– Gareth Powell - TfL director of strategy and service development
"During the 2012 Games many of our passengers made small changes to their journeys which meant we were able to carry record numbers without the transport network feeling any busier.
"This section of the Northern Line is exceptionally busy during part of the morning and while the modernisation of the line will help to relieve crowding when complete next year this trial will look at whether we can improve the situation now.
"By making a small change to the time they travel our passengers' journeys could be faster and more comfortable."
TfL are asking commuters not to use the Northern Line during rush hour mornings between Tooting Bec and Clapham North - because the service is too busy to cope