Rail emissions can be a concern because railway switching yards and rail lines are often located near populated areas. Trains are powered by very large diesel engines. The pollutants emitted by trains are similar to those emitted by large trucks.
Railway locomotives produce a relatively higher proportion of sulphur dioxide (SO2) emissions than on-road diesel engines since the diesel fuel used by locomotives has a higher sulphur content.
In British Columbia, rail transportation is about 1.6% of total emissions of fine particulate matter, 1.2% of SO2 emissions, and 9.5% of NOx emissions.
On-road diesel engines are required to use ultra-low-sulphur diesel fuel with less than 15 mg/kg sulphur content.
Rail emissions in Canada are regulated by Transport Canada and Environment and Climate Change Canada. These agencies are working to align Canadian locomotive standards with those in the United States.