Enforcement is sporadic

The enforcement of failure-to-signal violations varies by state, and most police departments do not track or publish statistics on how many tickets are written each year.

For example, California law requires drivers to use a turn signal 100 feet before an intersection. But according to Lt. David Gilmore of the San Diego County Sheriff's Department, that limit is rarely enforced.

In many jurisdictions a failure-to-signal citation is written only if an improper turn results in an accident.

Instead, failure to signal is often a handy tool for police to establish a valid reason to pull over a vehicle that they think is suspicious. A signal violation is a primary offense -- one that legally allows a traffic stop. Police might suspect a driver is drunk, transporting drugs or guilty of any number of other infractions.

That practice can be controversial.

Florida attorney Shane Fischer says that in his experience, failure-to-signal tickets are much more common in poor, predominantly African-American or Latino communities.

Data presented in Chavez v. Illinois State Police, a class-action lawsuit, showed that Hispanics, while less than 3% of the driving-age population in one district, made up 25% of drivers pulled over in discretionary stops for offenses such as failure to signal a lane change.

A brief history of the turn signal

Before blinkers became common, drivers were required to roll down their window and stick an arm out, rain or shine, to signal their direction or a stop.

In Europe, a mechanical device known as a "trafficator," or semaphore, was used into the 1920s; mechanical arms swung out from the car's windshield pillars or doors to indicate direction.

Buick was the first automaker to offer factory-installed turn signals. Its 1939 models featured the "Flash-Way Directional Signal" only on the rear lights. The 1940 models added front indicators and a self-canceling mechanism.

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In the seven decades since, the technology hasn't changed much. Turn signals became standard equipment on most cars during the 1960s. In 1968, the federal government required that front turn signals have an amber-colored lens while the rear could be either red or amber. Those standards still exist.

Ponziani's RLP Engineering group has proposed a "smart turn signal" that would flash a reminder if it senses turns that aren't accompanied by signals and automatically cancel a lane-change signal after a certain amount of time.

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