An escape ramp is intended to be used:

Escape ramps are designed and built for one purpose: to stop a runaway commercial vehicle safely when the driver has lost control of speed on a downgrade. If you find yourself accelerating uncontrollably on a downhill and brakes are not holding, take the escape ramp immediately — do not wait to see if you can recover, and do not worry about traffic, fees, or damage to your truck. An escape ramp will stop you in a fraction of the distance you would travel before crashing if you do not use it. Most escape ramps use deep loose gravel or sand and slope uphill, bringing the vehicle to a stop in 200 to 700 feet. Damage to the truck is usually minor, and there is generally no fine. Hesitation kills.