After 13 years of planning, and several months of negotiations with residents and shop owners, the South Street Bridge closes today for reconstruction.

The 85-year-old bridge, which spans 2,000 feet and connects Southwest Center City with University City, is to close at 9:30 a.m. It won't reopen for at least two years.

Decades of heavy use and bad weather left the bridge dilapidated and unable to support vehicles that weigh more than 6 tons, officials said.

Beginning this month, the existing bridge and its support structures are scheduled to be demolished. An entirely new bridge — complete with bike lanes, wider pedestrian sidewalks and overlook towers — will be built in its place.

Activists say that most design and safety issues reported by the Daily News in March 2008 have been resolved, and the $67 million reconstruction plan now meets the approval of residents and business owners.

At the urging of a community group called the South Street Bridge Coalition, the original five-lane design has been replaced with a four-lane design, the speed limit for the bridge will be reduced to 25 mph and an additional pedestrian crosswalk will be added to the ramp and stairway leading from the bridge to the Schuylkill River Park and Trail.

"We needed the bridge to be more pedestrian- and biker-friendly," said James Campbell, a leader of the coalition. "We wanted it to be more than just a high-speed connection to the highway."

Campbell said that the group "couldn't be happier" with the changes made to the original bridge-reconstruction plan.

"The city has been really terrific in terms of trying to meet the needs of the community," he said.

In addition, the concrete roadway will be tinted to look like asphalt (it makes drivers slow down, authorities say) and equipped with reflective pavement markers at the curve on the east side of the bridge. Lights will be installed along the sidewalks, and traffic-signal timings will be optimized for crossing safety.

The left-lane merges from the bridge onto the Schuylkill Expressway will remain, as will the ramps leading onto South Street from the expressway, officials say.

Though community members have raised concerns about the merge-points and ramps — both frequent sites of accidents — city officials said last spring that redesigning or relocating them would be too costly.

While the bridge is under construction, South Street will be closed to traffic from 27th Street to Convention Avenue.

Drivers on local roads east of the Schuylkill will be detoured from South Street to 22nd to Walnut, then over to 34th and down to South. Drivers on local roads west of the Schuylkill will be detoured from South Street to 33rd to Chestnut, then to 23rd and down to South.

The city's Streets Department has advised commuters who rely on the bridge to use public transportation instead.

SEPTA's University City regional-rail station, at South Street and Convention Avenue, serves the R1, R2 and R3 lines and is within walking distance of the University of Pennsylvania, Drexel University, the Hospital of the University of Pennsylvania and the Children's Hospital of Philadelphia. Commuters can access the R1, R2 and R3 lines at 30th Street Station.

SEPTA's Market-Frankford Line stops at 30th and Market Streets, 34th and Market and 40th and Market.

The 11, 13, 34 and 36 trolley routes travel between Center City and West Philly. Trolley stations are located at 22nd and Market Streets, 33rd and Market, 36th and Sansom, 37th and Spruce and 40th Street and Baltimore Avenue.

Drivers on I-76 can use the University Avenue exits — 346A eastbound, 346B westbound — to access Penn and the hospitals. For access to Drexel and the University City Science Center, the eastbound Girard Avenue exit (342) and the westbound University City exit (346A) are recommended.