The Pennsylvania Turnpike Commission warns motorists to change travel plans or brace for a long detour from tonight through Monday during a planned weekend closure of the Northeastern Extension (Interstate 476) in Lehigh and Carbon counties as workers replace a 60-year-old bridge.

The detour will occur from 9 p.m. today through 4 a.m. Monday.

The detour exits are the Lehigh Valley Interchange (exit 56) for northbound traffic and the Pocono Interchange (exit 95) for southbound traffic. The authorized detour route directs motorists to Route 22, Route 33 and Interstate 80.

“Motorists will face a lengthy detour that will add more than an hour to their travel times,” said Pennsylvania Turnpike CEO Mark Compton. “As a result, we strongly advise customers to avoid this area or plan for extra travel time during the detour weekend.”

Local travelers heading southbound on the turnpike will be able to drive past Exit 95/Pocono and continue to exit 87/Route 903 “E-ZPass Only” or exit 74/Mahoning Valley. The turnpike will be closed southbound at Mahoning Valley.

During the closure, crews will demolish and replace a bridge at milepost 57.66 carrying the Northeastern Extension over Crackersport Road in South Whitehall Township, Lehigh County. The 131-foot-long bridge opened to traffic on Nov. 7, 1957, and today carries roughly 30,000 vehicles per day.

Compton said the turnpike is using a proven engineering technique called Accelerated Bridge Construction that allows workers to replace a bridge in one weekend rather than a year or more of construction. During the 55-hour construction, workers will demolish the old bridge and slide the new spans into position. For the past several months, crews have been constructing the new spans next to the existing bridge.

“The Accelerated Bridge Construction process is a safe, cost-effective way to replace bridges within a short time frame while improving safety for workers and motorists in construction zones,” Compton said. “Last month our bridge-replacement project and related detours in Beaver County ended two hours ahead of schedule. We are hopeful next weekend goes equally as well.”