D.C. Code § 35-204
The Mayor of the District of Columbia is hereby authorized and empowered to make and to enforce all reasonable regulations in respect to requiring street cars operated by other means than horsepower in the District of Columbia to be provided with proper fenders for the protection of the lives and limbs of all persons within the District of Columbia. Such power and authority shall extend to the adoption by the said Mayor of any fender or fenders deemed by him to be superior to the fenders now in use as the fender or fenders which shall be used on cars operated within said District; provided, that nothing contained in this section shall operate to relieve any street-railway company from liability for accidents on its lines.
D.C. Code § 35-204