The system was approved for construction in 1969, to be built alongside the new satellite terminals as the first inter-terminal train system in the United States. It was completed in 1972 at a cost of $5 million and opened to the public in July 1973. The opening was delayed due to a dispute between the Port of Seattle and Westinghouse, the manufacturer of the system, over contracted costs. The system opened in 1973 at a total cost of $14 million. The original system consisted of nine vehicles; an additional three were added in the mid-1970s. The system was designed to have a capacity of 14,400 passengers per hour and travel at a maximum speed of. The original STS vehicles were built by Westinghouse and had a maximum capacity of 102 passengers. The average travel time for the two loops was 3.3 minutes, and 1.8 minutes on the shuttle, and each vehicle was estimated to amass annually. In 1999, the Port of Seattle authorized $142 million to completely overhaul the entire STS system. The overhaul included all aspects of the system including trains, controls, power supplies, stations, emergency ventilation systems and maintenance shops. The upgrade and modernization was completed in 2003. The 21 Bombardier Innovia APM 100 vehicles use CITYFLO 650 signaling technology and a radio Communication Based Train Control system for its automated operation.
Layout and operation
The STS is located within secure areas of the airport. The system consists of six stations serving each of the four gate concourses extending from the main terminal, and the North and South Satellite terminals. Each station is equipped with platform edge doors. The system consists of two loops serving the satellite terminals and a third line connecting the two loops in the main terminal.
The North Terminal Transit Loop is in length and has stations in the north end of the Main Terminal, Concourse C and the North Satellite.
The South Terminal Transit Loop is in length and has stations in the south end of the Main Terminal, Concourse B and the South Satellite. This loop is unique in that the first car of each train is outside of the "sterile area" of the airport. Passengers on most international flights arrive at the South Satellite, where they are processed by U.S. Customs and Border Protection officials. After inspection, passengers are taken to the STS station where they have the option of waiting in line to be inspected by the Transportation Security Administration so that they may access the rear two cars and secure area of the airport or directly boarding the first train car which transports them to the airport exit and the baggage claim area of the Main Terminal. The platform screen doors for this car do not open at the Concourse B station to prevent unscreened passengers from accessing that terminal.
The North/South Terminal Transit Connection is in length and has stations at both the north end of the Main Terminal and the south end of the Main Terminal, and serves as a connection between the North and South Terminal Transit Loops.
Public art
As part of its 2003 renovation, public art projects were included in the scope of the project. The main terminal's south station features a series of 56-plus flowers cast of aluminum and aluminum/resin mix created by Nancy Blum. In the main terminal's north station is a series of nine paintings created by Karen Ganz representing various travelers.
