The commuter rail system includes purpose-built double track for local services in two rail corridors along intercity railways, and the Ring Rail Line, an urban double-track railway with a station at the Helsinki Airport in Vantaa. Electric operation of commuter trains was first begun in 1969, and the system has been gradually expanded since. 15 different services are operated , some extending outside of the Helsinki region. The frequent services run at a 10-minute headway in peak traffic.