Twitter is being used by First Capital Connect trains to alert London commuters to possible delays on some routes.
Commuters simply have to "follow" First Capital Connect.
Users can specify the routes and times they are interested in to receive free alerts on that service in and out of London
According to First Capital Connect, the service can be suspended and reinstated easily by sending either the word "stop" or "start" in a direct message.
The Twitter service covers routes to and from London Bridge, King's Cross and St Pancras.