This bus would get along much better and use less fuel with a modern tier 2 or better repower. The GM 2 stroke diesel is a hugely polluting engine, glad to see it go.

Add on emissions devices might come around but the problem is making sure they actually do something on a wide range of vehicles / engines.

Those that think no emission controls should be used need to look at pictures of LA in the late 50's or talk to someone that lived there then. ( Or even go to major cities in China. )