GWR has issued a warning to passengers to check their journey before they travel ahead of the upcoming railway strikes.
Two further days of rail strikes are set to take place on Wednesday, February 1, and Friday, February 3, amid an ongoing industrial dispute between Network Rail, railway operators (including GWR), the RMT and ASLEF trade unions.
Next week will see another two days of strikes from the ASLEF trade union which represents train drivers and has led to a severely reduced service on a limited number of routes.
The only services running on the strike days will start later and finish earlier, starting between 7.30am and finishing approximately 7.30pm.
There will be a limited service between Plymouth and Gunnislake during those times.
However, there is set to be no services calling on the Cornish main line, affecting Liskeard railway station and Bodmin Parkway and all stations west, in addition to no services calling on the Liskeard to Looe line.
In addition, there will be no service between Okehampton and Exeter Central or Exeter St Davids on the strike days, potentially affecting the travel plans of commuters in the Bude and Holsworthy areas.
A spokesperson for Great Western Railway said: "If you intend to travel on these routes, please check before you travel. Trains that are operating will be busier than usual because we will not be able to offer the normal service frequency.
"Unlike previous strikes, the days in between strike days and immediately after the last strike day will be largely unaffected and GWR expects to be able to operate a full level of service, with some very minor alterations.
"Online journey planners have been updated with the latest timetable information, please see the passenger information table for details. Customers who have already purchased tickets for strike days can claim a full refund or amend their ticket; those who travel and are delayed may be entitled to Delay Repay compensation if they are delayed by 15 minutes or more.
"To help customers, tickets will be valid for travel on alternative days on GWR services as follows. Tickets for 1 and 3 February can be used the day before, or up to and including Tuesday 7 February.
"Season-ticket holders can apply for compensation through the Delay Repay scheme.Our Refund policy remains in place. If you hold a return ticket, you can claim a refund of your unused full fare, even if only one leg of your journey is affected."