What is "h-series"

The H-series rapid transit cars (the "H" standing for Hawker, the original manufacturer) was a subway car model built from 1965 to 1990 for the Toronto Transit Commission (TTC) in Toronto, Ontario, Canada. From 1965 to 1979, the cars were built by Hawker Siddeley Canada, and later by its new owner the Urban Transportation Development Corporation. The cars were built at the Thunder Bay plant. These cars used to be the standard cars for the TTC.