Influence of oncoming traffic on drivers’ decision to overtake cyclists

Paper in proceeding, 2017

Active transportation - such as cycling - can provide health benefits to the population. However, cycling safety remains a major threat to favour the use of bicycles and, for this reason, more efforts are needed to reduce the number of crashes involving cyclists. One scenario which deserves special attention is driver’s overtaking of cyclists since it has an increased likelihood to lead to severe injuries. The decision process for the overtaking manoeuvre is highly influenced by driver’s subjective feeling of risk and the presented driving simulator study aimed to understand how drivers overtake cyclists in the presence of oncoming traffic. Forty-two Japanese participants were recruited to drive on a 16 km long route and were requested to perform eight overtaking manoeuvres of cyclists, with the oncoming vehicle at different values of nominal time to collision in each overtaking manoeuvre. The results showed that the nominal time to collision against the oncoming vehicle had a significant effect on the overtaking strategy (accelerative vs. flying) and on the minimum safety margins towards the bicycle chosen by the overtaking driver. Besides, analysing the data by overtaking strategy, a decrease in minimum safety margins towards the bicycle was found for drivers who opted for a flying overtaking strategy: the drivers who completed the overtaking manoeuvre without letting pass the oncoming traffic reduced their lateral distance to the bicycle when the nominal time to collision decreased. Finally, the current research showed that minimum lateral safety margins were larger in accelerative manoeuvres compared to flying manoeuvres in the most critical overtaking manoeuvre. Overall, the research show that the comfort – and, possibly, the safety – of cyclists might be compromised in overtaking manoeuvres with oncoming traffic. Also, the study provides some implications for the design of active safety systems and automated driving.