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If you’ve ever driven through the mountains, you may have noticed strange-looking off-ramps on the downhill slopes. These short-ish dirt roads seem like an afterthought going nowhere. But to drivers of semi-trucks, they’re a well-thought-out safety system that saves lives. Dirt off-ramps are actually runaway truck ramps and are designed to stop a vehicle that’s barreling out of control. Let’s take a look at how they work and how drivers use them.

What is a runaway truck ramp? 

A highway sign shows the distance to the nearest runaway truck ramp.
A highway sign displays the distance to a runaway truck ramp | Robert Alexander/Getty

The Interstate highway system was developed to provide a faster, safer way to drive across the country. As the Interstate highway system expanded, so did commercial trucking. But more trucks mean more risks for accidents, which led highway engineers to design more safety systems, including the runaway truck ramp. According to J.D. Power, these ramps made their debut in the 1960s.

There are several types of runaway truck ramps. J.D. Power says the most common ramps are made with deep gravel or sand to quickly slow trucks, bringing them to a stop. Other ramps use wire nets or barriers filled with sand or water. In just about every case, the ramp has an uphill slope to leverage gravity to help slow the truck.

Runaway truck ramps are easy to spot. They look like unfinished highway off-ramps that go nowhere, and they are usually preceded by a yellow highway sign informing drivers of their location.

How do you use a runaway truck ramp? 

There’s not much to using a truck ramp. If you are unable to control your speed, the important thing is to stay calm and look for ways to slow down rather than coasting, like engine braking or using the jake brake. You may not be able to stop, but you might be able to keep from speeding up on a downgrade.

Once you see a truck ramp, line up with it and continue trying to slow the truck. You don’t want to jerk the wheel or make any sudden movements that could cause you to lose control completely. Center the truck to the middle of the ramp and keep a firm grip on the steering wheel. It may be hard to keep the wheels straight when you hit sand or gravel.

After you hit the runaway ramp, keep the steering wheel as straight as possible and let physics do the rest. The truck will quickly slow down and slide to a halt.  

Will a truck driver get fined for using a runaway truck ramp?

If the truck driver is unable to slow down or stop their truck and uses the runaway truck ramp for an emergency, they won’t get fined. Using a runaway truck ramp is not only a much safer option than trying to stop on the highway, but it’s also less expensive in cases where physical damage is the result. In general, a runaway truck ramp will cause less damage to a truck than a collision on the highway.

Car and Driver says that states decide how many, where, and what kind of runaway off-ramps to install. There are hundreds of runaway truck ramps in the U.S. spread out at regular intervals on interstates and major highways. They play a critical role in helping to ensure the safety of truck drivers and motorists on mountain passes. Thanks to modern brakes and other safety features on trucks, these ramps are rarely used but invaluable when needed.