The next stage in turning an old rail route into a leisure trail has been launched.

A planning application has been submitted to Bradford Council to transform the Thornton to Queensbury section of the Great Northern Railway into a path for cyclists, walkers and horse riders.

The project is expected to cost about £500,000 and is being spearheaded by Sustrans, the alternative transport group.

The route crosses magnificent Thornton viaduct, which the group hopes to have repaired by the summer.

The first phase of the Great Northern Trail, between Cullingworth and Harecroft, which crosses Cullingworth and Hewenden viaducts, was opened in May.

This week's announcement comes as an illustrated book, financed by the navvies who built the original railway, goes on show at Bingley Library.

The book was presented to Isaac Woodwish, the chief engineer, on completion of the line in the 1880s.

The exhibition has been organised by Great Northern Trail voluntary ranger Richard Kunz, a physiotherapist in Bingley. It will go on display for two weeks from Monday.

"This is a wonderful book and must have cost a fortune to produce," said Mr Kunz. "It has watercolour images of the various stages of the project and is illustrated with gold lettering."

The construction of the line was a massive feat of engineering requiring the construction of a number of viaducts, cuttings and tunnels.

It was built between 1874 and 1884, and mile for mile was the most heavily engineered railway in West Yorkshire.

Jeff McQuillan, the Great Northern Trail Forum chairman, said Thornton viaduct would be finished with a similar metalled surface to Cullingworth and Hewenden viaducts.

"There is a lot of hard work ahead but the prize will be a great asset to the community," said Mr McQuillan.

"Local people are urging us to build more of the trail, and this planning application demonstrates our determination to deliver all the route to secure the maximum benefit for the public."

Talks would be held with the nine landowners along the second phase four-kilometre route to agree access.

"We don't have to buy this land, just reach agreement. It is only a two-and-a-half-metre wide path," he added.

Money had been promised from the Railway Heritage Trust and other external funding would be sought.

Backing for the first phase had come from the European Fund, National Lottery, Countryside Agency and the Department of Transport.

The final third phase of the route will be the middle section, linking Harecroft with Thornton. It is more problematic because part of the old line is tunnelled.

The original line was closed to passenger traffic in 1955 and finally to goods trains in 1960.