The delayed works on the Preston to Manchester route will necessitate another closure, this time for a nine-day period over the summer, Network Rail has announced.
The upgrade works will continue until November 4, with primarily overnight and weekend works.
However the line will be totally closed from Saturday, August 25 to Sunday, September 2. A replacement bus service will run on these days.
Martin Frobisher, managing director for Network Rail’s London and North Western route, said: “Our Manchester-Preston upgrade is part of the Great North Rail Project, the rail industry’s team effort to transform train travel for customers across the North through track and train improvements.
“I’m sorry for the further short-term disruption that this work will cause, but please don’t lose sight of the long-term improvements which will be delivered. In future electric-powered, greener, faster, more frequent, more spacious, more reliable trains will become the norm through the Bolton corridor.
“We recognise the May timetable change resulted in poorer service for many customers than it should have done. We are working together with our train company partners to resolve current issues as soon as possible.”
In early January Network Rail announced delays to its May 2018 deadline to complete its Preston-Manchester upgrade.
This was caused by unforeseen poor ground conditions hampering engineers’ progress installing foundations for masts to carrying overhead power lines.
Delays to progress were compounded by the collapse of Carillion, the lead contractor for the scheme.