A new stretch of road is being planned for the Pennsylvania Turnpike in the US. Progress is being made with the plans to replace the Allegheny Tunnel in Somerset County.
The Pennsylvania Turnpike Commission recently announced that it would opt for a route running to the south of the existing tunnels. This followed an analysis of several options, with the southern route having the lowest cost, US$332 million, as well as less of an environmental impact.
The Allegheny Tunnel stretch now features twin tubes measuring around 1,850m in length but one tube in particular is no longer considered fit for purpose. The first of these tunnels opened in 1939, a stretch of the original Pennsylvania Turnpike, with a single lane in either direction. The second tunnel was opened in 1965 to meet increasing traffic demand, becoming the eastbound section and featuring two lanes, while the original link became the westbound section.
The problems with the original tunnel stretch and approach roads were first identified in 1995. Restrictions on trucks able to use the tunnels as well as sharp curves for access roads and a high incidence of crashes have proved a cause for concern. There are also concerns over current tunnel safety standards, which the original 1939 drive struggles to meet.
The environmental review process now has to be followed, after which the design phase for the project will be carried out, taking at least three years. Construction will only then be able to proceed and is expected to take around three years to complete.
In the mean-time, improvements are being carried out to upgrade the lighting, to meet current safety requirements.
The original Allegheny Mountain Tunnel was built in the 19th century for a rail link. However, the rail line never opened and the tunnel was never used due to concerns over its safety. When the Pennsylvania Turnpike was built in the 1930s, the old tunnel was considered briefly for a stretch of the road link, but then quickly rejected as being unsuitable due to its narrow width and also over the safety concerns. It remains unused and abandoned, with entry strictly forbidden.
