Veh. Code, § 24600

During darkness every motor vehicle which is not in combination with any other vehicle and every vehicle at the end of a combination of vehicles shall be equipped with lighted taillamps mounted on the rear as follows:

(a) Every vehicle shall be equipped with one or more taillamps.

(b) Every vehicle, other than a motorcycle, manufactured and first registered on or after January 1, 1958, shall be equipped with not less than two taillamps, except that trailers and semitrailers manufactured after July 23, 1973, which are less than 30 inches wide, may be equipped with one taillamp which shall be mounted at or near the vertical centerline of the vehicles. If a vehicle is equipped with two taillamps, they shall be mounted as specified in subdivision (d).

(c) Every vehicle or vehicle at the end of a combination of vehicles, subject to subdivision (a) of Section 22406 shall be equipped with not less than two taillamps.

(d) When two taillamps are required, at least one shall be mounted at the left and one at the right side respectively at the same level.

(e) Taillamps shall be red in color and shall be plainly visible from all distances within 500 feet to the rear except that taillamps on vehicles manufactured after January 1, 1969, shall be plainly visible from all distances within 1,000 feet to the rear.

(f) Taillamps on vehicles manufactured on or after January 1, 1969, shall be mounted not lower than 15 inches nor higher than 72 inches, except that a tow truck, in addition to being equipped with the required taillamps, may also be equipped with two taillamps which may be mounted not lower than 15 inches nor higher than the maximum allowable vehicle height and as far forward as the rearmost portion of the driver’s seat in the rearmost position. The additional taillamps on a tow truck shall be lighted whenever the headlamps are lighted.