Network Rail video
Network Rail and Arriva Trains Wales say the new Loughor Viaduct will carry improved train services to West Wales.
It will carry two tracks between Swansea and Llanelli instead of the previous one.
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All calm and quiet overnight, but southern areas could be in for a surprise tomorrow!
Scottish people living in Wales have been giving ITV News their opinions about the Scottish referendum vote on Friday.
While the campaign trail in Scotland has hotted up today, in Wales businesses are keeping a close eye on tomorrow's decision.