[jyl]

I see it as a noise pollution thing.

The diesel p/u pulls to the curb and idles while the driver does whatever, and as long as he is there, everyone in the immediate area is unable to hear or talk normally.

Kind of like if someone sets down an old-style boom box on the sidewalk and blasts loud rap so that you can't hear or talk normally. Or if someone pulls up on a Harley and sits there, revving through straight pipes. Or throws a big party at their house so that you hear the thudding through your bedroom walls.

How much inconvenience is it reasonable to impose on the people around you?

Depends on the cost and trade offs, of course. I don't know how feasible it is to quiet down your typical 3/4 ton diesel pickup that is idling at the curb while its single occupant talks on his cellphone or whatever he is doing?

I'm not talking about actual commercial work trucks, naturally if you stroll onto a construction site or truck stop, you shouldn't expect anything but noise. I'm talking about diesel p/us when being used as around-town putt putts. They can be tolerably quiet inside the cabin, due to all the soundproofing, but there seems to be little effort to make them quieter to the outside world.