Airports of London / Hertfordshire border, Luton Airport is London's fourth-largest airport, the fifth-busiest in the United Kingdom and the third-closest to the capital, after Heathrow and City airports. The two airlines supplying most passenger capacity are the low-cost carriers easyJet and Wizz Air. Luton Airport Parkway railway station can be reached from London St Pancras in as little as 22 minutes via East Midlands Trains, while Thameslink is the primary operator, with slower but more frequent services. A shuttle bus service connects Luton Airport Parkway to the airport, a distance of just over a mile. Located in Essex, Stansted is London's third-busiest
Train protection system driver. This goes as far as some systems being nearly able to drive the train automatically. Indonesia, Ireland, Dominican Republic, Denmark) Train protection system A train protection system is a railway technical installation to ensure safe operation in the event of human failure. The earliest systems were train stops, as still used by the New York City Subway, the Toronto subway, the London Underground, the Moscow Subway (only on the older lines) and the Berlin S-Bahn. Beside every signal is a moveable arm. If the signal is red, levers connected to valves on any passing train hit the arm, opening