Marty:
When we were looking around before we bought our Georgetown, we looked at a number of Chevy and Workhorse rigs. They all had the dreaded "Autopark" system. This is a hydraulically operated parking/emergency brake that is mocked up to look like the rig has air brakes.
It has one major disadvantage that made us decide no way we'd buy one. The primary failure mode of the system is to apply the parking brake, even if you're on the freeway at 60 mph.
You might want to do a search on "Autobrake". It made me a firm believer in the F53 Ford.
