- On the road, the tunnel vision and delayed reactions of each person behind the wheel bring whole highways to a halt. When a car in front does something unusual, drivers often respond by hitting the brakes. That in turn makes the next driver brake. Soon, a wave of commuters are flashing red brake lights.
Humans typically take 3/4 of a second to slam on the brake pedal. Talking on a cell phone can slow response time even more. The delayed reaction creates instability in an otherwise steady stream of traffic.
That's when cars end up bumper to bumper.
"The slow reaction time means people brake more than they should have to," Davis said. "Unnecessary braking–too much slowing down–causes the jam to form in some instances."
The author suggests that adaptive cruise control responds to changing traffic conditions faster than humans. I've heard plenty of good stuff about ACC, but I've also heard that it actually doesn't beat human reaction time.
Related: Why you should just drive straight