Fossil fuel burning is the largest source of environmental mercury contamination in the environment. Many lakes in Northern Wisconsin have been killed by atmospheric deposition of mercury. Per passenger mile of travel, buses and rail contribute much less of every type of pollutant than cars. In the U.S. more people die from motor vehicle accidents than all other accidents combined. The death rate per passenger kilometer for cars is 97 times that for transit buses.
Noise levels can cause distress and hypertension.
Accidental oil spills are a daily occurrence and dump almost 3 million barrels of oil into the oceans annually. The rate and volume of runoff are both increased by increasing the amount of impervious surface in general. Traffic-related volume of pollutants are increased by converting land to road surface specifically. Urbanization increases the rate of runoff by 200 to 600 percent depending on the extent of urbanization. About 33.6 percent of the Madison area watersheds was impervious surface 15 years ago.