Rush hour commuters are being asked not to get on the Northern Line between Tooting Bec and Clapham North - because TfL say it's just too busy.
The pilot project, which starts on Monday, will see TfL offering advice on alternative routes and asking commuters to walk or cycle instead of boarding trains on the line between 0800 and 0845 on weekday mornings.
The scheme follows similar tactics adopted during the Olympics to reduce overcrowding.
More top news
Chelsea won the first domestic trophy of the season thanks to a 2-0 win over London rivals Spurs at Wembley.
An online video showing a naked man apparently falling down the outside of Buckingham Palace has split opinion online - is it a hoax?
A new market has started up in London championing the production of sustainably produced, local food.