Highways in the US state of California are in the best shape they have been in for nearly 19 years, according to the 19th annual highway report by the Los Angeles-based Reason Foundation.

The study measures the condition of state highways in 11 key categories, including deficient bridges, urban traffic congestion, fatality rates and pavement condition.

The study says national performance of roads and bridges in the key areas improved in 2008.

Overall, North Dakota, Montana and Kansas have the most cost-effective state highway systems while Rhode Island, Alaska, California, Hawaii and New York have the least cost-effective roads.

Massachusetts has the safest roads with 0.67 fatalities per 100 million miles driven, while Montana and Louisiana have the highest fatality rates at 2.12 and 2.02 fatalities per million miles driven.

The study credits increased spending from states and the reduction in vehicle miles travelled during the recession as some of the factors for improvement in highway conditions.