Train disruption in West Cornwall will continue until Saturday, says GWR, with valid rail tickets accepted on rail replacement buses.
Services are not running west of Truro, with the branch line between St Erth and St Ives also out of action.
Passengers travelling between St Erth and Penzance and St Erth and St Ives should use local bus services 17 and 17A.
The disruption is due to engineering work and, says GWR, may also affect some service between Truro and Plymouth.
