Imagine pulling up to a busy intersection and, instead of the usual trio of red, yellow, and green lights, you spot something ...

Rather than doing away with today's traffic signals, Hajbabaie suggests adding a fourth light, perhaps a white one, to indicate when there are enough autonomous vehicles on the road to take charge ...

Some advocates are now pushing to add a white light to traffic lights, specifically for self-driving cars. The white light would signify that an autonomous vehicle is managing traffic flow.