A fault with the signalling system between Castle Cary and Taunton means trains have to run at a reduced speed on the line towards Taunton.
Trains running between these stations may be delayed by up to 20 minutes or diverted via Bristol Temple Meads.
Disruption is expected until 17:00.
Check before you travel:
You can check your journey using the National Rail Enquiries real-time Journey Planner.
Compensation:
You may be entitled to compensation if you experience a delay in completing your journey today. Please keep your train ticket and make a note of your journey, as both will be required to support any claim.