Weekend train travellers to London face almost a year of disruption as rail chiefs embark on a £150m upgrade of the line.

Weekend train travellers to London face almost a year of disruption as rail chiefs embark on a £150m upgrade of the line.

Passengers heading for Liverpool Street will have to take the bus into the capital from Ingatestone in Essex as overhead cables are rewired. Some Norfolk passengers are advised to travel via Cambridge to avoid switching to a bus.

Network Rail said the upgrades were a priority, but it is believed that the work was brought forward after lobbying from rail firm National Express, and the project is an attempt to reverse years of underinvestment and delays which have tested travellers' patience.

After Christmas, work will take place on Sundays on stretches of the line between Shenfield and Stratford for 40 weeks.

The work comes as a survey estimates the cost of congestion to Britain's businesses is £23.2bn - up from £5.7bn from last year.

Peter Lawrence, national president of rail travellers' group Railfuture, said: "In the longer term it will be good for us, but this can be traced to underinvestment over the years. It's not pleasant if there is major work to be done and it will affect passengers, but weekends are the lighter time to do it."

Chris Starkie, chief executive of Shaping Norfolk's Future, which is carrying out a survey of train users, said: "We know that the stretch between Shenfield and Stratford is out of date and unable to cope with the volume of traffic. Any work to improve the line will be painful as the work needed is far more than a cosmetic patch-up.

"Passengers will be willing to put up with this disruption, assuming it really does improve reliability."

A spokesman for Network Rail said the work would take place on 40 occasions - part of a four-year project to upgrade the network.

"Much of the work we are doing in 2009 is along the Great Eastern Mainline (GEML), but there are some enhancements taking place on branch lines," he said. "There will be a continuation of the major overhead line equipment rewiring project on Sundays between Stratford and Shenfield. Local routes in East Anglia will remain largely unaffected. Work is publicised widely in advance so passengers have the opportunity to make alternative travel arrangements."

Jill Casswell, National Express spokesman, said the firm would try to ensure journey disruption was kept to a minimum.

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