Key rail upgrades for passengers travelling to London from Norfolk and Suffolk have been completed over Christmas and New Year.
Network Rail engineers installed more than 10km of overhead wire at Ilford as part of a £250m wiring system which automatically adapts to temperature changes.
The 37km stretch from Chelmsford to Ilford on the Norwich to London mainline now has the new wires installed.
Network Rail said the system will result in fewer delays and cancellations as speed restrictions will no longer need to be imposed between Chelmsford and Ilford in hot weather.
Work to install a further 8km of overhead wire on the section between Ilford and Manor Park begins at the end of the month.
Network Rail said the improvements will last for 'decades to come' and help to provide a more reliable service to the growing numbers of passengers using the busy mainline.
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