The paper examines the role that the condition of the windshield plays in night-time accidents. It draws attention to the fact that windshields are subject to wear during the life of the car. An instrument is presented, the stray light analyzer, which measures the stray light caused by these defects. Field test show that badly worn windshields reduce the distance at which objects on the road can be seen by the driver. A procedure to collect data on night-time accidents is proposed that may allow an estimate of the percentage of night-time accidents that could be avoided by keeping windshields clean and the benefits in terms of saved lives that can be gained by replacing windshields when they reach a certain amount of wear.