Lane restrictions on Interstate 79 appear to be causing traffic headaches on secondary roads being used as unofficial detours.

Washington Pike in South Fayette was bumper-to-bumper for miles Saturday as traffic appeared to be trying to bypass the nearly 4-mile construction zone on I-79 that extends from the Washington County line to Bridgeville exit. Meanwhile, more traffic clogged Route 50 near Chartiers Valley Shopping Center as construction continues on that stretch of roadway.

PennDOT spokesman Jim Struzzi said motorists are encouraged to leave the interstate if they can find different routes to their destinations. Cars were also bumper-to-bumper along the interstate construction zone, especially near the Bridgeville exit.

“If people know an alternate route, then we would obviously want them to do that to lessen some of the impact on the work zone,” Struzzi said. “There’s construction on 50, too. Obviously, you’re going to impact the parallel routes when you restrict lanes on an interstate.”

Weekend lane restrictions on the interstate are expected to continue through November, and work will also be done during weeknights. Single-lane restrictions during the week begin at 7 p.m. and will end each morning at 6 a.m.

The $2.6 million project will upgrade signs and guardrails, patch parts of the concrete roadway and repair three overpass bridges that cross the interstate in that area.

“It’s going to continue through fall, so we would encourage people to find alternate route,” Struzzi said.