If you are driving a motor vehicle that is towing a trailer or a camp trailer, the entire setup must have a lamp-based turn signal system.

This law states that vehicles can have turn signals to indicate turns. However, certain vehicles must have these signals: Motortrucks, truck tractors, buses, and passenger vehicles (except motorcycles) made and registered after January 1, 1958; trailers and semitrailers over 6,000 pounds registered between December 31, 1957, and January 1, 1969; trailers and semitrailers over 80 inches wide made after January 1, 1969; and motorcycles manufactured and registered after January 1, 1973, except slower motor-driven cycles. Special mobile equipment and auxiliary dollies don't need turn signals. Turn signals on vehicles made after January 1, 1969, must be at least 15 inches off the ground.

This law requires that turn signal lights on vehicles must be easily seen and understood from a distance of at least 300 feet in both daylight and nighttime. However, for larger vehicles that need clearance lamps, the turn signals must be visible from 500 feet.

This California law covers the requirements for vehicle turn signal lights. It states that turn signals must show a flashing white or amber light at the front and a flashing red or amber light at the rear. Side-mounted turn signal lights can emit flashing amber light sideways, and if they are located to the rear of the vehicle's center, they can show a red light that is not visible from the front.

Supplemental rear turn signals can also be added to the back of the driver's seat or integrated into the car's rearview mirrors, provided they flash with the rear signals and aren't visible to the driver except for monitoring purposes. These extra lights must only emit light to the rear without being glaring.