What does a yellow diamond sign with a black truck on a downward slope indicate?

TRUCK GRADE WARNING SIGN: Typically shows a truck icon with a percentage grade and/or an arrow indicating downhill. It warns that a steep descent is ahead — relevant for trucks because: heavy vehicles' brakes can overheat (brake fade) on long steep grades; once brakes fade, the vehicle cannot stop; engine compression braking (downshifting) is the primary speed control technique for trucks on grades. For regular drivers: be aware large trucks may need more stopping distance on grades; downshift on steep hills to reduce brake wear (especially in mountainous terrain); watch for 'RUNAWAY TRUCK RAMP' signs — these indicate escape ramps where runaway trucks can safely leave the road.