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 The London Underground is frequently studied by academics because it is one of the largest, oldest, and most widely used systems of public transit in the world. Therefore, the transportation and complex network literatures include extensive information about the Tube system. For London Underground passengers, research suggests that transfers are highly costly in terms of walk and wait times. Because these costs are unevenly distributed across stations and platforms, path choice analyses may be helpful in guiding upgrades and choice of new stations. Routes on the Underground can also be optimized using a global network optimization approach, akin to routing