Linking self-driving cars to traffic signals might help pedestrians give them the green light

In a recent study by my team at the University of Michigan, we focused on communication via a vehicle’s driving behavior to study how people might react to self-driving cars in different situations. We set up a virtual-reality simulator that let people experience street intersections and make choices about whether to cross the street. In different simulations, self-driving cars acted either more or less like an aggressive driver. In some cases there was a traffic light controlling the intersection.

In the more aggressive mode, the car would stop abruptly at the last possible second to let the pedestrian cross. In the less aggressive mode, it would begin braking earlier, indicating to pedestrians that it would stop for them. Aggressive driving reduced pedestrians’ trust in the autonomous vehicle and made them less likely to cross the street.

However, this was true only when there was no traffic light. When there was a light, pedestrians focused on the traffic light and usually crossed the street regardless whether the car was driving aggressively. This indicates that pedestrians’ trust of traffic lights outweighs any concerns about how self-driving cars behave.