Yeah I’m not thinking so much stopping at lights and in traffic for this application, but something like if the parking brake is engaged and 15-30 seconds pass, then engine turns off. As the trucker in this thread noted, sometimes they’ll hop out expecting a quick stop and it balloons into 15 minutes of idle waiting on other people. Then there’s the drivers who will let the truck idle while getting loaded/unloaded just for climate controls… And thinking at scale saving even just a gallon, multiplied across a whole fleet, could be a big impact.
Of course there’s more thought to put in for secondary systems, but just strikes me as something that should be considered.
Cops will leave their engines running because they may have to go into service at a moment notice. Not sure if I entirely agree the half second to fire up is going to slow their response considerably, but I’d error on the side of an exception for emergency equipment.