Voters heading to the polls Tuesday will decide whether to amend the Missouri Constitution to approve the largest tax increase in Missouri history, a statewide sales tax to fund road improvements.

If voters approve Amendment 7, Missourians will pay a statewide three-quarter-cent sales tax to fund a projected $6.1 billion of road and infrastructure improvements on projects that will span the next decade.

The constitutional amendment was approved by the Missouri Legislature, and it was placed on the Aug. 5 ballot by Gov. Jay Nixon, who opposes the tax as regressive.

Although many legislators concede that a sales tax is not a perfect funding method for roads, alternatives to the sales tax — including a higher gas tax or toll roads — appear unlikely to gain support among either legislators or residents, which is why the Legislature chose the sales tax instead, said Rep. Marsha Haefner, R-Oakville.

“We’re not raising your taxes — you get to decide if you’re raising your taxes,” she said. “Now, if it doesn’t pass, I don’t know what we’re going to do, and we’re going to be faced with this problem (of fixing roads) again. If it does pass, I can assure you that this is a jobs bill, this is an economic development bill, because companies like to move to places that have good school systems and good transportation.”

For a gas tax to collect the same amount of money for roads as the sales tax, it would have to be at least 20 cents or more per gallon, Haefner added.

Nixon opposes the tax for its disproportionate impact on senior and low-income residents and chose to place it on the lower-turnout Aug. 5 ballot, noting, “If this effort is successful, Missouri will have the dubious distinction of being a state that, in a matter of months, cut taxes on lawyers and lobbyists, but hiked taxes on bar soap and baseball gloves.”

Missourians have formed coalitions across the state, both for and against Amendment 7. Labor and business interests have rallied around the tax with the expectation that it will create more jobs, with some groups projecting 100,000 jobs created. They have donated millions of dollars to pro-sales tax group Missourians for Safe Transportation and New Jobs to support the tax.

Grassroots group Missourians for Better Transportation Solutions opposes the tax on the grounds that it will give Missouri one of the highest sales taxes in the country — moving the state from 14th-highest sales taxes to seventh-highest sales taxes.

Some of the members of the anti-Amendment 7 coalition include the League of Women Voters, Sierra Club, NAACP and the St. Louis County Municipal League.

Trucking companies, which own the trucks that cause much of the damage to Missouri roads, are already exempt from paying sales taxes on new truck purchases and will not pay as much for the state’s roads as they would through a gas tax, said coalition members.

Locally, sales taxes in some areas in St. Louis County will climb above 10 percent, which will make the region unattractive to young families, said Republican county executive candidate Tony Pousosa, a Ward 1 Green Park alderman.

“That would put (St. Louis) in the highest tax bracket, except for the city of Seattle — higher than even Chicago or Detroit,” he said at a recent forum. “How can we lure people with entry-level jobs who are trying to start families with that type of tax increase?”

Many of the other candidates for county executive support the tax, however, including County Executive Charlie Dooley, a Democrat, 6th District County Councilman Steve Stenger, D-Affton, and Rep. Rick Stream, R-Kirkwood, who voted for the measure in the Legislature.

“It’s about investment in our infrastructure,” Dooley said at the same forum. “It creates jobs and opportunity, it expands our base. That’s one of the things that is really important for economic development.”

“Transportation infrastructure is crucial to the growth of our economy, and the projected 100,000 jobs for working families over the next 10 years (and) $6 billion worth of investment is too hard to pass up,” Stenger said in a news release. “While a regressive sales tax may not be the best funding mechanism, given the choice of either abandoning transportation or this tax, I support job creation.”

Although the ballot language indicates that a priority will be given to projects that improve the safety of roads and infrastructure, nothing in the authorizing legislation requires agencies to prioritize safety in the projects.

Besides fixing roads statewide, the keystone project for the Missouri Department of Transportation, or MoDOT, will expand Interstate 70 from two lanes to three from St. Louis to Kansas City, at a cost of $2 billion to $4 billion.

Of the $6.1 billion in new tax revenue, residents in the St. Louis region are expected to pay more than $2 billion of the tax but get back $1.4 billion of the total spending on new projects.

MoDOT projects can only fix state-owned roads and infrastructure, not roads owned by counties or cities.

Although some of the slated projects, such as improvements to the airport and more sidewalks around bus stops, would have an impact on the entire region, only two projects are in south county, adding up to $4.5 million in spending.

In south county, the projects slated include $2 million for improvements on Gravois Road from Laclede Station Road to Musick Road, at Grant’s Farm and the future location of the new Tesson Ferry Library. MoDOT plans to use funds from the sales tax to install a left turn lane from Gravois onto Musick with other upgrades along that entire length of Gravois to Laclede Station Road, including enhancing traffic flow and safety at Cor Jesu Academy next to the future library site.

“If you ever drive on Gravois, it is going to be a very, very good project that we will all be happy with,” said Tom Blair, MoDOT’s assistant district engineer for the St. Louis region. “There’s definitely a need. Everybody identifies the need. If (the tax does not pass), the need will not go away, and we’ll still have to find other ways. The improvements need to happen.”

Without the sales tax, the state agency does not have the money to make the improvements, which a library traffic study showed are needed for current traffic, even before the library’s new location opens in the fall of 2015 at the busy intersection.

The other major project in south county would provide $2.5 million to connect the Grant’s Trail extension to the River des Peres Trail, contingent on a matching donation from Great Rivers Greenway.