Transportation Secretary Mary Peters said the decline in driving will mean less money for the highway repairs and construction projects needed to relieve traffic congestion. The Highway Trust Fund, which underwrites the projects, is funded by the federal 18.4-cents-a-gallon tax on gasoline and 24.4-cents-a-gallon tax on diesel. Utah's tax is 24 cents a gallon on gasoline.

"We can't afford to continue pinning our transportation network's future to the gas tax," Peters said. "Advances in higher-fuel-efficiency vehicles and alternative fuels are making the gas tax an even less sustainable support for funding roads, bridges and transit systems."

A study released Wednesday by the Utah Foundation showed transportation is nudging upward as a priority for Utah voters, ranking ninth this year compared to ranking 11th in the foundation's 2004 study.

Transportation topics that voters identified as most important include travel times, the quality of roads, development of public transportation and expanding the capacity of freeways and interstates in Utah.

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Contributing: The Associated Press

E-mail: cnorlen@desnews.com