It is not recommended to drive with a crack in the windshield, according to cars.com. Even a small crack or chip can form into larger cracks, which can affect driver visibility. Cracks over 12 inches long can also result in driving violations or tickets.
If a driver must drive with a small crack prior to repair, using the defroster or air conditioning should be avoided. Extreme changes in temperature can cause more cracks or bigger cracks in an already compromised windshield. Suddenly jolting the car or slamming doors can also result in more severe cracking. Cracks over 12 inches long usually require the replacement of the entire windshield.