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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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The heavy showers will ease during the first part of tonight, leaving a dry night with mist in places.
A 1950s pin-up girl from the Vale of Glamorgan has returned to the spot where she won the nation's hearts.
The band play the Liberty Stadium on Saturday night as part of their 'Everything Must Go' 20th anniversary tour.