A new train system, dubbed AeroTrain and developed by Mitsubishi, began in 2010 to transport passengers between the concourses and the main terminal. The system, which uses rubber tires and travels along a fixed underground guideway, is similar to the people mover systems at Singapore Changi Airport, Hartsfield–Jackson Atlanta International Airport, and Denver International Airport. The train is intended to replace the mobile lounges, which many passengers found crowded and inconvenient. The initial phase includes the main terminal station, a permanent Concourse A station, a permanent Concourse B station, a permanent midfield concourse station (with access to the current temporary C concourse via a tunnel with moving walkways), and a maintenance facility. Mobile lounges continue to service the D Concourse from both the main terminal and Concourse A. Even after AeroTrain is built out and the replacement Concourses C and D are built, the mobile lounges and plane mates will still continue to be used, to transport international arriving passengers to the International Arrivals Building, as well as transport passengers to aircraft parked on hardstands without direct access to jet bridges. Dulles has stated that the wait time for a train does not exceed four minutes, compared to the average 15-minute wait and travel time for mobile lounges.