Steep grade

What it means

This sign warns of a sustained downhill gradient steep enough to change how you must control the vehicle. The percentage describes how much the road drops over a given distance, and the critical fact is the word sustained: a long descent converts gravitational energy into brake heat continuously, and brakes that work perfectly at the top of the hill can fade or fail partway down. The sign appears on mountain descents, canyon roads and steep urban grades, sometimes with an associated runaway-vehicle escape ramp for trucks.

How it gets misread

Drivers often read the percentage as describing the uphill climb only, or believe that riding the brake lightly the whole way down is the careful approach, when that exact habit is what overheats the brakes. Another misread is treating engine braking as hard on the engine.

What to do

Select a lower gear before the descent begins so engine compression carries part of the braking load, and apply the service brake in firm, spaced applications rather than dragging it continuously. If speed builds beyond your target, take a lower gear still. Watch your brake pedal feel through the descent; a softening pedal means the brakes are heating and you should slow earlier and longer at the next opportunity.

Practise this rule

• Brake Failure on a Descent: First Moves | CO

  You press the brake pedal on a long downhill grade and it sinks to the floor with no resistance. What is the first thing you should do?

More warning signs

• Narrow bridge →
• Falling rocks →

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