Network Rail says it is reducing the number of delays caused by engineering works by using a new ballast-laying train.
The 'high output ballast cleaner' travels along a stretch of track and replaces old ballast with new while other lines can remain open.
Ballast needs replacing on the line every 25 years as it gets ground down into smaller stones.
Network Rail is spending £170 million on upgrading the mainline between Norwich and London
It's already replaced ballast on 13 miles between Norwich and Ipswich and on Monday 18th May it will start work between Colchester and Shenfield until mid-October.
It does mean there will be some changes to the timetable
There will be fewer trains after 20.30 on Monday, Tuesday and Wednesday and on some Sunday mornings.
Although the number of seats available will remain the same the journey may take a little longer. The advice to passengers is to check times with Abellio Greater Anglia before travelling.