The insurance industry has focused safety research efforts almost exclusively on speeding and distracted driving. Only one study, published by SAE International in 2012, looked at collecting objective data on the use of turn signals under the assumption that failure to signal has a significant impact on accident rates. The 2012 study's author, Richard Ponziani of RLP Engineering, sells an automated turn signaling technology called Intelliturn.

"In contrast to pointing out that there is scant research on the subject of turn signal usage rates, it is important to highlight several prominent recent literature publications where turn signal usage rates would presumably be a focus of discussion, yet the subject is conspicuously absent," Ponziani wrote. "These NHTSA publications are not singled out in order to denigrate the work or findings of these publications, but to show how an important subject related to vehicle safety is just not on our collective consciousness as it relates to directing safety improvement efforts."

Ponziani points to a number of studies exploring the causes of intersection collisions and driver inattention that never mention turn signals over the course of more than a thousand pages of research. To remedy this, Ponziani sent out two people to drive around Dayton, Ohio and record turn signal usage. One observer was responsible for keeping a tally of turns signals being used, the second was to record each time a signal was not used. A total of 12,000 vehicles were recorded turning or changing lanes at night and during the day during medium traffic conditions.

The study found signals were properly used for turns 75 percent of the time and were ignored in the remaining 25 percent of cases. Drivers were much more likely to ignore turn signals when changing lanes, as the usage rate was found to be just 51 percent.

"We currently have turn signals installed on all vehicles and there are turn signal usage laws, but enforcement of these laws is not consistent and in fact largely ignored by law enforcement," Ponziani wrote. "A turn signal used properly raises active safety to another level and not only serves to prevent crashes, but prevents near-crash situations and enhances the flow of traffic."

Not surprisingly, the study recommends the use of dashboard nag systems to remind drivers to use their signal as well as the "smart" turn signal technologies that the study's author sells. Copy of the report is available in a 500k PDF file at the source link below.