Los Angeles’ bumpy, pothole-ridden roads are among the costliest in the nation for drivers, said a study released Thursday by a national transportation research organization.

In its “Rough Ride Ahead” report, The Road Information Program said that L.A.’s roads cost drivers an additional $671 per year in wear and tear, above normal use. Only San Jose beat L.A., with its roads costing drivers an additional $689 per year, TRIP said.

The main reason for L.A. drivers’ added costs is the conditions of its major roads and highways. Nearly 64 percent of the roads in the Los Angeles metro area were rated “poor,” 27 percent “mediocre” and only 9 percent either “fair” or “good,” TRIP said.

Continued increases in urban traffic have caused significant wear and tear on the nation’s urban roads, TRIP said. Urban travel by large commercial trucks increased by 58 percent from 1990 to 2003, placing massive stress on road surfaces.

L.A. was No. 4 on among urban areas with the roughest roads in the country, beaten only by St. Louis (No. 3), San Jose (No. 2) and Kansas City (No. 1). The only other Southern California metro area among the top 10 was San Diego, which was No. 6.

TRIP is a non-profit organization that promotes transportation policies.