HARRISBURG, Pa. -

An 11-mile stretch of  the Pennsylvania Turnpike's southbound lanes will be closed  for six hours Sunday, between the Lansdale (Exit #31) and Mid-County (Exit #20) interchanges.

The road is being closed to protect drivers and workers during the installation of three overhead signs at mileposts A20.6, A21.1 and A22.3 in Montgomery County.

But it's being done in the middle of the night to minimize the impact.

At 12:01 a.m. Sunday, southbound traffic will be diverted off the toll road, also known as Interstate 476, at the Lansdale Interchange.

By 6 a.m., the detour will be lifted and the Northeast Extension reopened to southbound traffic.

Northbound I-476 will remain open to motorists heading toward north from the main east/west Turnpike mainline or the Mid-County Interchange.

Pennsylvania State Police and turnpike personnel will be positioned at the Lansdale Interchange to assist motorists.

 In case of inclement weather, the closure will be rescheduled on Aug. 10 with times and detours still applicable.

Travelers can tune to radio 1640 AM for detour information and traffic conditions or call the Turnpike Roadway Information line at 866-976-8747.

Changeable message signs also will provide updated information regarding closures and detours. Motorists are encouraged to plan accordingly and to dial *11 on mobile phones for emergencies.

The Pennsylvania Tunpike Commission recommends a detour for anyone who will be traveling southbound on I-476:

Exit at Lansdale Interchange (#31). Turn left onto Sumneytown Pike. At the second light, turn left onto Forty Foot Road (State Route 63-east). Travel 1.5 miles and turn right onto Welsh Road (State Route 63-east) to U.S. Route 309-south to re-enter the turnpike at the Fort Washington Interchange.

Travel east on the turnpike (I-276) to get to Philadelphia and New Jersey.

Travel west on the turnpike  to get to Harrisburg and points west.

Motorists bound for I-476 south (Blue Route) to I-76 and I-95 should also follow the turnpike westbound from Fort Washington, exiting the turnpike at the Mid-County Interchange (Exit #20) to continue southbound on I-476.

Travelers can get turnpike traffic alerts by calling 866-976-TRIP (8747) or visiting the live Travel Conditions Map . The Turnpike’s smartphone app, TRIP Talk, streams audio advisories to iPhone and Droid users so they can keep their hands on the wheel and eyes on the road.