Turn signals
Turn signals — formally called directional indicators or directional signals, and informally known as “directionals”, “blinkers”, “indicators” or “flashers” — are signal lights mounted near the left and right front and rear corners of a vehicle, and sometimes on the sides, used to indicate to other drivers that the operator intends a lateral change of position (turn or lane change). Electric turn signal lights were devised as early as 1907. The modern turn signal was first generally offered by major automobile manufacturers in 1939.[citation needed] Today, turn signals are required on all vehicles that are driven on public roadways in most countries. Alternative systems of hand signals were used earlier, and they are still common for bicycles. Hand signals are also sometimes used when regular vehicle lights are malfunctioning.
Trafficator.
Some cars from the 1920s to 1950s used retractable semaphores called trafficators rather than flashing lights. They were commonly mounted high up behind the front doors and swung out horizontally. However, they were fragile and could be easily broken off and also had a tendency to stick in the closed position.
As with all vehicle lighting and signalling devices, turn signal lights must comply with technical standards that stipulate minimum and maximum permissible intensity levels, minimum horizontal and vertical angles of visibility, and minimum illuminated surface area to ensure that they are visible at all relevant angles, do not dazzle those who view them, and are suitably conspicuous in conditions ranging from full darkness to full direct sunlight.