"Key trains have one or more loaded tank cars of dangerous goods that are toxic by inhalation; or contain 20 ... (Inside Logistics Online Staff, 2020)
References:
Inside Logistics Online Staff. (2020, November 9). Ottawa orders trains to slow down in the cold. Retrieved from Inside Logistics: https://www.insidelogistics.ca/regulatory-legislative/ottawa-orders-trains-to-slow-down-in-the-cold-173448/