"You could design the yellow time so that 90 percent of drivers - or 95 percent -- are not caught in the dilemma zone. But the higher you go, the longer the yellow time is, which increases the time cross traffic is stopped," he says.That would not only increase pollution, Rakha notes, but also the risk of more drivers taking chances to avoid a long light. Other solutions the group suggests could include warning lights that make drivers aware that a green light is about to change, or an in-dash display that communicates with the traffic lights and makes the decision for the driver. Until the day those smarter yellow lights appear, drivers must make their own choices. The safest one is almost always to stop.