If Charleston County Council gives final approval to the half-cent sales tax referendum Tuesday, voters will decide on Nov. 8 not only if they want better roads but also if they want to take their public transit system to the next level.

The $2.1 billion raised for transportation and greenbelt projects would include $256.4 million for the Charleston Area Regional Transportation Authority to create its first bus rapid transit line, as well as $353 million more to improve its existing system.

The specialized bus rapid transit line connecting Summerville to downtown Charleston would use larger buses than CARTA’s standard fleet and would travel primarily on bus-only lanes on Rivers Avenue. Buses also would be synchronized with stoplights, giving them an edge over car traffic.

Compared with commuter rail and light rail systems, it’s the most cost-effective mass transit option to ease congestion along the Interstate 26 corridor and Rivers Avenue, according to a study conducted by the Berkeley-Charleston-Dorchester Council of Governments.

Charleston, like most medium-size U.S. metro areas, has a transportation network dominated by cars — and growing congestion. The proposed referendum marks the second time in 12 years county voters have been asked to raise the sales tax by a half percent to address the problem.

As with the 2004 referendum, most money would go toward improving and expanding roads. However, the sizable sum proposed for CARTA and the bus rapid transit line in the latest plan signals that local authorities are looking increasingly toward public transportation to solve traffic problems.

The question is whether voters feel they would benefit from a bus rapid transit line, either by using it themselves or by believing it could take enough cars off the road to make a difference.

There are nearly 30 bus rapid transit lines either in operation or under construction in the United States, and none has failed, according to Christopher Van Eyken, senior transportation planner for the Institute for Transportation and Development Policy.

“A few U.S. cities that haven’t traditionally been strong transit cities have implemented BRT corridors to great success,” he said. “It’s comparable to light rail at a cost that’s lower per mile. I think that’s one of the big benefits. It’s also more flexible.”

County Councilwoman Colleen Condon, who serves on the CARTA board, said the bus rapid transit line “is like having a train on wheels.” She thinks it could lure more “choice riders” to CARTA, which now primarily serves “necessity riders,” those who rely on buses as their only form of transportation.

“Those folks will put up — for better or for worse, because they don’t have a choice — with buses that run late or buses that only run every 90 minutes,” she said. “The only way we can have a meaningful effect on all of our roadways is if we have a system that is really good enough for choice riders.”

The new sales tax income would pay for only a small part of a new bus rapid transit line. The federal government is expected to pick up about 80 percent of the estimated $360 million it would cost. The sales tax funds would provide a $72 million local match for construction, plus funds to operate it and potentially expand it, according to Ron Mitchum, executive director of CARTA.

The remaining $353 million of sales tax money proposed for CARTA would allow the system to replace its aging buses, add modern amenities such as smartphone apps and mobile ticketing, and create a long-term financial plan.

Currently, CARTA’s $20 million budget is just enough to run and maintain its fleet of aging buses, some of which have logged more than a million miles.

“(The current budget) doesn’t give us a lot of room for capital replacement of vehicles, match money for transit amenities like signage and shelters, and some of the technology like apps and mobile ticketing,” Mitchum said. “We can continue to operate with the resources that we have, but we can’t really grow the system very much, if at all.”

CARTA Chairman Mike Seekings, who also is a Charleston city councilman, said “there’s a lot on the line” for CARTA in the half-cent vote.

“We have to replace our fleet, and currently we have no funding for it,” he said. “We have to start having a reserve fund so we can do regular maintenance. We can’t keep running buses for a million miles. If this passes, we will be able to have a long-term plan and show it to the world and say, ‘Look, here’s how we’re going to fund it.’ Right now, we don’t have one.”

A lack of financial planning has led to big shortfalls. In June, County Council gave CARTA $5.6 million after the agency fell behind on payments to the company that operates its buses.

Last year, council forgave $7.6 million in loans made to CARTA between 2006 and 2012. The county had advanced the money to the authority because it faced major challenges with cash flow and capital replacement.

County Councilman Dickie Schweers, who was on the CARTA board eight years ago, said the agency needs more than money — it needs better management.

“In my opinion, that (loan forgiveness) would have never been necessary if CARTA would have improved efficiency over the last decade,” he said. “There have been routes that have been underperforming for at least a decade now that are still underperforming, and there’s just no political will to either eliminate or greatly reduce those routes.”

Seekings said the board recently streamlined routes and will continue to do so. But in some cases, empty buses can be a complicated problem to solve.

“Where we run our buses, some of that is mandated by the federal funding we get. We have to service the communities that we’re funded for,” he said. “Our ridership is growing and our routes are becoming much more efficient and will get more so. It’s a challenge, there’s no question about it.”

Condon said efficiency is always a topic of discussion when council considers funding CARTA improvements.

“There are always comments about CARTA, some who want more service, some who want efficiency,” she said. “This referendum, I think, will absolutely address the concerns of both sides.”

Schweers agreed.

“Hopefully, the marriage of the bus rapid transit to CARTA, that will actually yield some efficiency gains,” Schweers said. “Unless we want to go the route of Atlanta, and end up with a 12-lane interstate, we have to come up with a solution that works.”

Reach Abigail Darlington at 937-5906 and follow her on Twitter @A_Big_Gail