Moves to improve the Cotswold Line rail route between Oxford and Worcester took a step forward today, when Network Rail indicated its preferred option for the project.

This would see double track reinstated for four miles from Finstock, near Charlbury, to Ascott-under-Wychwood, and on the 16-mile section from Moreton-in-Marsh, in Gloucestershire, to Evesham, in Worcestershire.

If the scheme gets the go-ahead, the only remaining single-track sections on the line would be for 10 miles from Wolvercote junction, north of Oxford, to Finstock, and from Evesham to Norton junction, on the outskirts of Worcester.

After a £150,000 year-long feasibility study, Network Rail has included the project in its updated Strategic Business Plan, which was submitted to the Office of Rail Regulation today.

The plan says that the improvements, which are estimated to cost between £74m and £92m, could allow up to four trains an hour on the line, instead of the current two, improve reliability and reduce journey times by up to four minutes by using new high-speed points at the start of the single-track sections.

Although the redoubling scheme is not among the improvement projects the Government has indicated it is prepared to fund from 2009-14, the rail infrastructure firm is understood to believe it has a strong business case for the plan and can show it has wider benefits for the route between London, Reading, Didcot and Oxford.

The ORR is expected to give its verdict in June.

Knock-on delays caused by services from the Cotswold Line often affect services on other routes, with the long single-track sections to blame for the problems.

In January, First Great Western's Thames Valley route director Mike Carroll told Charlbury commuters that the Cotswold Line had the worst punctuality record on the firm's entire network, though there have been signs of improved performance in recent weeks.

The Cotswold Line Promotion Group, which represents passengers on the route, has campaigned for 30 years for the reinstatement of double track, which was removed from much of the route in 1971.

Andrew Wilkins, from Long Hanborough, is the CLPG's treasurer. He welcomed the news and said: "We would say this is a step in the right direction. Improved infrastructure is the only way to get over the current reliability problems.

"There are too many trains using the single line and when something goes wrong, we know what the consequences will be.

"Reducing the length of single track in Oxfordshire could significantly reduce delays to trains which are held up at Wolvercote and Ascott-under-Wychwood."

A Network Rail spokesman said: "We are already working hard with First Great Western to push up performance and we believe that the Cotswold Line project offers good value for money and would meet the objectives of improving both performance and capacity.

"While not part of our core funding requirements, we have put a strong case to the ORR to seek additional funding for this worthwhile project."