What are the types of heavy rail transportation systems in Ontario?

In southern Ontario’s Golden Horseshoe region, GO Transit operates seven heavy rail commuter transit routes. The Union-Pearson (UP) Express is a 23-kilometre long airport rail link between Union Station and Toronto Pearson International Airport that is classified as a heavy rail system. Via Rail is a Crown corporation designed to facilitate inter-city travel across Canada, including routes along the Windsor-Ottawa corridor and some routes reaching the northwestern portions of the province. Two national railway companies, the Canadian National (CN) Railway and the Canadian Pacific (CP) Railway, and an additional 17 other rail companies operate routes either within Ontario or between provinces including Ontario. Passenger service on these systems is generally limited and most of these trains are used for freight service.