D.C. Mun. Regs. tit. 18, r. 18-758
Commercial motor vehicles registered in the District with a manufacturer's gross vehicle weight rating exceeding ten thousand pounds (10,000 lbs.) shall be equipped with a side guard. The requirement imposed by this subsection shall apply twenty- four (24) months after the effective date of this subsection.
Pursuant to US Department of Transportation Volpe Side Guard Standard (US DOT Standard DOT-VNTSC-OSTR-16-05:
(https://rosap.ntl.bts.gov/view/dot/12371), side guards shall allow for a maximum thirteen-point-eight inch (13.8") ground clearance, maximum thirteen-point-eight inch (13.8") top clearance; be up to four feet (4') in height; and have a minimum impact strength of four hundred and forty pounds (440 lbs.); achieve a smooth and continuous longitudinal (forward to backward) impact surface flush with the vehicle sidewall. Side guards may include rail style guards, provided that such rails shall be no less than four inches (4") tall and no more than eleven-point-eight inches (11.8") apart; and may incorporate other vehicle features such as tool boxes and ladders.
D.C. Mun. Regs. tit. 18, r. 18-758