Third weekend of rail disruption on London Midland
Passengers are being warned for a third time not to travel on London Midland trains on Sunday, unless essential, due to a drivers' pay dispute.
Employees are refusing to work overtime, which has led to a shortage of drivers.
The Birmingham-based firm said it was expecting severe disruption, with only three routes operating.
The service operates throughout the Midlands connecting to London and to the North West.
A statement on London Midland website said: "Unfortunately, due to an agreement relating to drivers working overtime not being renewed by Aslef (the train drivers' union), we are currently having to cancel a number of trains each day."
A spokesman for Aslef apologised for the disruption.
In 2009 London Midland offered drivers double time to work on Sundays but has recently dropped the rate.
Aslef has said its members were "extremely angry."
Services were disrupted by the dispute on 11 and 17 March.
The routes in operation on Sunday are Milton Keynes to London Euston, Blake Street to Redditch (via Birmingham) and Stourbridge Town to Stourbridge Junction.
Road transport will be available between Lichfield and Blake Street, Northampton and Rugby and Northampton and Milton Keynes, a spokesman confirmed.
The train firm operates through London, Hertfordshire, Buckinghamshire, Bedfordshire, Northamptonshire, Warwickshire, Staffordshire, Herefordshire, Worcestershire, the West Midlands, Shropshire, Cheshire and Merseyside.