ST. PETERSBURG — The newest hope for transportation in the Tampa Bay area is a bus rapid transit system projected to cover the 41-miles separating St. Petersburg from Wesley Chapel and attract 4,500 new riders at a fraction of the cost of light rail.

Also known as BRT, it was identified as the bay area's best bet to bring mass transit to the region by a 2½-year study conducted by Jacobs Engineering at the behest of state and local officials. The plan was unveiled Friday to political and business leaders and the public.

But that would be just the start of a transportation makeover for the region, supporters said.

"This is not the ultimate endgame for transit in the Tampa Bay region," Florida Department of Transportation local secretary David Gwynn said. "It's nothing even close to that ... What this will hopefully be is a first step."

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Jacobs also outlined what kind of system the bay area should build after BRT: a passenger rail system connecting downtown Tampa to the University of South Florida using 9 miles of existing CSX tracks.

PREVIOUS COVERAGE: CSX's offer finally opens the door to commuter rail in Tampa Bay (Oct. 4, 2015)

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BRT is a transit system where buses use dedicated lanes to bypass traffic, but passengers still board at train-like stations. These would be expensive, high-ends buses, said Jacobs executive Scott Pringle.

"We're not talking about your everyday bus," he said. "We're looking at something that looks like a train, behaves like a train."

But it would cost far less than a train. That's why many local leaders have given up on their dream of building a light rail system to focus on BRT. They're also hoping to attract federal dollars to help pay for it.

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Referendums to bring rail to Tampa Bay failed in Hillsborough County in 2010 and in Pinellas County in 2014. In 2016, the Hillsborough County Commission decided to not even give the voters a choice and killed it before it could go to the ballot.

A key money-saver for this version of BRT is that it would utilize the interstate shoulders to create bus lanes. By using existing right-of-ways, Jacobs engineers project the cost would drop to about $455 million.

That's about $2 billion cheaper than if the buses ran in the median of the interstate, and about $4 billion cheaper than the projected cost of light rail.

"When we incorporate that shoulder running concept, you can see we're dramatically reducing our overhead costs … easily dropping over a billion dollars of infrastructure," Pringle said.

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The longest trip projected along the route would be about 90 minutes to travel the full 41 miles from the Wesley Chapel station to the downtown St. Petersburg station.

The new system could attract 4,500 new riders — that is, people who aren't using the counties' existing bus systems. They would have their choice of using 21 stations along the 41-mile route.

The buses would run along the interstate shoulder in Pinellas, then cross the Howard Frankland Bridge using the state's proposed toll lanes on a future eight-lane rebuild of one of the spans.

Once in Hillsborough, they'd travel in the expansive median of I-275 between the Westshore area and downtown Tampa. That corridor was set aside during the recent interstate expansion for a transit system.

There could also be elevated stations near Westshore Boulevard and at Howard and Armenia Avenues inside that corridor.

The BRT buses could exit the interstate in downtown Tampa to connect with the streetcar system.

For those headed north, the bus would then get back on I-275 and use the interstate shoulder to reach USF. To continue the journey to Pasco County, it could join regular traffic or use the shoulder of I-75.

The consultant said a BRT line could become a reality as soon as five years from now. However, the new, eight-lane Howard Frankland — which will add managed toll lanes the new buses could use — won't be completed until 2024 at the earliest, according to DOT.

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Friday's rollout was the start, not the end of the plan. Now Jacobs will take its show on the road, give its presentation to the public and gather feedback on the concept. That input will be used to shape the final plan.

Then if government leaders are willing to move forward, each county will have to decide how to pay their share. Pinellas, Hillsborough and Pasco would have to split the annual $8.6 million in capital and operating costs.

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Initial reaction was positive but cautious.

"This is relatively low cost. This doesn't mean we have to do a sales (tax)," Hillsborough County Commissioner Pat Kemp said. "We do need to put our general dollars in this. We don't need to be afraid of a sales tax. But a sales tax can be over and above."

Forward Pinellas executive director Whit Blanton, who leads that county's transportation planning agency, said this project has a better shot of earning federal funding.

"When we talk about going for federal money it is not only a very competitive but risky process…," he said. "We've got a project that really does lower the risks."

Tampa City Council member Harry Cohen said this project, more than previously proposed options, seems doable from a financial perspective.

"It is not so expensive that it really is out of the realm of us figuring out how to pay for it," Cohen said.

Those who have opposed past transit proposals watched the presentation warily.

Hillsborough Tea Party co-founder Sharon Calvert urged leaders not to apply for federal funding.

"Once federally money is taken, you're really tied to what you have," she said. She added: "We need flexibility to move forward with it.... Flexible enough to eliminate it, reduce it and change it."

Barbara Haselden, who organized No Tax For Tracks and helped defeat the Greenlight Pinellas transportation sales tax in 2014, said she hoped this meant rail was officially off the table in Tampa Bay.

But other members of the public encouraged leaders to press on.

"Don't be swayed," Safety Harbor resident Dave Kovar said. "Listen to the good."

Pringle reiterated that BRT project is only the first step. Jacobs is studying other transit options that could also be built in the bay area.

"It's not a one-and-done proposition," he said.

Contact Caitlin Johnston at cjohnston@tampabay.com or (727) 893-8779. Follow @cljohnst.