Adaptive headlights (ADHL) have been introduced by several car manufacturers as a technology to help the driver to better see in a curve in the dark. The headlights’ horizontal aim is directed where the vehicle is heading based on the speed of the vehicle and the direction of the steering wheel. Previous research has suggested that adaptive headlights have significant real-world benefits in reducing injury crashes with passenger cars. Headlight evaluation has also been included in car rating protocols. However, there are few effectiveness figures for specific crash types or situations. The objective of this study was therefore to investigate the real-world benefits of adaptive headlights in different crash types in Sweden.

Swedish police reported injury crashes involving Volvo cars (MY 2006-2015) were included in this study. The fitment of ADHL and other safety features was determined by consulting electronic parts catalogues with the VIN of each individual car.

In total, 1,303 ADHL-fitted cars and 5,262 cars without ADHL were identified. The statistical analysis used odds ratio calculations with an induced‐exposure approach. Daylight crashes were assumed to be non- sensitive for ADHL. The effectiveness of ADHL was estimated by calculating the odds ratios in darkness/daylight for single-vehicle crashes, crashes involving vulnerable road users as well as head-on and crashes at intersections.

ADHL were found to significantly reduce single-vehicle passenger car injury crashes in darkness by 39% (95% CI lower limit 11%). This is where the benefits of ADHL would be expected to become more evident, as the driver is assisted by the system through improved visibility. No significant reduction were found in other crash types. In two-vehicle crashes, ADHL may not be expected to provide significant benefits compared with conventional headlights.

As the proportion of single-vehicle crashes in darkness is rather limited in Sweden (3.5%), the overall benefits of ADHL were found to be 2%. Based on these findings, it may be doubtful that ADHL should be given great attention in rating schemes and assessment programs.