Nighttime visibility is critical to highway safety. About half of traffic deaths occur either in the dark or at dawn or dusk.

Few vehicles have headlights that do their job well. IIHS evaluations show that the on-road illumination provided by vehicle lights varies widely.

Some new types of lighting technology show promise. High-beam assist increases high-beam use by automatically switching between high beams and low beams, depending on whether other vehicles are present. Curve-adaptive headlights pivot in the direction of travel to improve visibility on curvy roads.

Good headlights shouldn't cause excessive glare. Properly aimed low beams light up the road ahead without temporarily blinding drivers of oncoming vehicles. IIHS headlight ratings take glare into account.

How headlights compare

IIHS vehicle ratings include the results of our headlight evaluations, which measure the reach of a vehicle's headlights as it travels straight and on curves.