There is an official Allegheny Trail Alliance page for Open and Closed sections.
Note: Most people who ride these trails are trying to avoid traffic; you won’t want to ride bikes on the detours, and we concur. However, some people will decide to bike the detours anyhow. If you do ride the detours, be careful, and wear your helmet.
Remaining Gaps updated 04/2020
There may be two significant gaps in the trail between Pittsburgh PA and Washington DC:
Wintertime Gaps (Mid December to Early April)
Frostburg MD – Deal, PA (9.3 Trail Miles)
The segment from Frostburg to Deal (9.3 miles) is closed during the winter (Dec. 15, through April 15th ). The doors on the Big Savage Tunnel are closed and locked to prevent ice build-up from damaging the tunnel. We recommend driving these roads
High Water Gaps
Dam Four Detour on the C & O Canal (2.7 Trail Miles)
The 2.7-mile segment from Dam Four to McMahon’s Mill floods during high water. There is a standard detour on rolling country roads. The detour is well marked and involves climbing out of the valley on a steep road, traversing lightly traveled roads with rolling hills, and then a steep descent back to the river. Depending on the height of the water, the detour may be extended to the next descending road.
Obsolete detours
East of Paw-Paw Tunnel (about 1.2 miles)
The gorge just east of Paw Paw Tunnel has steep sides. This winter (2012-2013) there was a landslide that blocked the trail. The Park Service then inspected the rest of the hillside and discovered several sections that were poised to landslide. As a result they have closed the gorge to the east side of the Paw Paw Tunnel. The trail will probably be closed through the summer (2013). One can still enter and pass through the tunnel from the west end, but the trail is blocked shortly past the east exit. The detour uses the Tunnel Hill Trail, which goes over the top of the mountain. The elevation change on the Tunnel Hill Trail is about 360 ft (250 m) and has several steep sections. See the elevation profile.
Southside Pittsburgh PA – WaterFront Shopping Center, Homestead, PA, (about 1.6 miles)
The 1.6-mile segment from Southside Pittsburgh through Sandcastle to the Waterfront Shopping Center was opened to the public in 2013. If this section becomes closed, we recommend that you start or end your trip in Homestead. The various routes between Southside and the Waterfront are narrow, with no shoulders and high-speed traffic. We would never ride them even on a Sunday when the Steelers are playing in town.
Wide Water near Great Falls, VA (0.7 Trail Miles)
The short stretch where you had to carry your bike over rocks and which was closed in 2005 for construction, was officially opened April 29, 2006. No longer will you have to climb the hill and traverse the stairs to the Aqueduct.
Cumberland MD – Woodcock Hollow (9.33 Trail Miles)
The 9.33 mile segment from Cumberland MD to Woodcock Hollow MD was opened to the public December 14th 2006. The trail is passable for the entire 9 miles. You may take bikes on the train (make reservatons). We definitely recommend this alternative – the train ride is great, and the road ride isn’t. On this road detour, there is a very busy half-mile with absolutely no shoulders and lots of high-speed traffic. A detour is no longer necessary. However, there is a page describing this detour, in case there is a future trail disruption that requires the detour.
Woodcock Hollow – Frostburg MD – (5.86 Trail Miles)
A portion of the bike trail along the Western Maryland Scenic RR between Cumberland and Frostburg was surfaced in 2005. The trail from Frostburg use to (2005) end at Woodcock Hollow Road. A detour is no longer necessary. However there is a page describing this detour, in case there is a future trail disruption that requires the detour.
Deal – Meyersdale (about 12.0 miles)
Trail is now completed in this section. A detour is no longer necessary. However there is a page describing this detour, in case there is a future trail disruption that requires the detour.
Ft Hill – Confluence (about 8 miles)
Trail is now completed in this section. A detour is no longer necessary. However there is a page describing this detour, in case there is a future trail disruption that requires the detour.
Ohiopyle High Bridge (0.02 Trail Miles)
There was repair work to the High Bridge at Ferncliff in Ohiopyle State Park in 2006. If the bridge is ever closed again, bikers can travel the Great Gorge Trail to Kentuck Rd. – then State Route 381 into Ohiopyle where you can pick up the other side of the bike trail.” See the State Park map (PDF 583 KB).