: Safety and Performance provides guidance in the development of passing lane installation projects by examining their impacts on safety, journey time and user experience.
Passing lanes are acknowledged for breaking up ‘traffic platoons’ and improving traffic flow over a section of road, sometimes providing the only practical chance for overtaking.
Importantly, passing lanes result in safety improvements, including perceived safety by motorists, safer operational conditions, and crash reductions, the report finds.
Before-and-after crash analysis of routes where passing lanes were installed showed an average reduction of injury crashes by 16 per cent, the peak road and traffic organisation says.
Further, literature on the safety impacts of passing indicates a degree of consensus that passing lanes contribute to the improvement of safety. Injury crash reduction as a result of passing lane installation ranged from 20 per cent to 40 per cent across the documents reviewed.
Passing lanes also improve journey times through a small increase in travel speed and a significant reduction in the proportion of time spent following a slower vehicle. Platooning behind a slow vehicle is a cause of frustration amongst motorists which can then lead to incidents.
Literature demonstrated that motorists consider passing lanes effective and beneficial. A survey of motorists indicated that for the journey experience to be generally acceptable, the per cent time spent following a slow vehicle should be limited to 30 per cent to 40 per cent.
Motorists were also found to attach a value to per cent time spent following of approximately $4 per 100 vehicle-km travelled for every 10 per cent improvement in time spent following.
To assess journey time impacts of passing lanes, numerical experiments were conducted using the traffic simulation model TRARR (or TRAffic on Rural Roads). More information can be found here.