Network Rail is to examine the possibility of reopening a railway line which has been closed since 1969.
Campaigners have been pushing for the Uckfield to Lewes to be reopened.
A group called The Central Railway Corridor Board (CRCB) was set up last year to press for its reopening.
Network Rail has now signed a contract with East Sussex County Council agreeing to carry out an in-depth investigation into whether the line could be reopened.
CRCB chairman Rupert Simmons said: "This study is a thoroughly exciting prospect as there's a higher level of involvement from the rail industry than before and the desire for a definite outcome."
Lewes MP Norman Baker said: "I've campaigned for more than 20 years to reopen this line. To me it's a no-brainer.
"At the moment the Lewes to London line is at maximum capacity every rush hour. This would create an alternative route that might remove some of the pressure."
Duncan Bennett, councillor for Wealden Town Council, said: "A lot of people in Uckfield don't want to go to London, they want to go to coastal towns like Brighton, Eastbourne, Seaford and Newhaven either for work or for entertainment but at the moment they can't do that without having to travel in the wrong direction first.
"When the Uckfield to Lewes line was open it was the southbound route that was busiest yet that was the one that was closed down.
"We carried out a survey across the Wealden area and found 84 per cent of people wanted the line to be reopened and would use it if."
An East Sussex County Council spokesman said: "Network Rail has a proven track record of managing similar studies and is better placed than anyone to undertake this type of work."
Network Rail has appointed an external consultant, Mott MacDonald, to look into whether reopening the line is the best option or if alternative forms of transport such as light rail or bus connection between the two stations would be better.
The study will cost between £130,000 and £140,000 and district, parish and town councils along the railway route have agreed to contribute.
The results of the investigation will be published by June.
Coun Bennett said: "We're very much hoping Network Rail will come back with some positive answers. I'd be surprised if they said it wasn't possible but the biggest obstacle will be funding."
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