As drivers, we have a hard decision to make when a traffic signal turns from green to yellow. Technically that means come to a stop ASAP, but there are dozens of things that happen when we see that yellow. We have to judge not only whether we can stop in a short enough distance to not be a safety hazard, but whether the car behind us is too close to our back bumper to safely navigate the same stop. Are they paying attention? Are there any cops around?
The Association for Psychological Science calls this split second decision one of the more dangerous encounters on the road. Traffic signal intersection crashes happen literally every day, resulting in millions of bent up cars and hundreds of thousands of injuries, and a significant percentage of which are fatal.