The Metropolitan Transit Commission (a division of the Metropolitan Council regional planning agency) took over the privately-owned Twin Cities Lines bus system on September 18, 1970. Most of the buses Metro Transit acquired were at least 15 years old and in lousy shape. The commission launched a five-year improvement plan to replace the old exhaust belchers with new, shiny red ones, but the process took time. Some of the old buses, like the one shown in this photo, continued to ply Twin Cities streets into the mid 1970s.
Photo via Old Minneapolis
I rode on one of these, the original 1953 streetcar-replacing buses, just the other day courtesy of the Minnesota Transit Museum. The best difference was having a back window, and being able to look out of it & see Lake Street vanishing off behind the bus.