Get dirt on the windshield

For example, when you are driving behind driver who puts his tires out of the track and rises a dust cloud.

http://img834.imageshack.us/img834/1601/lnqw.jpg

Obviously the same with the rain spray.

 

+1. I don´t mind in something scripted during races. In street cars this should be clean on pit stops and in modern open wheels we could assign a button in control setting to remove layers from the visor mod to get cleaner vision during races.