One traffic safety problem that has been observed in several studies is the wear of the windscreens. The risk of dazzling increases when driving with a worn windscreen, which may have the consequence that the driver does not discover objects or people on the road in front of the vehicle. The behaviour of 24 drivers has been studied in a driving simulator using three windscreens with different level of usage. To achieve dazzling in the driving simulator a lamp was mounted in front of the windscreen in the simulator. The lamp simulated a setting sun. When the driver had to make way for an obstacle on the road, this was more difficult with the worn windscreens, despite the lower speed. The drivers discovered the obstacles later, used a harder brake power and took a more powerful action to avoid the obstacle. Altogether this indicates a more risky driving behaviour, in other words decreased traffic safety. The sight length to a cone was also measured. The results showed that the sight length became shorter with worn windscreen. When the drivers were asked to express their opinion about the experiment, they assessed both the simulated environment and the driving task as relatively realistic. Even though this is a simulated situation, with its limitations, the results indicate that driving under dazzling conditions with a worn windscreen has negative effects on driver behaviour.