Overtaking lanes (also called passing lanes) are often a go-to road safety solution for areas with high head-on crash rates. But will the addition of an overtaking lane actually improve safety? 

Firstly, we need to understand that only a very small fraction of head-on crashes occur during overtaking manoeuvres (under 1% of fatal and serious injury crashes according to police coding in Victoria). Also, in a large Austroads study (Espada et al. 2019) it was found that there is significant variation in the impacts of overtaking lanes on safety along a route. While 66% of studied routes had a reduction in crashes, it’s important to note that 34% had an increase in crashes. If you focus this just on the 7kms of the route around the overtaking lanes it shows that half the overtaking lanes decrease crashes, but half INCREASE crashes. 

So, what can we learn from this? 
1. Passing lanes have the potential to improve safety along a route, but they are not the answer to head-on crashes along a route.

2. There may be other benefits to overtaking lanes (decreased frustration, decreased travel times (which is found to only occur in a minor way on lower volume roads), and facilitating central barrier systems), but trying to justify them through a pure road safety benefit is often misleading.  
3. There are key elements to the design of overtaking lanes that impact the safety of the lane itself. These include; merge taper lengths and location, configuration with other overtaking lanes, shoulders widths, geometric design, advanced warning and the presence of barrier systems in the median and roadside. 

Check out the Austroads research: AP-R596-19 Passing Lanes – Safety and Performance. Research confirms benefits of passing lanes | Austroads