Lane departure warnings, blind spot detection have major effect on reducing crashes

New vehicle technologies have been having a significant effect on preventing crashes in the United States, according to a recent pair of studies by the Insurance Institute for Highway Safety. Researchers determined that lane departure warnings and blind spot detection have been particularly effective.

When controlling for demographic factors such as age, gender, and insurance risk level, lane departure warnings were found to reduce crashes by 11 percent and crashes with injuries by 21 percent. Blind spot detection cut lane change crashes by 14 percent, with a 23 percent reduction in lane change crashes with injuries.

Lane departure warnings

Lane departure warnings give an audible signal, and sometimes nudge a vehicle back into the correct roadway markings, if the vehicle starts to drift out of the lane. The system is designed to prevent vehicles from running off the road or colliding head-on with an oncoming vehicle, which often results in fatalities.

The IIHS study on this technology looked at police data on single vehicle, sideswipe, and head-on crashes in 25 states between 2009 and 2015. The number of crashes involving vehicles with lane departure warning technology was compared to the expected number of crashes based on crash data related to the same vehicle type without a lane departure warning system.

IIHS determined that lane departure warnings lowered the rate of the crashes it is designed to address by 11 percent when controlling for demographic factors and 18 percent without this control. It also cut crashes with injuries by 21 percent with the control and 24 percent without it. The study concluded that if all passenger vehicles had been equipped with the technology in 2015, it would have resulted in 85,000 fewer police-reported crashes and 55,000 fewer injuries.

"This is the first evidence that lane departure warning is working to prevent crashes of passenger vehicles on U.S. roads," said Jessica Cicchino, IIHS vice president for research. "Given the large number of fatal crashes that involve unintentional lane departures, technology aimed at preventing them has the potential to save a lot of lives."

The data available did not include enough fatal crashes to make a statistical model to control for demographic factors. However, a simpler analysis suggested that lane departure warning systems reduced the fatality rate in head-on, sideswipe, and single vehicle crashes by 86 percent.

The reduction in less severe crashes is not as pronounced as in other studies on the effectiveness of lane departure warnings. A 2015 study determined that the technology cut relevant crashes by half among U.S. truck fleets, while an analysis of Volvo vehicles in Sweden similarly concluded that it reduced relevant crashes with injuries by 53 percent.

IIHS suggests that the smaller reduction in crashes shown in the latest study may be a result of drivers opting not to use the lane departure warning on their vehicle. A separate study by the institute, released in June, looked at 983 vehicles that had been brought in for servicing and found that nearly half of them had their lane departure warning systems turned off. IIHS said that many drivers opted to deactivate the warnings because they found them to be annoying.

Many systems will only warn the driver that they are drifting out of their lane, after which they will need to take action to correct the issue. Another IIHS study, released in 2016, found that just over one-third of the drivers in 631 crashes where the vehicle had drifted out of the lane were asleep, experiencing a medical issue, or otherwise incapacitated.

Blind spot detection

The study on the effectiveness of blind spot detection systems used a method similar to the one used in the study of lane departure warning systems. Cicchino used data on police-reported crashes in 26 states for the years 2009 to 2015.

The IIHS analysis focused on crashes that occurred during a lane change or merge. Blind spot detection systems are designed to alert a driver if a vehicle is adjacent to them in their blind spot during these maneuvers.

When controlling for demographic factors, blind spot detection systems reduced lane changing and merging crashes by 14 percent. The technology was also found to cut these types of crashes with injuries by 23 percent, although this result was not statistically significant.

"Blind spot detection systems work by providing additional information to the driver. It's still up to the driver to pay attention to that information and use it to make decisions," said Cicchino. "That said, if every passenger vehicle on the road were equipped with blind spot detection as effective as the systems we studied, about 50,000 police-reported crashes a year could be prevented."


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