Airports of London runways. Due to the location in London's western suburbs, Heathrow has had trouble trying to expand, with various expansion projects being cancelled.) As a result, the airport consistently runs at over 99% capacity and is often included on lists of the worst-rated airports in the world. However, on 1 July 2015 Heathrow's expansion plan was suggested as the best option by the Airport Commission and on 25 October 2016 a new northwest runway and terminal was approved by the Government. The airport is connected to Great Britain's motorway network via the M4 and M25 motorways, to London Paddington station by
London Underground infrastructure lines share all their stations and most of the track with other lines. The Bakerloo, Central, Jubilee, Northern, Piccadilly, Victoria and Waterloo & City lines are deep-level tubes, with smaller trains that run in two circular tunnels with a diameter of about , lined with cast-iron or precast concrete rings, which were bored using a tunnelling shield. It is these that were the "tube" lines, although since the 1950s the term "tube" has come to be used to refer to the whole London Underground system. Many of the central London deep-tube line stations, such as those on the Central and