Mountain and Steep-Grade Driving, Speed Management, and Downgrade Braking
Steep grades turn gravity into horsepower. The exam tests whether you pick the right gear before the descent and control speed without overheating the brakes.
Before the descent
Check the brakes at the top and read the signs giving grade percent and length. Select a gear low enough that engine braking holds your speed without the service brakes, using the same gear you would need to climb the grade. Do not coast in neutral, and do not downshift mid-grade once speed has built.
Braking technique
Apply the brakes firmly to shed about 5 to 10 mph, release, and let the engine brake hold. Repeat as needed. Do not ride the brakes, which overheats drums and causes fade. A retarder or engine brake helps, but on wet or icy pavement it can start a drive-axle skid.
Escape ramps
If braking is lost, aim for a runaway truck ramp and use it. Do not try to save the vehicle or the schedule.
Speed management
Observe posted advisory speeds for curves and grades. Slow before a curve, then hold a gentle steady throttle through it.
Worked example
A 6 percent grade runs three miles. The driver crests at 55 mph in high gear and begins braking to hold speed. Within a mile the pedal is soft and hot brake smell is strong. Fade has started. The correct action is to stop at the next safe turnout and let the brakes cool, not to downshift at speed and continue the descent.
Traps
Descending in a higher gear to save time; leaning on the retarder alone; missing the grade sign; braking and steering hard at the same time in a curve; ignoring the escape ramp.