Network Rail today announced moves aimed at working more closely with rail operators under a "deep alliance" with one of the UK's biggest train firms.
Officials said a single, senior joint management team could be established between NR and South West trains to look after train and track on the route out of London's Waterloo station.
NR has already announced plans to form alliances with a number of rail operators, saying they would cut costs and deliver a more "passenger focused" operation.
But today's move signals a more integrated way of working and is seen by some observers as the biggest step towards integrating the running of track and trains since the two roles were split when British Rail was privatised in the 1990s.
NR chief executive David Higgins said: "Working more closely with the train operators, with decision-making devolved to the front-line and better aligned incentives, will, I believe, bring substantial benefits.
"The alliances will deliver a better service for passengers and freight users and at lower overall cost to the taxpayer."
NR said the alliances formed part of the "substantial" changes under way within the rail industry as it pushes decision making and accountability from its headquarters to its 10 geographic operating regions and encourages much closer collaboration with train operators to speed up improvements for passengers and freight users.
Tim Shoveller, managing director of South West Trains, said: "We operate one of the busiest commuter rail networks in Europe and we have a real opportunity to build on the close partnership working we already have in place with Network Rail. Our joint proposals for a deep alliance have the potential to deliver a better service for our passengers, ensure faster and more customer-focused decisions, give better value for money to taxpayers and create a more efficient railway for the long-term."
Charles Horton, managing director of Southeastern, one of the operators which has made an "alliance agreement" with NR, said: "We have always had a close working relationship with Network Rail and have developed innovative projects together in the past, such as installing anti-ice tanks on passenger trains and setting up an integrated control room.
"This new alliance is the next logical step and will serve to formalise our existing close relationship. It will help us continue to improve the railway's performance for passengers and help drive efficiencies across Southeastern and Network Rail."
Manuel Cortes, leader of the Transport Salaried Staffs Association, said: "The Tories made a huge mistake when they broke up British Rail into 100 different pieces 15 years ago and separated track and train management, the only country in Europe to do adopt such a bizarre policy.
"By joining up track and train again in only one region, they are making a dog's breakfast of what should be one unified industry, not a collection of jigsaw pieces owned by different private companies.
"Everywhere in Europe, there is one publicly-owned rail network in each country. We should have the same here instead of having the most overcrowded and most expensive network in the Western world."