Its engineers have been carrying out work on several bridges in the Leicestershire area over the past two weekends, in order to provide space for overhead line equipment. This will enable the powering of new bi-mode trains on the route.
Engineers also replaced a large section of track and carried out preparation work as part of upgrades to the Midland Main Line.
It now plans further upgrade work, lowering sections of track and continuing to work on the bridges, and will have to close lines between Leicester and Kettering on Sundays for the rest of this month.
Rail replacement buses will operate between Kettering, Market Harborough and Leicester. Services will divert via the closed section, which will add extra time to journeys.
The Midland Main Line Upgrade project involves electrifying the line between London St Pancras and the East Midlands, which will enable bi-mode trains to run on the line, making train travel greener, faster and smoother.
In addition, work continues on the Midland Main Line on selected Sundays in November and December between Luton and Bedford. Engineers will be working to upgrade overhead line equipment to enable the new fleet of trains to run at speeds of up to 125mph.
Until 08.05 on the mornings of Sunday 26 November and 3 December, buses will replace Thameslink services between Luton and Bedford. A revised timetable will operate between London St Pancras and Luton.
Passengers are again being encouraged to check their journey before they travel via National Rail Enquiries or their train operator.
Gavin Crook, Principal Programme Sponsor for Network Rail's East Midlands Route, said: “Our teams have worked extremely hard over the past two weekends and great progress has been made as we continue to deliver the Midland Main Line Upgrade.
“We want to thank passengers for their patience whilst we complete this work and apologise for any disruption caused. We're urging passengers to check their journey before they travel via National Rail Enquiries or their train operator's website”.
Dave Meredith, Customer Services Director for EMR said: “An amended timetable will be in place on our Intercity route on Sunday 19 and Sunday 26 November. No trains will call at Market Harborough and journey times will be extended, so please allow extra time when travelling.
“Our Connect services will also start and terminate at Wellingborough, instead of Kettering or Corby.
“Rail replacement buses will run between Kettering, Market Harborough, and Leicester to keep our customers moving.
“We would like to thank our customers for their patience whilst the engineering work along the Midland Main Line is taking place.”