The Four Lines Modernisation (4LM) is a series of projects by Transport for London to modernise and upgrade the sub-surface lines of the

London Underground The London Underground (also known simply as the Underground or by its nickname the Tube) is a rapid transit system serving Greater London and some parts of the adjacent ceremonial counties of England, counties of Buckinghamshire, Essex and He ...

: the

Circle A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the centre. Equivalently, it is the curve traced out by a point that moves in a plane so that its distance from a given point is const ...

District A district is a type of administrative division that, in some countries, is managed by the local government. Across the world, areas known as "districts" vary greatly in size, spanning regions or counties, several municipalities, subdivisions o ...

, Hammersmith & City and Metropolitan lines. The upgrades entail new rolling stock, new signalling and new track and drainage

Rolling stock

S7 Stock 21347+48 and D78 Stock 7007+7032

As part of the upgrade, the entire sub-surface fleet was to be replaced. S7 and S8 Stock manufactured by

Bombardier Transportation Bombardier Transportation was a Canadian-German rolling stock and rail transport manufacturer, headquartered in Berlin, Germany. It was one of the world's largest companies in the rail vehicle and equipment manufacturing and servicing industry ...

Derby Litchurch Lane Works Derby Litchurch Lane Works (formerly Derby Carriage and Wagon Works) is a railway rolling stock factory in Derby, England. It was opened in the 19th century by the Midland Railway. The plant has produced rolling stock under the ownership of the ...

were ordered to replace a variety of rolling stock, these being the A60/62 Stock on the

Metropolitan line The Metropolitan line, colloquially known as the Met, is a London Underground line between in the City of London and and in Buckinghamshire, with branches to in Hertfordshire and in Hillingdon. Printed in magenta on the tube map, the line i ...

, the C69/77 Stock on the

(Edgware Road to Wimbledon section) and Hammersmith & City lines, and the D78 Stock on the

District line The District line is a London Underground line running from in the east and Edgware Road in the west to in west London, where it splits into multiple branches. One branch runs to in south-west London and a short branch, with a limited servic ...

, which all dated from the 1960s and 1970s. The order was for a total of 192 trains (1,403 cars), and formed of two types, S7 Stock for the Circle, District and Hammersmith & City lines and S8 Stock for the Metropolitan line. The main differences, aside from the number of cars (S7 having seven cars and the S8 having eight cars), were in the seating arrangements, in which the S7 Stock consisted of a longitudinal-only layout, whereas the S8 Stock had a mixture of longitudinal and transverse seating. New features that were not used on the previous rolling stocks included air-conditioning, low floors to ease accessibility, and open gangways between carriages. The entire fleet was introduced by April 2017.

Signalling

Part of the modernisation includes the introduction of

Communications-Based Train Control Communications-based train control (CBTC) is a railway signaling system that uses telecommunications between the train and track equipment for traffic management and infrastructure control. CBTC allows a train's position to be known more accurat ...

(CBTC) to allow for Automatic Train Operation (ATO). In order to upgrade the signalling, Signal Migration Areas have been created to allow for the gradual installation. Below is a list of the SMAs and their progress: As a result of the first 6 SMAs being installed, the

and Hammersmith & City lines now runs entirely under ATO. Originally the SMAs were planned as follows: For various reasons including funding and the technical difficulties with sharing tracks with

National Rail National Rail (NR) is the trading name licensed for use by the Rail Delivery Group, an unincorporated association whose membership consists of the passenger train operating companies (TOCs) of England, Scotland, and Wales. The TOCs run the p ...

& the

Piccadilly line The Piccadilly line is a deep-level London Underground line running from the north to the west of London. It has two branches, which split at Acton Town, and serves 53 stations. The line serves Heathrow Airport, and some of its stations are n ...

, SMAs 10-12 were scaled back until further notice.

References

External links

* {{Official website London Underground