ExpressTram

The ExpressTram is an automated people mover system operating at Detroit Metropolitan Wayne County Airport, in Romulus, Michigan, USA. The driverless system transports passengers along Concourse A of the airport's Edward H. McNamara Terminal, which is the world's second-longest airport concourse. Detroit Metro Airport serves as the second largest hub for Delta Air Lines, after Atlanta. The ExpressTram entered service when the McNamara Terminal opened on February 24, 2002.
Technology.
The system was custom designed by Poma-Otis Transportation Systems, a joint venture between Otis Elevator Company and Poma that has since been dissolved. Installation was performed by Otis, who currently operates and maintains the system.
The system operates above the main floor, and it consists of two cable-driven trams that ride upon an air-cushion, similar to a hovercraft. 3-PSI of air pressure is enough to lift the tram vehicles approximately 1/2" above the guideway surface. (The same "Hovair" technology is used in the Hub Tram and the Cincinnati Airport People Mover) Each tram is made up of two cars and can carry up to 208 passengers at a time. The track, referred to as a guideway in the APM industry, is over long.
LED displays in the stations, and in the trams, provide information, such as the upcoming stops, supplemented with a pre-recorded male voice which delivers audio information and warnings.
Route.
The ExpressTram services three stations along Concourse A. The stations at the ends of the concourse are appropriately named the North Station (which serves gates A56-A78) and the South Station (which serves gates A1-A28). The center station serves gates A29-A55, Luggage Claim, Ground Transportation, and Concourses B and C. The center station is officially known as the Terminal Station, based upon its close proximity to the main terminal building, which houses baggage claim, airline check-in counters, and ground transportation facilities. A maintenance garage lies beyond the North Station.
The system's primary infrastructure consists of a single guide-way with a bypass. When approaching the Center station, one tram veers off from the main guideway into the bypass, allowing the two trams to pass each other. The bypass reconnects to the main portion of the guideway beyond the center station. Operating software attempts to keep the trams synchronized, so that the trams arrive at the Center Station simultaneously, but this is not essential. In the event that trams lose synchronization, as is frequently the case with passenger induced delays, the first tram to arrive at the Center station will be held until the opposite tram enters the bypass area, providing a clear path for the waiting tram.