The Expo Line is SkyTrains oldest Line, opened in time for the 1986 Expo, and was called just SkyTrain (as the only line) until 2002 when the Millennium Line opened which is through routed over most of the Expo Line except for the four southernmost stations in Surrey. Most of the Expo Line is elevated (with a few stations on a grade or in open-cuts) except for the tunnel through downtown, which is a retrofitted former railroad tunnel. The stations are all fairly modular in appearance with no glass present just white mesh windscreens and simple canopies generally held up by beams painted green.

The line uses linear induction technology, trains are automated and driverless, and Mark-I cars (although Mark-II Millennium Line Cars are used interchangeably) identical to those on the Detroit People Mover (and similar to Toronto's Scarborough RT). Newer cars have also been introducted including Mark III cars and Mark I trains being lengthened from four to five cars.