Chiocago Transit Authority 1983 Canadian Flyer work bus WB-2 at a job site. Chicago Illinois USA. July 2006.

I took this photo in Chicago's Wrigleyville neighborhood just east of North Clark Street one hot summer afternoon in July of 2006.

No longer carrying transit passengers, this 1983 CTA transit bus built by Flyer Industries of Canada is viewed at a work site location underneath the CTA red line elevated structure east of North Clark Street.

The maintenance crew members from this bus, are more than likely performing electrical repairs and inspections on the elevated rapid transit structure.

Many times over in most any city, when a bus is either at or past their normal service lives...they sometimes are demoted in to maintenance work services buses.
This practice hails back to the electric streetcar era.