PAWTUCKET — The detours that will begin routing trucks through city streets today to keep them off a weakened Route 95 bridge could be needed for several years, a state Department of Transportation official said yesterday.

The DOT’s acting chief engineer, Kazem Farhoumand, also said the agency will carefully watch how its detour plan works during the next few days and will be ready to adjust it if necessary.

The detours are intended to keep heavy truck traffic off the Pawtucket River Bridge, which the DOT has posted for a maximum of 22 tons because of the bridge’s deteriorated condition. The DOT said it would post the highway last night, barring those trucks from the bridge. It will also close the northbound George Street entrance ramp, also because of deterioration of the bridge.

Farhoumand said that the agency has not yet decided whether, or how much, to repair the bridge until it can be replaced. Inspections have shown a variety of problems, mostly due to rust, affecting steel members scattered throughout the structure.

He said that the 22-ton limit effective today, together with the closing of the entrance ramp, will keep the bridge safe. The DOT’s next step is to decide whether it is worth making repairs that would allow raising the weight limit above 22 tons until the bridge is replaced.

Asked during a news conference if the detours could continue for as long as five years, he said, “I do not know. We haven’t finished our analysis yet.” But he said that a person guessing that it could take that long “could be right” if the DOT concludes that “it is not cost-effective to repair the bridge.”

There are large sums involved. Farhoumand estimated the cost of a new bridge at $40 million to $50 million. He said the DOT has already spent about $500,000 on repairs this year. The state, meanwhile, had tentatively budgeted $5 million to rehabilitate the bridge, a project now in question.

Asked whether the situation amounts to an emergency, Farhoumand said that the answer depends on your point of view. “If you’re one of those truckers, it is an emergency. From a safety point of view, it is not” an emergency.

The DOT wants truckers going anywhere but the immediate Pawtucket area to use highway detours, such as routes 146 and 295, to get around the bridge. Locally, it has set up detours on local streets. Southbound traffic is to leave Route 95 at exit 30, Roosevelt Avenue, in Central Falls, and head south on that street, across Goff Avenue, Pine and Garden streets to the ramp from Cedar Street to Route 95 southbound.

Northbound truck traffic will be directed off Route 95 at Exit 27 and follow Marrin Street, along the highway, and Division Street to the Division Street Bridge, which crosses the river just south of the Route 95 bridge. The DOT said it will make that bridge one way, making two lanes headed east, to carry northbound truck traffic and the traffic that would normally use the George Street ramp onto Route 95 northbound.

Farhoumand said there may be traffic congestion at first as drivers get used to the changed traffic pattern. People have their habitual routes to work and elsewhere. “Once you change that, there is a learning curve,” he said, as people adapt.

The DOT will have personnel on the scene today, he said, and local police will direct traffic and help keep it moving. He said that the DOT will “respond very quickly” if more signs are needed or traffic-light timing needs adjustment. What the agency can’t do during the rest of the week, he said, it will do during the weekend.

Also, he said, if people who don’t need to be there would avoid the detour routes, he said, “We would certainly appreciate that.”

Will it work?

Paul Kennedy, a spokesman for the Rhode Island Trucking Association, thinks it might — if the DOT has the right signs up.

“The trucking industry is basically used to this stuff,” he said. Bridges and roads are regularly closed and big accidents block the highways. Truckers will find their way, “as long as there’s proper signage.”

“It’s the through trucks that I’m concerned about,” he said. Truckers might be coming from the Carolinas headed for Boston, and “if the signage isn’t there, they’re going to end up going through the center of Pawtucket.”

That worries him. Big trucks going through local streets and pedestrians who aren’t used to them could be dangerous combination, he said.

blandis@projo.com