The North Washington Street bridge replacement might not be so awful with this new fix

The North Washington Street bridge is about to be rebuilt, a five-year construction job that also promises to be a traffic nightmare.JESSICA RINALDI/GLOBE STAFF/file

One of the most disruptive bridge projects coming to a section of Boston will be a bit more bearable, thanks to a late fix by state highway officials.

The North Washington Street bridge is about to be rebuilt, a five-year construction job that also promises to be a traffic nightmare for the 44,000 motorists and thousands of MBTA bus riders who use it every day to come in and out of downtown Boston.

Originally, traffic would be reduced to three lanes — two into downtown, one out to Charlestown — and during some periods, just one in each direction.

But now state officials say they will build a temporary three-lane bridge over the Charles River, next to the existing century-old structure, beginning early next year. The “no-frills” structure will take about one year to build, said John McInerney, director of the highway department’s Boston region, and will allow the state to always maintain at least three lanes of traffic throughout the entire construction period.

Most likely, the temporary structure will merge into the existing bridge on the downtown side of the Charles, McInerney said. That will allow the contractor to accelerate work on the old bridge, cutting the overall construction time by six months. Crews have already begun working to remove and replace the utilities across the old bridge, and will dismantle and replace the bridge in stages, beginning next year.

Once complete, in 2023, the new permanent bridge will have two lanes in each direction, a separate bus-only lane on the inbound side, and separate lanes for bicycles.

But the three-lane pattern on the temporary bridge will at least be familiar to commuters because the existing bridge has already been down to three lanes for most of the last year.

The state is still finalizing plans for the temporary bridge and its installation, and will hold public meetings on it in the coming months. Officials acknowledge the temporary bridge will displace a playground in Paul Revere Park in Charlestown; it will be rebuilt in the same park, further to the west.

They also say the temporary bridge will come at no additional costs. Earlier this year, the transportation department hired J.F. White Contracting to replace the bridge for $177 million, though the state has budgeted to spend above $200 million to cover police details and potential cost overruns.