Campaigners are racing against the clock to improve Braintree rail links after a new station was given the go ahead.
Outline planning permission was granted last week for a new main line station at Beaulieu Park, Chelmsford, as part a £1 billion development.
The plans also include up to 3,600 homes, a new business park and a multi storey car park.
Rail users hope a £9.4 million rail loop can be built at White Notley Station to allow two trains per hour, rather than the current one, to travel to Braintree.
David Bigg, chairman of the Witham and Braintree Rail Users Association, said: “It is a race against the clock and we have got to beat it.
“It will have an adverse impact on the business case for the loop on the Braintree branch line.
“It is our view that they will build the houses first so therefore we will have quite a lot of congestion initially into Witham and Chelmsford.
“But once the [Beaulieu Park] station is in the business case for the Braintree loop will be seriously damaged.
“With additional parking, rumoured to be over 1,200 spaces, it is going to be a magnet.
“If we can get [funding] by 2017, which is five years away, I think we can still get it.”