There's a replacement bus service running on Arriva Trains Wales between Harlech and Pwllheli.
Delays of up to one hour on Arriva Trains Wales between Newport and Hereford are expected due to broken down train at Abergavenny.
There is no estimate for when a normal service will resume.
There's a replacement bus service running on Arriva Trains Wales services between Milford Haven and Haverfordwest because of a derailment at Milford Haven.
There's a replacement bus service running on Arriva Trains Wales between Milford Haven and Haverfordwest after a derailment at Milford Haven.
There are delays of up to 30 minutes on Arriva Trains Wales services between Newport and Cheltenham Spa because of a signalling problem at Gloucester.
There's a revised service on Arriva Trains Wales between Machynlleth and Pwllheli because of an unsafe electricity pylon at Afon Crigyll.
Early morning and evening train services on the Cambrian Coast Line between Harlech and Porthmadog will be suspended from tomorrow morning for emergency repairs to an unsafe pylon located near the railway in Llandecwyn,Gwynedd.
Day time services, including school train services are not expected to be affected by the repair work, though they may be subject to last minute delays or cancelations.
A spokesperson from Arriva Trains Wales said replacement bus services will be operating and they are "making every effort" to minimise the disruption to the service.
There are delays of up to 20 minutes on Arriva Trains Wales at Cardiff Queen Street because of a problem with line-side equipment.
A Welsh Assembly committee has begun accepting feedback ahead of an official inquiry into the future of the Wales and Border rail franchise.
The current service is run by Arriva Trains Wales and its 15-year contract runs out in 2018.
Before then, Cardiff Bay politicians will look at whether the current franchise meets passenger needs and what improvements are needed for the next franchise.
Normal service has resumed on Arriva Trains Wales between Welshpool and Shrewsbury after earlier over running engineering works at Shrewsbury.