A road will close on Monday for more than five months as work is carried out to improve the railway.
As part of a £400m electrification programme, several bridges are being rebuilt to allow overhead electricity lines to run underneath to power trains.
Harpers Lane, in Chorley, will be shut until October 24, while Railway Road, Adlington, will also be closed from June 9 to
Network Rail said diversions would be clearly signposted and that residents and businesses close to the affected bridges were being written to about the closures.
The work is designed to improve rail connections between Manchester and Preston via Bolton.
Ian Joslin, area director for Network Rail, said: “I apologise for any inconvenience caused and thank local people for their patience while we complete these essential upgrades.”