Bumpy economy cited as helping improve U.S. roads

* Fewer motorists translates to less wear and tear

* Improvements also reflect increased highway spending

* California ranks worst for urban freeway gridlock

By Steve Gorman

LOS ANGELES, Sept 2 (Reuters) - One upside of the worst U.S. economic slump since the Great Depression is that with fewer motorists on the road, the nation's highways are less congested and in better shape, a study said on Thursday.

The condition of urban interstate highways and rural primary roads both showed significant gains in 2008, the latest year for which complete figures were available, according to the Reason Foundation, a Los Angeles-based think tank.

Urban interstates and rural primary roads, accounting for most of the 140,000 highway miles (225,000 km) covered in the group's 19th annual highway report, also were found to be in their best condition since 1993.

Moreover, urban interstate congestion and the rate of highway deaths per miles driven continued to decline, mirroring trends for improved road and bridge conditions during recent years, the study found.

Much of the improvement reflects increased spending on state-administered roads, which has nearly tripled since 1984 and jumped 8 percent from 2007 to 2008 alone.