Comparative Analysis of Driver Overtaking Behavior Near Low-Speed Automated Vehicles and Human-Driven Vehicles

The first exposure most people will have to fully automated vehicles will be Low-speed Automated Vehicles (LSAVs) on select corridors. LSAVs may disrupt traffic due to their slower speeds and experience increased risky overtaking by nearby drivers which could decrease safety for their occupants and surrounding road users. A field observational study compared driver behavior near an LSAV and a human-driven research vehicle across 94 passes of a 1.3-mile urban downtown route (4 straight and 4 right-turn sections). GEE analyses indicated a higher likelihood of other drivers queuing behind the LSAV when stopped, overtaking the LSAV while turning at signalized intersections, and overtaking the LSAV along straight road segments. To test whether the low speed of the LSAV was the key factor for this difference, 85 participants in a second study watched videos from the perspective of a driver following a simulated LSAV and a simulated passenger vehicle traveling at either low speeds (16 km/h) or high speeds (40 km/h). Once the simulated vehicle stopped midblock at a marked crosswalk, the participants responded whether they would, as a driver, attempt to pass the stopped vehicle. GEE analyses indicated participants were more willing to pass the vehicle if it had been portrayed as driving at a slower speed, irrespective of vehicle type. These results indicate a disruptive effect of LSAVs in mixed traffic and a need to investigate alternative communication signal designs for LSAVs, along with policy changes to mitigate these risks such as regulations on LSAV speeds and traffic separation.