Failing to indicate causes 'millions of crashes per year', according to a Society of Automotive Engineers (SAE) report.
The US-based study shows that the effects of failing to indicate could be worse than 'distracted driving' - using a mobile phone behind the wheel.
The study watched 12,000 vehicles as they turned or changed lanes, and noted the rate of those who used their indicators. It showed that a staggering 48% of drivers didn't bother indicating when changing lanes, and 25% didn't when turning.
Scaled up, it means that US drivers fail to indicate 750 billion times per year, with "each incident of neglect [elevating] the risk of a multi-vehicle crash," according to the SAE.
The study says that "the collective result of turn signal neglect is as many as two million crashes per year" - more than twice the number of crashes that the US Department of Transport attributes to distracted driving.
The SAE, therefore, recommends that all cars adopt so-called Smart Turn Signal technology, which it describes thus:
The feature is similar to a seat belt reminder – if you habitually neglect the use of your turn signal when you execute turns, you will eventually get a friendly reminder display.
Smart Turn Signal technology uses the same sensors as the Stability Control System, which is standard on all new cars, which the SAE says makes it cost effective.
And it's not a bad idea, although some might suggest that improved driver training would be a more effective and responsible way of increasing indicator use.
"The turn signal is one of the very original automotive crash prevention devices and this simple driver to driver communication device remains extremely effective, but only when it is accurately displayed as required by law", said Richard Ponziani, who wrote the SAE report.