London to Aylesbury Line

The London to Aylesbury Line is the main railway line between London (Marylebone) and Aylesbury, going via the Chiltern Hills; it is operated by Chiltern Railways. The line includes the only route where National Rail trains use track that is utilized by London Underground services. This section is approximately 20 miles (the total mileage of the passenger section of the line is about 39 miles, meaning over 50% of the line is owned by LUL) between Harrow on the Hill and Mantles Wood, just north of Amersham.

The line operates modified timetables during autumn, as trains need to take more time to brake due to the leaves that fall on the line in the heavily wooded section between Amersham and Rickmansworth.

The line is part of the former trunk route, the Great Central Main Line.

History
The route towards Aylesbury opened in stages between 1868 and 1899:


 * 1) The Metropolitan & St. John’s Wood Railway (later part of the Metropolitan Railway) opened from Baker Street to Swiss Cottage in 1868.
 * 2) The Aylesbury and Buckingham Railway connected Verney Junction with Aylesbury in 1868. The route would become part of the Met in 1891.
 * 3) In 1879 the Met was extended from Swiss Cottage to Willesden Green.
 * 4) In 1880 to Harrow-on-the-Hill.
 * 5) In 1885 to Pinner.
 * 6) In 1887 to Rickmansworth.
 * 7) In 1889 to Chesham.
 * 8) Then in September 1892 the Metropolitan connected to Aylesbury via Amersham, making the Chesham route a branch line.

The Great Central Railway (GCR) decided to build a main line called the London Extension from Annesley Junction north of Nottingham to London via the Metropolitan Railway. It was the last main line to be built in Britain until High Speed 1. The line was completed in 1899. In 1903 the line between Harrow and Canfield Place (near Finchley Road) was built, thus bypassing this part of the Metropolitan tracks. The route was a major trunk route with many prestigious trains, such as The Master Cutler and The South Yorkshireman.

The line beyond Aylesbury Vale Parkway is currently closed to almost all passenger services: the service to Verney Junction was withdrawn in 1936 as London Transport wanted to focus more closely on London. The permanent way is now lost.

The line NW from Harrow was electrified in stages. In 1925, four rail electrification reached Rickmansworth and Watford, and the Metropolitan Railway planned to electrify the line as far as Aylesbury by 1935. However when the Met was absorbed into LT the plans were put on hold. Electrification of the final leg of the Met finally got under way in the late 1950s, but LT decided later to electrify only up to Amersham. The original intention to electrify further is evidenced by the colour light signalling which was fully installed as far as Aylesbury and by platform extensions up to Stoke Mandeville. In 1961 LT withdrew the Metropolitan Line from Aylesbury and since then it goes only as far as Amersham.

The mainline services to the North were withdrawn in 1966 as the Great Central Main Line was seen by Dr Beeching as a duplicate of the Midland Main Line. Now only freight services to Calvert and specials to and from Quainton run (the specials only run on certain Bank Holidays). The track remains in situ from Calvert west to Bicester Town and intermittently east to Bletchley.

Intercity 125 trains were used on the line, albeit rarely, during the 1980s. Also in the 1980s, there were passenger specials north to Milton Keynes from Marylebone via Aylesbury and High Wycombe, which picked up passengers at Quainton Road and the disused Winslow railway station.

On 14 December 2008, Chiltern Railways opened a new station, Aylesbury Vale Parkway. This station is situated two miles NW of Aylesbury station. A through service via Bicester to Oxford is under study.

Route description
From Marylebone the line runs through a series of tunnels as far as Finchley Road, from where the line runs overground and runs parallel to the Metropolitan and Jubilee Lines. A passenger on a train departing from Marylebone can see the Metropolitan Line just before the train enters the first tunnel, because the tunnels used by these two lines run only a few yards apart. At Neasden Junction, the Chiltern Main Line diverges to the west, while the Aylesbury line continues north parallel to the underground lines, passing Wembley Stadium.

The line then joins the Metropolitan Line tracks a few yards south of Harrow-on-the-Hill station and shares this track with the London Underground's fast Metropolitan Line services to Amersham from London Baker Street. This section runs parallel to the slow Met Line to Northwood and Watford. The line goes under the M25 north of Rickmansworth. At Chalfont & Latimer station, the Chesham branch diverges and Amersham is the final Metropolitan Line stop.

After Amersham, the line returns to Network Rail control and runs north to Aylesbury, running parallel to the A413 road for the majority of this section. At Aylesbury, the Princes Risborough line joins and this is where major maintenance work on trains is carried out. Beyond Aylesbury, the line is single track. North of Aylesbury Vale Parkway it is freight only, and runs through Quainton Road railway station to Calvert, where there is a waste depot. Beyond Calvert, there is a junction; one line goes east and joins the Varsity Line, while the main line goes north and becomes the dismantled Great Central Main Line.

Because of its route through the Chiltern Hills and perhaps due to lack of overall planning, having been built in stages, the line has some steep gradients and harsh curves. This is one of the main reasons why the GCR built a new line (the Chiltern Main Line) to Woodford Halse in 1906.



Towns/villages served
The line serves the following stations:


 * London Marylebone
 * Harrow on the Hill
 * Rickmansworth
 * Chorleywood
 * Chalfont and Latimer
 * Amersham
 * Great Missenden
 * Wendover
 * Stoke Mandeville
 * Aylesbury
 * (Quainton)

Operation
Passenger services are provided by Chiltern Railways. From Marylebone to Neasden Junction the track is shared with the Chiltern Main Line, and from Harrow to Amersham the track is shared with London Underground's Metropolitan Line, and is used by their "fast" services. As a result, all Chiltern trains must be fitted with the tripcock braking system to run on Underground lines. Marylebone Signalling Control Centre controls all the signals on the line between Marylebone and south of Harrow, and also from north of Amersham to Aylesbury. Marylebone can see all train movements throughout the line but does not control the signals on the Metropolitan Line section. These are operated by London Underground signal cabins at Harrow, Rickmansworth and Amersham. The Network Rail-controlled section of the line is fully equipped with ATP, the only line in Britain to have this bar the Chiltern Main Line and the Great Western Main Line. As a result all Chiltern trains must be equipped with ATP equipment.

Marylebone to Harrow on the Hill
After departing Marylebone, the speed limit rises to 50 mph for Sprinter-class multiple unit trains (of which the Class 165s and Class 168s are qualifying derivatives) and 30 mph for all other types of train. Beyond Canfield Place, near Finchley Road, the line speed remains at 30/50 until a point near Willesden Green, where the line speed for Sprinter-class trains rises to 60 mph. The line speed remains 30/60 as far as Neasden Junction, where the Chiltern Main Line diverges to the west. Passing Neasden, the line speed rises to 30/75 as far north of Northwick Park where the speed drops to 30/60 mph. Shortly after this, the line speed drops to 40 mph for all trains as the line enters London Underground control. The drop is due to the curve at Harrow.

Harrow on the Hill to Amersham
The line speed stays at 40 mph through Harrow until after the junctions north of Harrow. At this point the line speed increases to 60 mph as it runs parallel to the Metropolitan slow lines to Watford (this is the maximum limit on the London Underground section of the line). The line between Harrow and Rickmansworth used to have a limit of 75 mph for Turbo trains until the early 2000s but this has dropped since the London Underground A Stock was limited from 70 mph to 50 mph to improve reliability. The limit stays at 60 mph until Moor Park, where the speed drops to 50 mph. Just south of Rickmansworth, the line speed drops dramatically to 25 mph caused by the very harsh curve and numerous points. After Rickmansworth, the speed increases back up to 60 mph until Amersham, where the speed increases to 70 mph. All speed limits between Harrow and Amersham are for passenger trains only. Freight trains are not permitted to run on LU track except when the line is closed.

Amersham to Calvert
As the line passes back into Network Rail control the speed increase to 30/75 mph until south of Aylesbury where the speed reduces to 35 mph (due to Moorgate Control). Speed limits have risen by 25 mph in some places due to major track improvement work in the early 2000s. After Aylesbury the line is singled and speeds are 30/60 mph until the station at Aylesbury Vale Parkway. North of this station, the route continues to be single track, and the line speed is 30 mph until the end of the line at Calvert.

Services
Off peak services consist of:


 * 2tph (trains per hour) Marylebone — Aylesbury (operated by Chiltern Railways), with 1tph continuing to Aylesbury Vale Parkway (more at peak times).
 * 4tph Baker Street — Amersham (operated by London Underground)

Future

 * Following completion of a major track work project in December 2006, journey times on the line were cut by about 10 minutes. Currently major track replacement work is under way on the London Underground parts of the line, to increase maximum speeds.
 * The line north of Aylesbury was reopened to regular passenger traffic in 2008 as far as the new Aylesbury Vale Parkway station. In the long term, it is hoped to reopen the line beyond Aylesbury Vale Parkway to allow passenger services to reach Milton Keynes, Bedford and even Cambridge via a potentially reopened Varsity Line and East West Rail Link. This is under consideration as a result of expected heavy growth of the Aylesbury Vale area.
 * A proposal announced in March 2010 would route the future high speed line, High Speed 2, parallel with a section of the Chiltern Main Line. If this is undertaken, it will be a non-stop service, with no interconnects with the Chiltern Line.