If you're driving somewhere this Labor Day weekend, there's a good chance you'll run into a "phantom traffic jam" — a highway slowdown for no apparent reason. It's no one's fault, says Temple mathematician Benjamin Seibold, who studies the phenomenon. At high traffic volumes, any small disturbance in traffic flow can trigger a ripple-effect of drivers hitting the brakes. "There's no outside reason for these traffic jams," he said. "There’s no obstacle on the road. There's no car in the breakdown lane. They're an instability in the traffic flow, so they can occur without any visible reasons." Seibold says individual drivers can mitigate the effects by driving less aggressively and leaving a little more distance from the car in front.