In Truck/Tractor-trailer brakes and accident reconstruction,
equipment and machinery expert witness Robert R. Reed writes on ABS anti-lock brakes:
The importance of checking proper operation of the ABS system is that some fleets do not have in house maintenance that can diagnose and repair systems and over the road trucking companies tend to not take trucks/trailers out of service for repair for ABS light that stays on. Bulbs or fuses sometimes disappear from the dash warning light and system. Some veteran drivers remember the late 1970’s and don’t care for ABS because they think they have more skill in braking than ABS. This is not true as the new ABS systems have proven there reliability. Trucks/trailers with ABS problems will revert back to regular braking if any faults exist and the wheel or axle with a problem can skid. This can change or explain a stray skid mark that shows up at a scene. Other problems can develop with ABS with maintenance or lack thereof ABS wheel sensors, wiring, or exciter tone rings can be damaged and cause faults. Some fleets will avoid the costs as the truck still has regular brakes. Most normal stops by trucks/trailers do not involve ABS functions as ABS only releases the brake when skids/lock-up situations are detected but emergency/panic stops involving crash situations need the ABS functions to stop sooner or maneuver. If you encounter the unusual check for proper ABS functions.