[leegreen]

I'd intended my question as rhetorical, for light vehicles like our trucks 'parking' vs 'emergency' is just a word choice despite distinction made in the legislation.

Heavy vehicles with air brakes have true emergency braking as the brakes self apply if the system fails. Unlike our hydraulic brakes.

I regard the parking brake action of rear drums as superior to that you get with rear disk, regardless of the mechanical brake being part of the caliper or a miniature drum inside the hub. No personal experience with the sperate mechanical caliper some cars have / wilwood sells -but the pads look small

I'd never trust just having the rear wheels locked up for loading / unloading a car trailer or boat trailer. Service brakes applied, wheels chocked, locked up in 4wd - something to save you when the weight comes off the back wheels.