Thackley Tunnel

In 1968, the southern tunnel was closed, coinciding with the closure of the Great Northern Branch Line from Shipley to Laisterdyke via Idle and Thackley.

[3] The 9.5 miles (15.3 km) direct route posed difficulties particularly with steep gradients; one towards the western section of the line where a stationary steam engine could have had to have been used to assist trains in the ascent of a 1:30 incline.

[3] Robert Stephenson was consulted from an early stage and surveyed a new route along the Aire Valley to enter Bradford from the north.

He explained to the parliamentary committee that the revised line's ruling gradient of 1:200 would be more suited to the low-powered locomotives available and journeys would be quicker and cheaper than by the direct route.

At Thackley Hill seven shafts which reached depths of up to 252 feet (77 m) were started under the direction of engineer Francis Mortimer Young.

A condensing steam engine, generating up to 25HP, was installed for lowering men and equipment into the shafts and raised spoil.

[3] The workforce was praised by Hudson, who spoke of their energy and spirit during a celebratory meal marking the tunnel's completion after sixteen months.

[3] In July 1897, increasing levels of traffic using the line led to Midland Railway deciding that a second bore was needed.

In April 1985, a bulge was detected at the haunch closest to the live tunnel; steps to address it included installing steel ribs to brace the area and additional monitoring.