A couple notes:
* The 870 was the first transit bus to use the front turn signals as "parking lights" like a car. The reason was, the original 870 was designed without eoofline corner marker lights (they only had the three-light sets on the front and rear roof which are federal requirements), and the wraparound turn signals were to serve as the front side marker light; the wraparound taillight was to be the rear side marker light. Most operators asked for the top-side marker lights, and many states required them anywat, so in 1979, they were made standard.
* Unlike the RTS, the upper fixed portion of the 870-Metro-A driver window was hinged at the top as an emergency exit.
* The original Metro A was introduced with RTS-shape wheel arches instead of the round shape used on the 870 (which Flxible then returned to)
* The Metro C introduced the smaller "teardrop" marker lights (similar to the ICC roof lights of the last GMC New Looks). 870s and Metro As and Bs used the larger rectangular marker lights.