How many people have died in car crashes since 9/11? The US averages somewhere around 50,000 fatalities per year, so statistically we should be approaching the same number of deaths in the two months subsequent to 9/11 as were sustained in the terrorist acts.
Auto crash fatalities tend to happen one or two at a time in geographically diverse areas, so we don't pay them much attention. Hearing about a death in a rush hour wreck just becomes part of the background noise on the evening news, or an item on page 5b of the local paper.
Bottom line - keep your head on a swivel out there regardless of how you travel. Be aware, be safe.