D.C. Mun. Regs. tit. 18 § 2200
Except when a special hazard exists that requires lower speed for compliance with this section, the limits specified in this section, or established as authorized in § 2200.2, shall be the maximum lawful speeds, and no person shall drive a vehicle on a street or highway at a speed in excess of such maximum limits.
Whenever the Mayor determines, upon the basis of an engineering and traffic investigation made by the Director, that any speed limit set forth in this section is greater or less than is reasonable or safe under the conditions found to exist at any intersection or other place or upon any part of a street or highway, he or she may determine and declare a reasonable and safe speed limit which shall be effective at all times, during the hours of daylight or darkness, or at such other times as may be determined when appropriate signs giving notice of the speed limits are erected at such intersections or other place or part of the highway.
No person shall drive a vehicle on a street or highway at a speed greater than is reasonable and prudent under the conditions and having regard to the actual and potential hazards then existing.
In every event speed shall be so controlled as may be necessary to avoid colliding with any person, vehicle, or other conveyance on or entering the street or highway in compliance with legal requirements and the duty of all persons to use due care.
The driver of every vehicle shall, consistent with requirements of this section, drive at an appropriate reduced speed when approaching and crossing an intersection or railway grade crossing; when approaching and going around a curve; when approaching a hill crest; when traveling upon any narrow or winding roadway; and when special hazard exists with respect to pedestrians or other traffic, or by reason of weather or highway conditions.
On all streets and highways, unless otherwise designated in accordance with § 2200.2, the maximum lawful speed shall be twenty miles per hour (20 mph).
In all alleys, the maximum lawful speed shall be fifteen miles per hour (15 mph).
On roadways adjacent to school facilities and grounds serving youth, the maximum lawful speed shall be fifteen miles per hour (15 mph) when designated by an official sign at the times indicated on the official sign.
On roadways adjacent to a playground, recreational facility, health care facility, pool, athletic field, or senior center designated by official signs, the maximum lawful speed shall be fifteen miles per hour (15 mph) when designated by an official sign at the times indicated on the official sign.
No person shall drive a motor vehicle at such a slow speed as to impede or block the normal and reasonable movement of traffic, except when reduced speed is necessary for safe operation or to be in compliance with the law.
Any individual violating any provision of this section, except where the offense constitutes reckless driving or a specific penalty is provided for the offense, shall, upon determination of liability therefor, be subject to a civil fine pursuant to the District of Columbia Traffic Adjudication Act.
Any individual who shall drive a vehicle on a roadway or highway at a speed greater than thirty miles per hour (30 mph) in excess of the legal speed limit for such roadway or highway shall, upon conviction, be fined not more than the amount set forth in the Criminal Fine Proportionality Amendment Act of 2012, effective June 11, 2013 (D.C. Law 19-317; D.C. Official Code § 22-3571.01 ), or imprisoned not more than ninety (90) days, or both, provided that if the vehicle is detected through the use of an automated traffic enforcement system of traveling at a speed greater than thirty miles per hour (30 mph) in excess of the legal speed limit, the owner shall be liable for the fine established in Section 2600 of this title.
D.C. Mun. Regs. Tit. 18, § 2200