General Knowledge · Winter Driving
Why does guidance for driving on icy or snow-covered roads advise against using the engine brake or speed retarder?
Explanation
A driver should avoid using the engine brake or speed retarder on icy or snow-covered roads because both apply braking force directly to the drive wheels, and on a slippery surface that added force can cause the drive wheels to skid, a harder skid to control than one caused by wheel braking alone. This advice about which brake to avoid, and why, is not stated anywhere in 49 CFR; the required-knowledge topic that covers winter driving, 49 CFR 383.111(a)(12)(i) ("bad weather, e.g., snow, ice, sleet, high wind"), names the general topic area but does not specify this technique, so it is standard driver-training guidance rather than a codified federal rule. The other options fail for a shared reason: each invents a requirement or mechanism, a temperature-based federal ban, a faster air reservoir drain, or cold-weather retarder overheating (retarders actually overheat from sustained use generating heat, not from cold), that has nothing to do with why engine brakes and retarders are specifically risky on slippery surfaces.
Source: 49 CFR 383.111(a)(12)(i)
Related Winter Driving questions
- Under 49 CFR 393.75, what is the minimum tread depth required in a major tread groove of a commercial motor vehicle's front (steering) tires, and how does that compare to its other tires?
- Under 49 CFR 383.111(a)(12)(i), which weather conditions does federal regulation specifically name as examples of the "bad weather" a CDL knowledge test must cover?
- Which of the following is a clue that a road surface may be icy even though it does not look wet or icy?
- After driving a commercial motor vehicle through a deep puddle or standing water, why does guidance recommend applying light, steady pressure to the brakes for a short distance afterward?