The Obama $800 billion stimulus package could stimulate headaches for environmentalists and smart growth advocates who fear that the urgency to create jobs will spur suburban sprawl — by building new roads, rather than mass transit.

“Our biggest concern is that in the haste to get money out the door for so-called ready-to-go projects, we will fund some highways to nowhere that have been lying around in the planning stages in some states,” says David Goldberg, communications director for Transportation for America, a coalition of reform-minded housing, environmental, public health, urban planning, and transportation groups.

While Obama promises pork-free, green stimulus projects, reality dictates there will be conflicts between jobs now and good planning, which can take a decade or more for mass transit, adds Robert Dunphy, a senior fellow at the Urban Land Institute in Washington. There are mass transportation projects ready to move, he says, such as adding buses to crowded urban routes and improving aging subway systems. But smart-growth advocates fear that Congress will listen solely to transportation officials, whose wish list is heavy on highway projects in rural areas, and who are pushing for no-strings-attached provisions that could benefit powerful industries.

Highway construction advocates now lobbying Congress argue that they, in fact, represent a green interest. “The U.S. Department of Transportation has a list of over 400 congestion points on highways around the country,” says Clayton Boyce, spokesman for the American Trucking Associations. “If you fix any of those congestion points you will make reductions in fuel consumption and carbon output.”

In rural areas, some officials fear that stimulus funds will open the door to unwanted development on far-flung agricultural lands. Bucks County, Pennsylvania, township supervisor Henry Rowan worries that the influx of money will pay for additional municipal water and sewer capacity, which would allow developers to build on farmland that now requires wells and septic systems. Deron Lovaas of the Natural Resources Defense Council remains optimistic that Congress will strike a balanced approach. Still, he worries. “The easiest thing to do,” he says, “is to invest in the existing system.”