Rail services between East Anglia and London will be cut by work in south Essex for the first two weekends in May.
Engineering work between Chelmsford and London will mean trains from Suffolk, Norfolk and north Essex will stop at Witham from where passengers will be taken by bus to Newbury Park tube station on the Central Line.
Some trains will continue to Chelmsford for people visiting that city.
The closures will apply over the first bank holiday weekend from May 1-3 and on the following weekend May 8-9 - and will see a number of projects completed in the area.
Jamie Burles, Greater Anglia managing director, said: “These projects will help to improve punctuality and performance along these vital parts of our network.
“We will be running a rail replacement bus service while the work takes place, so customers will be able to complete their journeys. Passengers should check before they travel, allow more time for their journey and wear a face covering when travelling by train or rail replacement bus and at our stations."
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