A tweet from Sutton police said: "Brighton Road outside Sutton railway station. Road still shut as traffic officers investigate life changing accident pedestrian knocked over."
A Metropolitan Police spokesman said: "Police were called at approximately 2.30pm today to a road traffic collision on Brighton Road, Sutton, between a pedestrian and a car.
"The pedestrian, a 70-year-old woman, was taken to a south London Hospital by London Ambulance Service.