The True Costs of Driving
(some of them, at least)

$160 billion is spent annually by all levels of government on highway construction, maintenance and operations. Approximately 60% is covered by user fees. (2004 data; 2006 data)

Traffic crashes cost the nation between $164 billion (in urban areas, AAA, 2008) and $230 billion (NHTSA, 2000) annually. 43,000 people are killed in crashes; 2.6 million are injured.

Congestion in metropolitan areas costs $78 billion annually.

Between 40,000 and 70,000 premature deaths due to poor air quality at a cost of up to $64 billion annually

$75 billion in direct medical costs due to physical inactivity (CDC, 2003 figures)

Cost of free parking to the national economy: $300 billion. Cost of one surface parking space is $10,000; parking garage spaces between $20,000 and $40,000.

Good summaries of the external costs of driving are provided by Delucchi and Litman.

Another interesting number for comparison:

Car advertising topped $18 billion in 2007 – the hard-hit automotive industry was knocked into second place for the largest U.S. ad-spending category, after the retail sector.