Due to greasy rails on the line going up from Ingrow East railway station, a train could take almost ten minutes to clear Lees Moor Tunnel.

After closure, the tunnel at Lees Moor was used by British Rail and staff from St Bartholomew's Hospital in London to test for smoke emissions from both diesel and steam locomotives.

The tests were in relation to cancer and the inside of the tunnel and the lack of ventilation shafts helped to keep the smoke lingering for advanced measuring.

[12] The lines around Cullingworth, including those through Lees Moor Tunnel, were also used for brake testing on Diesel Multiple Units that were then being deployed by British Rail.

The roof of the tunnel had to be lined with polythene sheeting as no ventilation shafts were present in the construction resulting in a heavy moisture atmosphere.