It’s only a 4½-mile stretch of road.

But when it’s rebuilt and repaved by late 2015, the strip of Interstate 35E north of downtown St. Paul to Little Canada Road will feature the east metro’s first MnPass toll lanes, allowing commuters an opportunity to better navigate rush hour.

The MnPass project, the third in the Twin Cities, is the key piece of a $115 million freeway makeover that promises to reshape I-35E while aiming to reduce traffic congestion and smooth the rush-hour traffic flow.

A significant step in the reconstruction takes place next weekend, when crews shut down more than 4 miles of the freeway in both directions to begin removing several bridge overpasses.

The first toll lanes to be built from scratch and the shortest of the metro area’s three MnPass lanes, the I-35E stretch from I-94 in downtown St. Paul to Little Canada Road was targeted because of its high congestion on a key route between the northern suburbs and downtown, said Bobbie Dahlke, a spokeswoman for MnDOT.

Under the MnPass system, bus riders and car poolers can use the lanes for free, while solo drivers can use them during rush hour for a fee. Those solo motorists must buy a transponder that electronically sets and charges the fees, which vary depending on traffic volume, and average about $1.25, Dahlke said.

The main purpose of MnPass lanes is not to make a profit, she said, but to reduce traffic congestion.

The other two Twin Cities MnPass lanes, on I-394 west of Minneapolis and on I-35W south of the city, have proved their worth to that end, she added.

While the I-35E MnPass lanes will be the shortest in the Twin Cities, that could change. A Federal Highway Administration grant to MnDOT is funding a study that is ­exploring the feasibility of extending the lanes 4.8 miles ­northward to Hwy. 96 in White Bear Lake. Preliminary results are expected early this summer.

The decision to build the MnPass lanes came about when MnDOT started making plans to reconfigure the Cayuga Street interchange south of Maryland Avenue. Coordinating the new construction with that project saved both money and traffic disruption during construction.

This will be second construction year for the I-35E project, Dahlke said, and MnDOT hopes to have everything wrapped up by late next year.

Are MnPass lanes fair?

As with many major road projects, the I-35E overhaul has had its share of issues.

It briefly bogged down in the 2011 Legislature in debate over creating what amounts to a toll road.

Sen. John Marty, DFL-Rose­ville, in whose district the project runs, voted against letting MnDOT create new toll lanes. Marty said his argument is mostly philosophical: “It doesn’t seem right that those with more resources can bypass congested traffic,” he said.

A better alternative for reducing congestion, Marty said, would be to place more emphasis on carpooling, dedi­cated bus lanes and better traffic management. There is also an issue of enforcing the MnPass lanes, making sure solo drivers aren’t cheating the system.

Though Marty said he hasn’t heard from constituents complaining about the project, neighbors living near it have raised concerns.

Tom Day lives on ­Savage Lake, just west of I-35E and north of Hwy. 36 in Little ­Canada. He wasn’t blind to the fact that his neighborhood was near a freeway when he moved there, but he said the growth of traffic on I-35E has steadily made the noise and quality of life much worse.

“We’ve lived here for 17 years, and when we first came here it was substantially quiet­er,” he said. “Every time they have upgraded the freeway, the noise has steadily crept up.”

His concern with the new expansion is that noise barriers that are to be installed won’t be effective. A retired electrician, Day takes a scientific approach to documenting how noise has increased.

“We’ve picked up 6 to 8 decibels [of noise] in our back yard just in the past few years,” he said. “When traffic is at its peak, you can’t have a normal conversation in our back yard. You have to shout at each other.”

The project’s original plan also put the Ramsey County Board and neighborhood activists at odds because, among other things, the plans cut off a pedestrian tunnel running under the freeway.

“We had major concerns with the original design,” said Leslie McMurry, director of the Payne-Phalen Planning Council. “That is now being addressed.”