New data released today from the Texas Transportation Institute. http://mobility.tamu.edu/ums/congestion_data/tables/national/table_4.pdf
According to the report, the average L.A. metro commuter spends an extra 70 hours per year sitting in traffic delays -- that's 2 whole work weeks. And it's up from 44 hours per week in 1982.
According to a TSTC analysis at http://blog.tstc.org/2009/07/08/traffic-congestion-solved-if-only/ , congestion in the NYC area is very costly to the local economy:
"Even so, commuters in New York City still spent more than a typical work week (44 hours) stuck in traffic on an annual per capita basis. In Philadelphia, the figure was 38 hours. TTI calculates that Stamford-Bridgeport commuters spent 33 hours in traffic. In Hartford and New Haven, commuters spent 21 and 19 hours in traffic respectively. The cost of wasting all that time in traffic (in extra fuel and lost productivity) amounted to an astounding $11.2 billion annually for the entire tri-state region."