According to a Boston Globe article based on a national study commissioned by GMAC Insurance:
Many drivers have difficulty with such basic practices as merging and interpreting road signs. One out of five drivers does not know that a pedestrian in a crosswalk has the right of way. The study indicated that one out of three drivers speed up to make a yellow light, even when pedestrians are present. One out of 10 drivers regularly exceeds the speed limit by 11 or more miles per hour. One in three drivers said they would drink and drive as long as they felt “all right” to get behind the wheel.