They're called runaway truck ramps, and they're designed to prevent extremely severe accidents in the event of brake failure. But who exactly are these ramps designed to protect, and how do they work?

Dirt is flying! Narrator: If you've driven any one of the many highways crisscrossing the world, chances are you've seen one of these: a truck escape ramp. Some escape ramps slope upwards.

Dirt is flying! Narrator: If you've driven any one of the many highways crisscrossing the world, chances are you've seen one of these: a truck escape ramp. Some escape ramps slope upwards.

The closure—scheduled from 8 :30 a.m. to 3 p.m. Tuesday—is from the Haiku side of Harano Tunnel to the vicinity of the runaway truck ramp, according to the Hawaii Department of Transportation.

The Maggie Valley Police Department issued more than 40 citations last week for commercial trucks illegally traversing U.S. 19 over Soco Gap. Trucks seeking a detour around the closed section of I-40 ...