Under 49 CFR 393.55, which combination-vehicle components must have antilock brake systems (ABS) if manufactured on or after March 1, 1998?

Explanation

49 CFR 393.55(c)(2) directly names semitrailers, converter dollies, and full trailers as the air-braked commercial motor vehicles, other than truck tractors, which are covered separately by paragraph (c)(1), that must be equipped with ABS meeting FMVSS No. 121 if manufactured on or after March 1, 1998. The WA guide teaches the same manufacture-date threshold for trailing units, so this question rests on the regulation rather than on the guide's wording. Directing the requirement to a tractor axle misdirects to the wrong unit; hazmat cargo and a trailer-length threshold are qualifying conditions that appear nowhere in the regulation, which applies by manufacture date alone.

Source: 49 CFR 393.55(c)(2)