Due to open next year, the 45-kilometre Regional Rail Link between Southern Cross Station and west Werribee is the state's biggest rail project since the City Loop was built in the 1970s. It will separate Metro and V/Line trains, giving each operator its own dedicated tracks through Melbourne's west and removing rail bottlenecks that cause delays.

But cuts made to the project plans a few months before Labor lost the 2010 state election have compromised that outcome, leaving metropolitan and regional tracks to intersect at a key junction just north of Sunshine station.

The change in plans means Metro's Sunbury-line trains will continue to cross paths with V/Line's Bendigo and Ballarat-line trains

when the Regional Rail Link opens, leaving intact a pinch point that can create train delays. It had been planned to remove the junction by building a rail-over-rail flyover.

Details of the ''reduction in the originally proposed scope'' of the Regional Rail Link are revealed in documents released to Fairfax Media under freedom-of-information laws. Other planned parts of the project that were cut include removal of three level crossings on the Ballarat line that will form part of the Regional Rail Link between Sunshine and Deer Park; enhancement of the primitive V/Line stations at Deer Park and Ardeer; and building a second pair of tracks between Deer Park and Sunshine stations.

The documents reveal the Regional Rail Link Authority made the cuts ''in order to meet the project objectives and comply with the funding agreement with the Commonwealth''. The federal government is contributing $3.2 billion and the Victorian government $1.6 billion to the project.

Authority spokesman Bob Neilson said work done in 2010 identified that money could be saved by removing several parts of the project that were not essential to achieving its aims.

Mr Neilson said the junction would be the only point of conflict between Metro and V/Line trains when the new line opens, and that the level of train traffic there would be light enough to create a timetable that would prevent it from becoming a regular source of delays for passengers.

But he conceded there was potential for delays at the junction if a train were already running behind time when it got there, and that the scrapped works would have to be completed in future years to deliver increased services to Melton.

''A rail-rail grade separation in Sunshine is not necessary for Regional Rail Link,'' Mr Neilson said. ''However, an increase in services as part of any future project may mean a grade separation is required.''

A rail engineer familiar with the cuts to the project said the decisions made, including not to remove level crossings at Robinsons Road, Derrimut Road and Fitzgerald Road, would add ''well over half a billion dollars'' to the eventual cost of duplicating and electrifying the line to Melton, where the population is forecast to grow by 117,000 in the next 25 years.

Melton station is already used by more than 2000 passengers a day, and V/Line has identified the duplication and electrification of the largely single-track Melton railway line as one of the key works needed beyond this year, proposing in its 2012 strategic operations plan that it should happen by 2018.

Read more: http://www.theage.com.au/victoria/cutbacks-compromise-5b-regional-rail-link-20140330-35rx6.html#ixzz2xUICnhC0