BART could be characterized as a "commuter subway," since it has many characteristics of a regional commuter rail service, somewhat similar to S-Bahn services in Germany, Denmark, Austria and Switzerland, such as lengthy lines that extend to the far reaches of suburbia, with significant distances between stations. BART also possesses some of the qualities of a metro system in the urban areas of San Francisco and Oakland; where multiple lines converge, it takes on the characteristics of an urban metro, including short headways and transfer opportunities to other lines. Urban stations are as close as apart, and have combined 2- to 5-minute service intervals at peak times.