In the United States, amber front and red rear side marker lamps and retroreflectors are required. The law initially required lights or retroreflectors on vehicles manufactured after 1 January 1968. This was amended to require lights and retroreflectors on vehicles manufactured after 1 January 1970. These side-facing devices make the vehicle's presence, position and direction of travel clearly visible from oblique angles.
The lights are wired so as to illuminate whenever the vehicles' parking and taillamps are on, including when the headlamps are being used. Front amber side markers in the United States may be wired so as to flash in synchronous phase or opposite-phase with the turn signals; nevertheless, they are not required to flash at all. Side markers are permitted but not required on cars and light passenger vehicles outside the United States and Canada.
If installed, they are required to be brighter and visible through a larger horizontal angle than US side markers, may flash only in synchronous phase with the turn signals (but are not required to flash), and they must be amber at the front and rear, except rear side markers may be red if they are grouped, combined, or reciprocally incorporated with another rear lighting function that is required to be red.
Japan's accession to international standards has caused automakers to change the rear side marker colour from red to amber on their models so equipped in the Japanese market.