Stations along the Ebbw Valley line include Newbridge, Crosskeys and Risca and Pontymister.
The replacement of the bridge will take place in September, with the railway closed on three separate occasions:
12.50am on September 4 to 5.40am on September 7
12.50am on September 12 to 5.40am on September 14
12.50am on September 19 to 5.35am on September 28.
A replacement bus service will be available on these dates to transport passengers between Ebbw Vale and Newbridge stations.
Traffic management has been put in place until October 18.
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