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New southbound tunnel ready to open

Drivers aren't sure suffering will end

As the final hours of driving on Boston's elevated Central Artery wind down, today marks the last morning that long-suffering commuters from the north have to sit in the infamous bottleneck on the lower deck, by the FleetCenter.

 

Still, many drivers remain skeptical that the commute into Boston from Andover or Marblehead or New Hampshire will really be helped by the new southbound Interstate 93 tunnel, which is set to open to traffic tomorrow morning.

There won't be a radical expansion in the number of lanes coming into the city from the north, project officials concede. The key difference is that there will no longer be the jockeying for position and merging that has been the defining feature of the southbound commute for decades.

Drivers coming from Medford, Woburn, or points north who take I-93 south will have the choice of the high-occupancy vehicle, or HOV, lane and regular lanes as they now do. They will continue along the lower deck, but instead of bearing left on the elevated structure, they will go straight, toward the Leonard P. Zakim Bunker Hill Bridge.

Just before the bridge, the HOV lane must merge into two lanes of I-93 southbound traffic. But the good news, said Charles F. Sterling, director of traffic operations for the Big Dig, is that drivers coming from the Tobin Bridge will not have to merge with that southbound I-93 traffic. Instead a third lane is added at that point to accommodate them.

"The folks on the Tobin get their own lane," Sterling said.

Similarly, just before those three lanes of traffic plunge into the portal of the new southbound I-93 tunnel, drivers from Storrow Drive join the flow. Another lane is added to accommodate the Storrow Drive inflow of traffic, and no merge is required.

"They won't have to drift in to the left, into the folks already on the roadway," Sterling said. "That includes all the traffic coming from both Storrow Drive and Route 28."

In addition, a major cause of backups coming into the city from the north -- the merging of Sumner Tunnel traffic from the Haymarket ramp, where a state trooper used to be posted -- will be eliminated.

There is no direct highway access from the Sumner Tunnel to the southbound I-93 tunnel, because motorists at Logan Airport heading south are directed to take I-90 west through the Ted Williams Tunnel onto I-93 south, avoiding the Central Artery altogether.

Traffic in the new southbound tunnel will be joined only at one point by merging drivers, coming from the New Chardon Street on-ramp.

The only part of the project that threatens to back up the commute from the north is the point where the new tunnel joins the existing Dewey Square tunnel, which is still being rehabilitated.

In about a year, project officials say, that last part of the $14.6 billion Big Dig will be finished, giving drivers more room throughout the final stretch of the artery.

Big Dig officials say the last cars will travel over the half-century old Central Artery sometime tomorrow morning, and then southbound traffic will be allowed onto the Zakim bridge and into the new tunnel.

Anthony Flint can be reached at flint@globe.com.

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