Lines between London and the east needs faster trains
Campaigners are calling for faster and more frequent rail services between Norwich, Cambridge and London.
Network Rail is replacing overhead power lines installed 30 years ago, reducing the number of delays and cancellations caused by faults.
Changes are also to be made at Ely where the junction has become a bottleneck, Network Rail said.
Campaign group Railfuture welcomed improvements but called for twice-hourly services to and from London.
Capacity has been increased at Liverpool Street, and Network Rail has pledged under its new plans to examine improvements to journey times.
Track will be renewed between Liverpool Street and Norwich, and a line-speed study is under way to examine further improvements to journey times.
The upgrade of outdated overhead power lines between London Liverpool Street and Chelmsford is set to be completed by May 2017.
The next step is to renew overhead line equipment on the branch line to Southend, which also dates to the 1950s.
A new rail operating centre (ROC) will open in Romford in 2014 and this will eventually control services in London, Essex, Suffolk, Norfolk, Cambridgeshire and Hertfordshire.
Network Rail said its aim was to cut the cost of running and maintaining the railway network in the east.
Campaign group Railfuture said this was being done by central control and cutting the number of signal boxes, as well as improved communications and other measures.
Speaking for the organisation Chris Burton said: "Services are better now than they have ever been. Passengers travel in the best coaches even though they are 30 years old and refurbished."