MileCheckWhat steep grade signs mean
A yellow sign warning of a "6% GRADE" and "TRUCKS USE LOWER GEAR" tells you the road ahead drops steeply for a distance. Here's what the percentage means and how to descend safely.
What the percentage means
The number is the road's grade — how many feet it rises or falls per 100 feet of distance. A 6% grade means the road drops 6 feet for every 100 feet you travel. It sounds small, but over several miles it adds up to a long, demanding descent, which is why anything around 5–7% earns a warning sign.
Why the signs warn trucks
A heavy truck descending a long grade builds speed and heats its brakes. Ride the brakes the whole way down and they can overheat and fade — lose their grip entirely. That's why the signs say "trucks use lower gear": gearing down lets the engine do the braking, so the brakes stay cool and ready.
How to descend safely
Whatever you're driving, shift to a lower gear before you start down, not partway through. Let engine braking hold your speed, and use the brakes in firm, brief applications rather than riding them continuously. Keep extra distance from the vehicle ahead — a heavy truck can't slow or stop the way a car can.
Runaway ramps are the backup
On the steepest, longest descents you'll also see signs for a runaway truck ramp — an emergency escape lane for a vehicle that has lost its brakes. Their presence is a signal you're on a serious grade. MileCheck shows your exact mile marker as you descend, so if you ever need to report a problem, you know precisely where you are.
Know exactly where you are — live
MileCheck shows your nearest mile marker in real time as you drive, plus live DOT alerts and the nearest camera on your route. Free to start, works offline, runs on CarPlay and Android Auto.
Questions, answered
What does a 6% grade sign mean?
It means the road descends (or climbs) 6 feet for every 100 feet of horizontal distance. Over several miles that's a long, steep descent, which is why grades around 5–7% get warning signs.
Why do steep grade signs say trucks use lower gear?
Heavy trucks that ride their brakes down a long grade can overheat them until they fade. Shifting to a lower gear lets the engine slow the truck, keeping the brakes cool and effective.
How do you drive down a steep grade safely?
Shift into a lower gear before you start the descent, let engine braking control your speed, apply the brakes in short firm bursts instead of riding them, and leave extra following distance.
What is a runaway truck ramp?
An emergency escape lane on a steep downgrade, filled with loose gravel or sand, that stops a truck whose brakes have failed. Signs warn of them in advance on the steepest descents.