A study by the national Brookings Institution said the state of Missouri should stop building highways that the think tank contends contribute to sprawl - an effect caused when the expansion of suburbs into rural areas creates lower density cities.

The study said many of Missouri's problems, including the state's well-documented difficulties raising money for transportation, were linked to the way the state's cities have sprawled into a more decentralized style of development.

"Missouri's current pattern of growth is straining the state's transportation system and burdening Missourians with increasing travel costs," the study said. "Most notably, the widening area that needs to be served by high-capacity roads has increased the costs of building and maintaining an adequate highway network.

"Rectifying the state's current maintenance backlog will require up to $645 million a year over the next 10 years," the study said, "some $242 million more than current funding provides."

The study said the state should emphasize maintaining current roads, rather than building new ones.

"On the road front, MoDOT has begun the change," the study said. "Of late it has made 'taking care of what we have' its top priority, acknowledging that its past emphasis on building new roads instead of maintaining established ones resulted in a deteriorating system."

However, the study also suggested the state spend more on public transit and indicated the state should not spend fuel taxes solely on roads.

"In Missouri, as in many states, transportation policy has focused on highway and road expansion to the exclusion of alternative strategies," the study said. "Currently, the state invests only small sums in the state's 250 urban and rural transit systems, while a constitutional requirement mandates that gas-tax revenues be spent exclusively on roads and bridges.

"Such priorities keep the state from developing a truly balanced transportation system that will help build livable, convenient communities."