It carries a suburban stopping passenger service from central London to Sevenoaks, and is also a relief route for the Chatham Main Line carrying passenger trains from London Victoria to the Kent coast.
Freight traffic includes aggregates trains to and from locations along the Thames estuary, and Kent, aviation fuel running between Colnbrook (for Heathrow) and the Isle of Grain, and a small number of international workings from the Channel Tunnel via the yard at Dollands Moor.
The five stations on the original route were: The length of the Catford Loop is nearly eight miles (12.5 km).
The line was electrified with the other SECR urban routes on 12 July 1925 by the Southern Railway on its 660 DC third-rail system.
All other services originate from London Blackfriars and Thameslink Core and call at all stations.