ATLANTA — Commuters battling traffic in the Bay Area or New York might protest, but Atlanta-area traffic seems to be uniquely awful.

For more than a decade, Atlanta has been among the fastest-growing regions in the country, but the road and rail system in a state that ranks 49th in transportation spending per capita just could not keep up.

Hourlong commutes are common, and more than 80 percent of commuters drive alone. Only 5 percent make use of the region's limited train and bus systems, according to research by the Brookings Institution.

This month, Atlanta-area voters are being asked to approve an ambitious fix that would ultimately raise $8.5 billion by adding a penny to the sales tax for 10 years.

The proposal, which bundles 157 projects in 10 counties, is part of a July 31 referendum that will allow voters across the state to decide if they want a new tax for transportation specific to their region. Voters in the Savannah area, for example, will decide on a $229 million package of road and transit improvements.

The complex regional voting scheme could bring in more than $18 billion in new tax money, plus additional federal money, making it one of the largest packages of its kind in the country, transportation experts said.

"A lot of states are looking at it very carefully to see what happens because it's a politically safe way to get transportation funding," said Brent Buice, executive director of Georgia Bikes!

"Essentially, this is a way to make people tax themselves." "It's a way for the Georgia Legislature to kick the can down the road and not have to raise the gas tax, which should have been raised a long time ago," said Buice, who will be voting for a package of projects in the Athens area.

Taxes to improve roads, telecommunications, sewers and other services are a tough sell these days. But the Georgia package is different.

"They are being very specific, and by doing so, they are vastly improving the likelihood of a positive vote," said Ken Orski, editor of Innovation NewsBriefs, a transportation newsletter.

In each of the 12 voting regions, 75 to 85 percent of the money would go to projects on an unchangeable master list. The remaining money would be given to cities and counties to spend on any transportation needs they might have in the future.

The legislature is pushing people to vote for the tax with a kind of carrot-and-stick incentive. Regions that do not support it will have to pay a bigger share to get state-supported road projects completed and may not get them done as quickly.

In Atlanta, which has by far the largest package, polls indicate that the vote will be close despite a vigorous campaign. Nearly $6 million has been spent on educational efforts, including a series of billboards along congested interstates with the slogan "Untie Atlanta."

The campaign has pulled together a quirky and powerful mix of advocates, led by Mayor Kasim Reed, who has made it the centerpiece of his agenda.

Hundreds of companies, from Coca-Cola and the Weather Channel to the Cook's Warehouse, a local kitchen shop, have pledged support, saying the region's transportation hurts business and arguing that the new projects would create jobs. Public transit and bicycling advocates like the proposal because 52 percent of the money would be dedicated to public transit.

Although little would be done to improve the beleaguered train system and less than 1 percent would go to bike and pedestrian projects, the money would bring a light-rail train for people who work near Emory University and the Centers for Disease Control and Prevention.

And it would be a big step for the city's BeltLine project, which aims to revitalize a 22-mile stretch of rail and green space that loops around Atlanta and could one day connect nearly every neighborhood in the city.

Even professional sports teams like the Atlanta Braves have come out in support, hoping that bad traffic — often cited as a reason for low attendance at games — would be eased.

But the vote also underscores the longstanding cultural and political rifts between the city and the region's vast suburbs, where critics contend the package is too heavy on public transportation and Atlanta-only projects.

Some opponents include some members of the NAACP, who argue that too few of the projects would help poor, largely black parts of the region, and the Georgia chapter of the Sierra Club, which says the project list puts too much emphasis on roads.

The Georgia Tea Party Patriots have been battling the proposal, calling it "the largest single tax increase in Georgia history" and contending it is full of special-interest projects and based on faulty assumptions about how traffic can best be fixed.