One of the region's main rail lines returns to normal on Monday after a day of engineering works.
Buses replaced trains south of Stevenage on the East Coast Mainline on Sunday, causing travel disruption.
However, train operator One says the line linking London with Norfolk, Suffolk and Essex is still closed at Chelmsford. A bus shuttle is operating.
And services through Ely are subject to delays because of work on the lines to Cambridge and Peterborough.
Services between Norwich and Cambridge, Ipswich and Peterborough and King's Lynn and London are also affected.
These delays will continue until Wednesday.
A spokesman for One apologised for the inconvenience and advised customers to check train running times before travelling.