High Quality Content by WIKIPEDIA articles! The Hindhead Tunnel is a road tunnel that opened (southbound and northbound) on 29 July 2011 as part of the new Hindhead bypass for the A3 road in Surrey. It forms part of the 4 mile (6.7 km)dual-carriageway being built to replace the last remaining stretch of single-carriageway on the 68-mile (109 km) London to Portsmouth road. The bypass is intended to improve road safety, reduce congestion and improve air quality. At 1.2 miles (1.83 km) long, the tunnel is the longest non-estuarial road tunnel in the United Kingdom, and takes the road beneath the Devil`s Punch Bowl, a Site of Special Scientific Interest.