A three-lamp signal head showing red, amber and green in a fixed vertical order.
Also known as: Traffic signal, Stoplight, Three coloured lights
The traffic signal's three lamps sit in a fixed order — red at the top — so that a driver who cannot distinguish the colours can still read the signal by position. That ordering is the sign's most important design decision and is prescribed rather than conventional.
Uses red to require stopping, green to permit proceeding, and amber to signal that the change to red is imminent.
Contracting parties to the 1968 Vienna Convention · Contexts: Road signage
Places the lamps in a fixed order with red at the top of a vertical head, so that the signal remains readable by position to a driver who cannot distinguish red from green.
Contracting parties to the 1968 Vienna Convention · Contexts: Road signage
Derives from railway signalling practice, from which road traffic borrowed both the colour scheme and the idea of a fixed lamp order.
Contexts: Road signage
A tall dark rectangular housing containing three circular lamps stacked vertically: red at the top, amber in the middle and green at the bottom.
A signal-controlled crossing combines the two.