(TNS) — A showdown is rolling down the tracks for South Dade transit, with the county mayor ready to build a $300 million network of modernized buses designed for group boarding, advanced ticketing and other features aimed at imitating a commute on Metrorail but at about a quarter of the cost.

Creating a "rapid transit" bus system for South Dade could win federal funding fairly quickly and allow operations to start in 2022, according to county estimates. But the politics could be daunting: Mayors and elected representatives from the region are demanding Miami-Dade fulfill a promise for a Metrorail extension, a project that would cost more than $1 billion.

"People in the south understand that if they settle for a bus, they'll never get a rail," said Kionne McGhee, a Democratic state representative from South Dade. "Nobody wants buses."

The two sides have been sparring for several years, but on July 19 Mayor Carlos Gimenez is set to ask for the first definitive vote on the issue. His administration plans to ask the county's transportation board to endorse building the "bus rapid transit" system along the 20-mile South Dade busway, an existing two-lane highway that's reserved for county buses and already has growing routes in a system losing passengers elsewhere at an alarming rate.

If the Transportation Planning Organization, a 25-member board that includes all 13 county commissioners, takes on the South Dade issue, it would set up a milestone for the 2016 SMART Plan. That was the planning reset aimed at addressing more than a decade of broken promises on extending Metrorail — pledges made to voters in exchange for approving a half-percent transportation sales tax in 2012. The SMART plan launched consultant studies of six major commuting routes, with the aim of analyzing which transit mode (Metrorail, light rail, rapid transit bus, even autonomous vehicles) made the most sense for each.

Miami-Dade is ready to conclude the South Dade SMART study by recommending rapid transit bus for that corridor. The transportation board could accept that recommendation, or vote to overrule the administration and select extending Metrorail for South Dade. The board could also delay the decision altogether and conclude the July 19 meeting without a decision.

If Gimenez wins the board's backing, the plan is to apply for federal funding within weeks, with hopes that Washington and Florida would agree to cover about two-thirds of the price tag in 2019.

Backers are pitching the rapid transit option as a major upgrade, with express buses using bay doors that board like a train at 14 stations with permanent structures for shade and massive fans to combat the heat. While buses on the busway recently were given priority at intersections through transmitters that went online in late 2017, the new plan would boost that system with rail-like crossing arms to block traffic and let buses speed through intersections. "In essence, that bus would never have stop," said Alice Bravo, Miami-Dade's transportation director. Passengers would buy tickets ahead of time, like on Metrorail, and have access to limited stops when choosing the rapid-transit route to the Dadeland South Metrorail station.

The bus stations are designed to convert to train platforms if Miami-Dade opts for a rail extension years later, but advocates see the bus option as the only realistic way to give commuters a significant assist.

"Right now, we'd like to have transit in our lifetimes," said Jeff Porter, mayor of Homestead, a South Dade city that endorsed the rapid transit bus plan.

Bravo said the stations included in the new South Dade plan were designed to be iconic enough to attract residential development along the depots.

The new bus proposal departs in some ways from the blueprint Gimenez unveiled last year as a short-term alternative to extending Metrorail. At the time, he called trains "19th century technology" and warned autonomous vehicles would make rail service obsolete. His bus plan at the time proposed pursuing rapid-transit bus systems in the south and the northern parts of the county, with dedicated lanes along 27th Avenue to the Broward County line. He also floated the possibility of air-conditioned bus stations and some overpasses to avoid cross traffic altogether.

Now the administration wants to apply for federal dollars on the south corridor immediately, with a plan for the north corridor waiting until that SMART study is completed later this year. Overpasses were seen as needing to be too large once the SMART consultant hired for the southern corridor, AECOM, finalized the calculations, Bravo said.

Despite the lack of air conditioning, she said the preferred option for the stations are more expensive than in the original plan, given the larger, iconic shells surrounding the platforms. She said the climate-control option required too much glass, and couldn't cover enough area to protect passengers transferring to and from local bus routes nearby.

"Now they're in a bigger station that protects everyone," she said. "It's going to be cool there." Even so, the county has an option with an air-conditioned station that includes a more modest station design.

The AECOM analysis shows 55 percent of the people who attended meetings on the South Dade plan wanted rail and not bus, according to tallies from the public sessions. Extending Metrorail would draw far more passengers: 40,000 trips a day, compared to 25,000 for the upgraded bus system.

But the costs show a much wider gap: between $250 million and $300 million to build the rapid transit bus system, versus $1.3 billion to $1.5 billion for nearly doubling the 25-mile existing Metrorail system along the South Dade busway. And that's just for construction. AECOM estimates rail operating costs would be about 80 percent higher than for the new bus system.

AECOM also dramatically increased the cost estimates from what Gimenez had forecast in his July 2017 memo, which had the north and south Metrorail extensions together costing about $1.5 billion to build. An analysis by the Transportation Planning Organization used those estimates to plug in a payment schedule for extending Metrorail in both directions and found an $18 million yearly gap. And that assumed Florida picking up about half of the construction costs.

The Gimenez administration is warning that Washington is unlikely to fund a Metrorail extension to the south, given the South Dade corridor is too suburban and rural to attract enough riders to compete with rail systems being proposed for areas with more residents per square mile.

"The consultant's opinion is that the density and the ridership are too low for rail," Bravo said. Even so, she said the bus system itself could help with future rail efforts if Miami-Dade could show Washington increased demand for transit along the busway.

"For rail, you just make that station longer," she said, pointing to the undulating metal roof of one station in a rendering in a county proposal. "The only cost you would incur is building the central platform a little higher, the day you convert to rail."

©2018 Miami Herald Distributed by Tribune Content Agency, LLC.