Trains to and from Lancashire on the West Coast Main Line will be disrupted over a fortnight this summer.
It will mean that some services will not run, or be diverted.
Between July 20 and August 4, Network Rail engineers will be working to upgrade track, cabling, overhead lines and signalling on the busy Acton Grange junction near Warrington.
Acton Grange is a key section of the West Coast Main Line between Crewe and Preston.
It helps connect Chester and Warrington to Manchester in the east and Wigan, Preston, the Lake District and Scotland to the West Midlands and London.
It is used by more than 260 trains every day.
A total of £27m is being invested, as part of the Great North Rail Project, to bring the outdated West Coast Main Line track and equipment to modern standards and improve reliability.
Network Rail said: “While the work takes place, many trains will be diverted to keep passengers moving.
“In some cases, passengers may need to change onto a different train or a bus for a section of their journey.”
Passengers are being urged to check before they travel and to allow more time for their journeys as services will be busier than usual.”
Some preparatory works will also take place over the upcoming May bank holiday.
Direct services between Preston and London Euston will run, diverted between Wigan and Crewe, via Manchester Piccadilly.
Services between Preston and London Euston via Birmingham will terminate at Preston (for trains south) and Crewe (for trains north). Passengers travelling to / from Birmingham are advised to take a rail replacement bus service between Preston and Crewe to pick up connecting trains.
Services between Blackpool and London Euston will not run.
Passengers are advised to travel to Preston for a connecting train to/from London.