A Brief History of Turn Signals

Q: Too often I see drivers give maybe one blink of their turn signal before turning. That can’t be enough to meet the requirements of the law, right? How far in advance of an intersection or lane change are you required to activate your turn signal?

A: Our turn signal law is imperfect. Why? Maybe because we don’t like math. To see how I reached that conclusion, let’s dig into the history of turn signals and Washington’s turn signal laws.

Karl Benz gets credit for inventing the car in 1886. Success has many fathers, and there were folks before Benz building car-like vehicles, but we like heroes and had to pick someone. The first patent for a turn signal device (this one mechanical) was filed in 1907. In the years following, several other turn signal ideas were invented and forgotten.

A hundred years ago, turn signals were still an experiment, and 1927’s session laws suggests that maybe too many drivers were experimenting. The law prohibited drivers from using mechanical or electric devices as a substitute for hand signals, unless the device had been approved.

The 1932 Talbot 105 was, as far as I can tell, the first car that came with factory installed turn signals. Only 330 were sold to the public. The 1939 Buick gets credit for being the first car to come with turn signals, because no one remembers the Talbot car company.

In 1937 Washington overhauled its traffic laws, which included a section on using turn signals. The law required drivers to signal “continuously for a reasonable length of time,” and defined reasonable as the time it takes to travel a distance in feet equal to five times the speed limit in miles per hour. If the posted speed limit is 25 mph, you’d have to signal for at least 125 feet. The law forced drivers to do math, and you couldn’t count on your fingers. Electric turn signals were rare, so your hands were busy signaling.

The 1953 session law required that all vehicles manufactured after January 1, 1954 be equipped with turn signals. It also updated the minimum distance for signaling, requiring drivers to signal 100 feet before turning or use the five times rule mentioned above. I’m not sure how to interpret that. Was the 100-foot requirement a minimum no matter what the speed limit? If so, it would only apply to speeds below 20 mph, which is almost nowhere. Can drivers choose one option over the other? If so, that would make the five times rule pointless because it’s almost always going to be longer than 100 feet.

My puzzlement is moot, though, as the law eventually dropped the five times rule. It now only requires signaling 100 feet before turning (and I consider that a loss). With the five times rule, no matter the speed limit you’ll always be signaling for about 3.5 seconds. That doesn’t seem like much, but consider this; at 70 mph you travel 102 feet in one second. Turn signals blink at a rate of 60 – 120 flashes per minute so, if a car’s turn signal is on the low end of that, at 70 mph you’d only get one blink in 100 feet. That complies with the law, but it’s not too helpful to other drivers.

At most speeds our turn signal requirements are insufficient. It’s an example of the law setting bare minimums, while good drivers know that safe driving requires a higher standard. We have limited tools for communicating with other drivers, so we should make the best of them and give more than one blink.