St Albans Abbey services are unable to run on the train line this morning.
The problem is caused by a broken-down carriage on the shuttle service between Watford Junction and St Albans Abbey station.
It is not expected to be clear until midday and commuters are advised to use the replacement bus.
Tickets can be also used on Arriva 321 buses.
This follows delays on the same route on Tuesday, February 6, which were caused by a faulty train.
For more information, visit www.nationalrail.co.uk/service_disruptions/183681.aspx
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