North Dakota does the best job maintaining its roads and bridges, but across the country, 24.1 percent of bridges are deficient or functionally obsolete, according to an annual study that measures each state's road conditions and expenditures.

The Reason Foundation's 17th Annual Report on the Performance of State Highway Systems, released July 31, found that New Jersey has the worst-performing, least cost-effective highway system in the nation.

Massachusetts' roads are the safest; Montana's are the deadliest, according to the study.  In Rhode Island, over 53 percent of bridges are deficient.

At our current rate of repair it will take 62 years for today's deficient bridges to be brought up to date, according to the study.  California has the most traffic congestion, with 83 percent of its urban interstates congested. But 18 states report at least half of their urban interstates are jammed.

The study measures the condition of all state-owned roads and highways from 1984 to 2006.  It calculates the effectiveness and performance of each state in categories such as pavement condition, bridge condition, traffic fatalities, congestion, highway maintenance costs, and administrative costs. 

California ranked 44th in the overall state highway performance and cost-effectiveness ratings, the same as last year. California has the highest percent urban interstate congested in the entire nation, 83.3 percent.