Lane departure prevention systems that wait too long to initiate steering input or fail to prevent lane drifts greater than 35 centimeters may cause drivers to deactivate them, according to a new study from the Insurance Institute of Highway Safety.

The study results indicate that early intervention via slight nudges from the steering wheel and subtle braking as soon as tires start to drift could be key to increasing use of this crash avoidance technology.

IIHS evaluated lane departure prevention systems from Ford, General Motors, Honda, and Volvo to assess where steering or braking occurred relative to lane markings, and whether the efforts successfully kept the vehicles in their travel lanes.

Tests were conducted at 50 mph with cruise control engaged on a four-lane highway. Test vehicles included three 2016 models, specifically, Chevrolet Malibu with Lane Keep Assist, Ford Fusion with Lane Keeping System, and Honda Accord with Road Departure Mitigation. A 2018 Volvo S90 with Lane Keeping also underwent testing.

Test drivers induced 40 lane drifts on left and right curves by steering their respective vehicles straight into the curve so that vehicles departed in the opposite direction and 40 lane drifts on straightaways by slight steering input to direct the vehicle to the left and right lane markers.

With the use of outboard cameras and video, researchers determined whether a vehicle crossed lane markers by more than 35 centimeters (about 14 inches) on any of its trials.

Both the Malibu and S90 systems provided steering input further inside the lane than the Accord and Fusion, and they produced the lowest mean peak changes in the yaw rate. On both curves and straightaways, the Malibu and S90 avoided a much larger proportion of lane marker crossings exceeding 35 centimeters than the Accord and Fusion.

The S90 avoided crossing the inside edge of solid lane markers by more than 35 centimeters on 100 percent of the trials, and the Malibu avoided doing so on 80% of the trials. In contrast, the Accord and Fusion avoided crossing lane markers by more than 35 centimeters in less than 20% of the trials.

IIHS concludes that intervention that comes sooner rather than later may allow for more subtle input that keeps the vehicle in its lane. In addition, it may prompt drivers to consistently use the lane departure prevention system.