General Knowledge · Winter Driving
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?
Explanation
Guidance for driving through deep puddles or standing water recommends applying light, steady brake pressure afterward because it presses the brake linings against the drums or discs, generating friction heat that dries out the water before the brakes are needed for a full stop; water left on the linings can otherwise make the brakes weak, cause them to apply unevenly or grab, or, when pulling a trailer, contribute to a jackknife. This is a driver-training practice, not a codified federal rule; the required-knowledge topic covering winter and wet-weather driving hazards, 49 CFR 383.111(a)(12)(i), names the general topic area but does not specify this drying technique. The other options fail for a shared reason: each invents a mechanism or requirement, recharging the air brake reservoir, a mandatory documented test, or resetting antilock brake calibration, that is not how wet brakes actually recover and is not stated in any federal regulation.
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?
- Why does guidance for driving on icy or snow-covered roads advise against using the engine brake or speed retarder?
- Which of the following is a clue that a road surface may be icy even though it does not look wet or icy?