rest of the United Kingdom and with other cities across the European mainland. Many domestic services are run by National Express, with international services mainly provided by Flixbus and Eurolines. National Express' predominantly white vehicles are common on the roads of central London, on their way to and from their terminus at Victoria Coach Station. In 2006, competition for long-distance traffic was introduced by Megabus, a subsidiary of the large UK bus operating company Stagecoach. This company operates cheap services aimed at students and the like, which must be booked in advance on the internet. Other coach services link London to medium-distance destinations, and unlike National Express or Megabus provide walk-on fares. Good examples of this are the Green Line services to the Home Counties, mainly operated by Arriva, the service to the city of Oxford, where Stagecoach's frequent Oxford Tube service competes with Go-Ahead's similar Oxford Express service, and the many commuter services to medium-distance destinations operated by individual coach companies during peak times. Airport buses National Express is also the principal airport bus operator, serving Heathrow, Gatwick and Stansted with its National Express Airport brand. Unlike their longer distance cousins, these are walk-on services, which serve stops throughout central London rather than running to Victoria Coach Station. Bus and coach stations There are around 50 bus and coach stations across London, located at transport interchanges, town centres and other major destinations such as shopping centres and hospitals. The busiest coach station in London is Victoria Coach Station, which serves around 14 million passengers a year. Cromwell Road bus station in Kingston upon Thames is the largest London Buses bus station, with 17 bus stands. Major accidents and incidents October 1940: LT 669, operating on route 88, was abandoned by its passengers and crew on Balham High Road seconds before a bomb fell, creating a huge crater into which the bus rolled. It was hauled out of the crater two weeks later. 13 June 1957: RTL 780, operating on route 7 collided with a queue of people at a bus stop in Oxford Street, resulting in eight deaths. The driver had collapsed with heat exhaustion. 18 February 1996: An explosive device detonated prematurely on a route 171 Catford to Holborn double-decker bus, operated by London Central, in Aldwych. The bomb killed Edward O'Brien, the IRA terrorist transporting the device, and injuring eight others including the driver. The force ripped