trafficator
A blinking light on a motor vehicle that indicates the direction in which it is about to turn.
trafficator: the arm-mounted turn signal that came before the light
A trafficator is a mechanical signaling arm that pivots outward from the side of a motor vehicle to indicate turning intent. Popular from the 1920s through the 1950s, it combines a physical semaphore arm, usually yellow or amber, with an internal light that flashes or glows when extended. The arm retracts flush against the vehicle body when not in use.
The device mounts typically above the front door or on the B-pillar, actuated by a dashboard lever or, later, a steering column stalk. When the driver moves the control, a solenoid or mechanical linkage extends the arm outward perpendicular to the vehicle's side. The arm remains extended until the driver manually retracts it or (on some models) until a timer mechanism resets it automatically after the turn is complete.
Two design variants dominated the market. The semaphore trafficator used a flat metal arm that swung 90 degrees and remained visible in daylight. The light trafficator added an amber bulb inside the arm itself or mounted an illuminated lens alongside it, making the signal visible at night. Both types relied entirely on driver visibility and action; there was no synchronization with the ignition system or automatic cancellation.
Why they fell from favor
Trafficators became obsolete after the 1950s because electric turn signal lights (flashing or steady) proved more reliable, required less maintenance, and could be integrated into the vehicle's electrical architecture more easily. They also failed in heavy rain, snow, or when obscured by luggage, and a broken arm left no backup signal. Modern regulations worldwide now mandate electric amber or red lamps for turning; semaphore arms survive only on classic or vintage vehicles.
The name derives from the Latin trafficare (to trade or traffic) merged with indicator, though the term is primarily British and European. North American drivers typically used the term turn signal or direction signal from the start of electric signaling. Some jurisdictions, particularly the UK, continued manufacturing and installing trafficators well into the 1960s on lower-cost vehicles, even as higher-end models switched to electric lights.