D.C. Mun. Regs. tit. 18, § 1313
1313.1 The following driver's license endorsements shall be displayed on a driver's license in order for the driver to operate certain types of motor vehicles or to operate motor vehicles hauling certain types of cargo:
(a) The Double/Triple Endorsement is required to operate a vehicle designed to pull more than one (1) trailer;
(b) The Transport Passenger Endorsement is required to operate a vehicle that transports more than fifteen (15) passengers;
(c) The School Bus Endorsement is required to operate a school bus or a multi-purpose school vehicle;
(d) The Tank Vehicle Endorsement is required to operate a vehicle that is designed to transport any liquid or gaseous material within a tank that is either permanently or temporarily attached to the vehicle or the chassis. The vehicles include, but are not limited to, cargo tanks and portable tanks, as defined in 39 CFR part 171. However, this definition does not include portable tanks having a rated capacity under one thousand (1,000) gallons;
(e) The Hazardous Material Endorsement is required to operate a vehicle transporting a hazardous material that is required to be placarded under the District of Columbia Hazardous Materials Transportation and Motor carrier Safety Act of 1988, effective March 16, 1989 (D.C. Law 7-190; D.C. Official Code § 8-1401 et seq.), or by the U.S. Secretary of Transportation in accordance with the Hazardous Material Transportation Act, approved January 3, 1975 (88 Stat. 2156; 49 U.S.C. § 1801 et seq. and 49 CFR part 383, § 121);
(f) The Motorcycles Endorsement is required on a Class "A," Class "B," Class "C," or Class "D" driver's license to permit the licensee to operate a motorcycle in addition to the class of vehicles designated on the driver's license;
(g) The Class "A" Commercial Driver's Instruction License Endorsement is required with a Class "B," Class "C," or Class "D" driver's license to permit the licensee to operate a Class "A" vehicle if accompanied by the holder of a Class "A" driver's license;
(h) The Class “B” Commercial Driver’s Instruction License Endorsement is required with a Class “C” or Class “D” driver’s license to permit the licensee to operate a Class “B” vehicle if accompanied by the holder of a Class “A” or Class “B” driver’s license; and
(i) The Class “C” Commercial Driver’s Instruction License Endorsement is required with a Class “D” driver’s license to permit the licensee to operate a Class “C” vehicle if accompanied by the holder of a Class “A,” Class “B” or Class “C” driver’s license.
1313.2 The following chart shows the symbols to be used for endorsements that shall appear on the driver’s license to authorize driving of the following:
1313.3 The following restrictions shall be displayed on a driver’s license to specify special conditions under which a driver may operate a motor vehicle:
(e) May not operate Class “A,” “B” or “C” vehicles in interstate commerce;
(f) Valid only when presented with official document noting special driving conditions; and
(g) Valid only when presented with a valid medical card; and
(h) May not operate tractors and semi-trailers.
1313.4 The Director, or his or her designee, may modify the endorsements and restrictions in § 1313 when deemed necessary to implement this chapter.
SOURCE: Final Rulemaking published at 51 DCR 10913 (November 26, 2004); as amended by Final Rulemaking published at 52 DCR 4023 (April 22, 2005); as amended by Final Rulemaking published at 60 DCR 10071 (July 12, 2013).