Commuting across the Howard Frankland Bridge is already a slog.

And state officials are poised to make the congestion even worse — unless you can afford to buy your way out of it.

The Florida Department of Transportation plans to add a toll on one lane in each direction, creating "express lanes" that could cost as much as $6 to use. Drivers who don't pay will have three lanes instead of the current four.

State officials say this has been public knowledge for years, part of a controversial highway expansion proposal called Tampa Bay Express, or TBX, that includes rebuilding the bridge.

But transportation activists and even top officials who voted on the proposal thought TBX would add extra lanes to the new bridge for tolls — not replace lanes that already exist. After three years of presentations and meetings, even veteran urban planners who were involved in the process were stunned to learn that the state's plan will shrink the number of free lanes for drivers.

"I certainly didn't think they were going to reduce the number of lanes," said Tampa City Councilman Harry Cohen, who sits on the Hillsborough County Metropolitan Planning Organization and voted to allow the project to proceed in June.

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"My understanding was we were increasing capacity," said Kevin Beckner, a Hillsborough County commissioner and MPO member who voted against it.

"I'm positive that was not brought to the MPO," said Les Miller, MPO chairman and Hillsborough County commissioner. "My understanding for this whole process was that we would have additional lanes."

FDOT administrators contend they have said all along that the new bridge will have one fewer free lane. They argue it doesn't technically remove any capacity from the bridge because they consider only three of the Howard Frankland Bridge's four lanes to be for "general use."

The state calls the fourth lane, the one nearest the water, an "auxiliary lane." Its purpose is to connect the on- and off-ramps in Pinellas and Hillsborough, officials say, not to carry through traffic.

But thousands of people drive it every day.It's not a "breakdown lane" or a shoulder. It spans the length of the bridge and is, in fact, the same width as the "general use" lane next to it.

And while official documents often refer to it as an auxiliary lane, some FDOT records also describe the bridge with four "travel lanes."

"Nobody's been duped," said Debbie Hunt, director of transportation development for FDOT's Tampa district. "I'm not sure why anybody thinks it's different. I'm truly baffled."

Transportation activists say FDOT misled the public by promoting a more expansive version of TBX with four free lanes, two tolls and room for mass transit like a light rail connecting the two counties.

"Why is FDOT spending half a billion dollars on a new Howard Frankland Bridge that provides no new capacity and takes away general purpose lanes solely to add tolls?" asked Michelle Cookson, a resident who is part of a coalition trying to stop TBX.

"The department has said that about all the other segments, that they're not taking away a general purpose lane, that this is a new lane," said Beth Alden, executive director of the Hillsborough MPO. "I think it would be really easy to have gotten a different impression about what this bridge is going to be."

Rebuilding the bridge is just one part of TBX, a $6 billion project that adds nearly 100 miles of toll lanes to Tampa Bay and has been the subject of dozens of contentious meetings between state officials and the public since January 2015. It has been criticized for tearing down homes in minority communities and for failing to include any mass transit options.

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Drivers won't lose a free lane anywhere else along the project, state officials told the Tampa Bay Times.

Several top officials, including those who support TBX, said they understood FDOT's plan for the bridge for the first time at a Sept. 14 meeting.

"I was surprised to hear them call one of the lanes an auxiliary lane," said Alden, who has a master's degree in urban planning and has studied transportation issues for 20 years.

"I was a little bit concerned about what I was hearing because it seemed to me what was being proposed was less robust than what I recall," said Cohen, the city councilman.

Cohen said he was unaware of the more modest plan when he voted in favor of TBX in June. Beckner voted against TBX and said the proposal to reduce the number of free lanes makes an already difficult commute even worse.

The toll will automatically fluctuate between 15 cents and $2 a mile as traffic gets better and worse. The concept is already in place in South Florida and rises to $10.50 a trip at rush hour.

The higher prices are meant to discourage too many drivers from using the lane so it never gets congested. Drivers who cannot afford the toll will have to crowd into the remaining three lanes, which will be slower by design.

At its most expensive, the toll lane could cost drivers $6, or more than $3,000 a year, to cross the Howard Frankland during a daily rush-hour commute.

"I don't think it would do anything to reduce congestion," Beckner said. "That's just a revenue generator."

Even the master plan for the project, posted on FDOT's website, shows a more expansive version of the Howard Frankland: four general use lanes and two toll lanes in each direction.

Again and again in the 172-page document, state officials refer to the wider bridge with no reduction in lanes. This is called the "ultimate" option.

It also refers to the smaller version of the bridge as a "interim" plan, but much less prominently.

Not everyone was confused. Unlike the elected officials who voted on the project, two business leaders said FDOT made it clear to them that the interim plan — converting the auxiliary lane to a toll lane — was the objective.

"There's always been whatever they call it, the interim plan, the starter plan, the ultimate plan, the master plan," said Ann Kulig, executive director of the Westshore Alliance. "We just focus on whatever the next step is.

Rick Homans of the Tampa Bay Partnership, a strong advocate for TBX, said business executives care more about the bottleneck at Westshore, where four lanes currently narrow to two, than the number of lanes on the bridge. The plan aims to fix that by adding an extra through lane at the interchange.

"You don't need to spend hundreds of millions of dollars to add additional lanes to the bridge if you fix the root of the problem, which is a poorly designed interchange," Homans said.

The morning after the Times first questioned FDOT officials about the differing plans, the agency took to Twitter with a new social media campaign: #FranklandFriday. The state used the hashtag to share documents showing the scaled-back interim plan. One tweet explained what an auxiliary lane is.

Hunt, of FDOT, said the department's goal is still the bigger version of the project, but that will happen only after both Hillsborough and Pinellas counties agree on a mass transit system to cross the bay — an agreement that has eluded the region for two decades.

If that ever happens, the state will start construction on a third bridge — this time, with the extra lanes. The segment they're proposing now would be used for mass transit.

Until then, drivers will have a choice: Sit in even worse congestion. Or pay up.

Contact Caitlin Johnston at cjohnston@tampabay.com or (727) 893-8779. Follow @cljohnst. Contact Anthony Cormier at acormier@tampabay.com or (727) 893-8308. Follow @Cormier_Times.