Dartford Loop Line

The Dartford Loop Line is one of three lines linking London with Dartford in Kent, England. It lies to the south of the other two: the North Kent Line (or Woolwich Line) and the Bexleyheath Line.
Informally, the line is known as the Sidcup Line in the context of Southeastern Metro services.
History.
In June 1862 the South Eastern Railway obtained powers for a second line between London and Dartford from a junction with the main line at Hither Green to its existing North Kent line to reduce congestion on the existing line and to give a more direct route between London and Dartford. This was to be routed via the town of Sidcup.
The Dartford Loop Line opened on 1 September 1866. A loop line in railway terminology is a line which leaves the main line at one location, and then rejoins in another place. The line initially had only five new stations: Lee, Eltham (now Mottingham), Sidcup, Bexley and Crayford. The station at Hither Green, near Lewisham, where the line deviates from the main line, was built after the opening of the third North Kent route, the Bexleyheath Line in 1895.
Pope Street, now New Eltham station, opened in 1878 between Eltham and Sidcup stations. Hither Green finally opened in 1895 serving both the Dartford Loop Line and the main line via Tonbridge. The final station to open was Albany Park in 1935. The Loop Line originally passed through mainly open country and farm land but it stimulated development around the new stations.
In 1899 the Lee Spur, a double track link between the up line of the Dartford Loop Line and the Hither Green marshalling yard, was built. The spur is occasionally used by freight and engineering work trains.
The Loop Line was electrified by the Southern Railway in 1926 along with the two other lines to Dartford.
In 1942 a double-track loop (the ‘Dartford Loop’) came into operation between the North Kent and Dartford Loop Lines, creating a triangular junction. This allowed direct running between the two routes, avoiding the need for a reversing manoeuvre at Dartford.
In 1955 the platforms on all Loop Line stations were extended to accommodate ten-coach trains, whilst continuing standard operation of eight-car trains. Most stations had goods yards which closed during the 1960s and were converted into car parks.
In the late 1960s the Dartford Loop Line along with the two other North Kent routes were re-signalled which saw the replacement of semaphores with colour light signals. In November 1970 most of the mechanical signal boxes on the line closed. In the mid-late 2000s the Dartford Area Resignalling Scheme saw the line resignalled.
Infrastructure.
The line is double track throughout and electrified at 750 V DC third rail.
Stations.
The line is a little over in length. The following are the stations served:
Future plans.
The line was due to be served by Thameslink trains following the completion of the first phase of the Thameslink Programme. The 2008 Network Rail Route Utilisation Strategy, however, made clear that consideration of running Thameslink trains to Dartford by any route had been abandoned due to timetabling and pathing difficulties.
Service patterns.
Train services are operated by Southeastern. All services run to London Charing Cross or London Cannon Street. 
The Monday-Saturday off-peak service is:
The Sunday service is:
The Sidcup Line is a freight route for trains to Kent. Most services use the Lewisham flyover via .
Rolling stock.
Rolling stock used on the line is Class 465 and Class 466 'Networkers' and Class 376 Suburban Electrostars.
Accidents.
On 11 October 1977, the derailed wagons of an eastbound coal train were struck by a Northfleet to Dunstable cement train between Lee and Mottingham. The locomotive ended up at the bottom of a garden of a house in Mottingham. There were no serious human injuries but several caged budgerigars in the garden were killed.
On 4 February 1997, an EWS freight train derailed near Bexley station (the Bexley derailment).