In Toronto, every train has a driver, and the platform edge doors are only used for subway lines.
The doors on both the train and platform have to line up perfectly each time the train stops, and this can only be done with automatic train control, meaning driverless trains.
A few steps up a hill in a park in Toronto costs $10,000 and platform edge doors would cost much more.
The cost to complete the entire subway system in Toronto would be over a billion dollars according to an article on the website.
Since then there have been two big cost-of-living jumps in Toronto, so that adds up to more than a billion.