rapid transit 
noun [mass noun, usually as modifier]
A form of high-speed urban passenger transport such as an elevated railway system: a rapid-transit light rail system...
- The mass rapid transit system and the public bus services, from my own attempts in getting around, are commendable for their convenience.
- The Taipei City mass rapid transit system was severely hit by yesterday's earthquake, with service suspended for several hours.
- I think you need an interconnected system of rapid transit.