It runs north-south between Todmorden and Littleborough. The tunnel is just over 1.6 miles (2.6 km) long and carries two standard-gauge tracks in a single tube.
The tunnel was mined by hand through clay, then lined with bricks. It was aligned by drilling fourteen vertical shafts to provide survey points on the hillside above: after the tunnel was completed these were used as blast relief shafts to vent steam from locomotives passing through.
Despite its age, the tunnel has been continuously used for passenger and freight since it opened, with one exception: it closed for the first eight months of 1985 following a serious fire. This Summit tunnel fire may have been the biggest underground fire in transportation history.
Opened on November 30, 1867, after two years of blasting, the 1,659 foot long SummitTunnel (#6) at Donner Pass was used continuously for 130 years by the trains of the Central Pacific, Southern Pacific, Union Pacific, and AMTRAK.
Originally a tunnel (#7), the SP removed its top at some point only to discover that it needed to be covered again to keep the tracks clear of snow.
The tunnels and walls were built with Chinese labor, as was most of the CPRR.
The Wrights tunnel is an abandoned railroad tunnel that crosses the San Andreas fault in the southern Santa Cruz Mountains in the vicinity of the 1989 Loma Prieta earthquake, that was damaged and deformed during the 1906 earthquake.
This indicates that in 1906 the Summit Ridge fractures were a surficial phenomenon, not a reflection of tectonic faulting.
No large fractures occurred across Summit Road near the intersection of Loma Prieta Avenue in 1989, nor was any fracture in the immediate vicinity this large (the photographs and reports suggest about 1 m of vertical displacement, and several decimeters of extension in 1906).
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