TAMPA — The bottleneck driving north on the Howard Frankland Bridge is one of the most frustrating and rage-inducing in Tampa Bay.

The interstate drops from four lanes to two at the West Shore interchange, causing backups that can span the length of the bridge. The traffic leads to missed flights, late work arrivals and profanity-laced rants.

But state officials say it's about to get better — just give them two years.

The Florida Department of Transportation will start construction in about six months on additional lanes that officials say will bring relief.

A third through lane will help those continuing on the interstate toward downtown Tampa, while additional lanes on parts of the exit ramp should improve the ride for drivers getting off at Kennedy Boulevard and those heading left toward the airport or the Veterans Expressway. The lanes should be open to drivers in late 2020, officials said.

"It will help those people immediately once it's done," said Richard Moss, the department's director of transportation development.

The extra lane on the interstate, which will be added in each direction, will increase capacity 50 percent. The change should bring "pretty substantial improvement," district transportation secretary David Gwynn said.

The interchange has long befuddled commuters.

"I can't fully understand why it is the way it is now, going from four lanes to two," Nate Matro, 34, said. "It makes no sense at all."

Matro, who lives in Seminole and takes the State Road 60 exit to get to his office, said he has to leave his house 90 minutes before a meeting if he wants to guarantee he'll arrive in time.

"It does seem to me that one lane will make a huge difference," Matro said. "It just seems like its poorly designed for how much traffic comes through there."

Hugh Porter, 35, said the regular traffic jam makes it difficult to predict when he needs to leave for work. As a result, he and countless others are forced to choose between getting on the road an hour earlier than needed or risking arriving late for an appointment.

"It's horrendous trying to get off at that interchange," Porter said. "It should be much easier to commute for a city this size."

The Department of Transportation previously tied the improvements at West Shore to the rest of the now-defunct, multibillion-dollar Tampa Bay Express project. That controversial interstate expansion was put on hold in 2016 because of community backlash.

Gwynn took over as district secretary in 2017 and announced plans to address the traffic snarl at the interchange while a long-term plan was developed. He originally hoped the new lanes would open in 2021, but later was able to move up the start date.

The additional lanes, which are expected to cost about $29 million, are a relatively quick and affordable fix as far as transportation projects go, Gwynn said. The state's bigger plan for the interchange will cost about $1 billion and won't open to drivers for about another decade.

"Rather than sit here and wait until the final project comes, we want to move forward," Gwynn said. "Especially when you can spend $25 to $30 million and get a benefit like that."

The project, which will eliminate some merges, also should make driving through one of the region's most crash-prone areas safer, Gwynn said.

In addition, the department plans to widen a quarter-mile of stretch on State Road 60 near the airport interchange in order to add an extra lane. Construction will start around the same time as the West Shore improvements and is expected to finish in fall 2019.

The $2 million project just south of the Independence Parkway ramp will expand that short stretch of SR 60 from four to five lanes. It should help reduce morning rush hour traffic and make the commute safer by eliminating a southbound merge, Moss said.

As for the West Shore improvements, the state plans to select a contractor in January and start construction in late spring. Construction will last about 18 months, raising some concern that commutes could worsen during that time.

"I imagine I'm going to be doing that commute forever," Matro said. "Even if it's a painful year, I'll gladly take it."

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