Most race cars don't have glass windows — they add weight, and you don't want shattered glass everywhere after a collision. (If this article is proving anything, it should be that collisions are going to happen). Prior to 1970 stock cars were windowless, with an opening where the glass would be in a road car. In NASCAR cars today, those openings are covered with safety nets. Drivers can thank Richard Petty for that.
At the 1970 Rebel 400 in Darlington, South Carolina, Petty drove a Plymouth Road Runner, although he usually drove a Plymouth Superbird (the Superbird, alas, had been wrecked in practice). His steering failed in lap 176 of the race, sending the car into the outside wall then back toward the pit wall. The car then rolled five times before stopping. Petty's arm and shoulder ended up outside the car and were terribly injured [source: Pearce]. While Petty survived and raced for many more years, this crash led to the addition of safety netting, which has saved other drivers from similar injuries or worse.