Neil Williams wrote:
On 2017-02-01 16:40:02 +0000, tim... said:

and how would you enforce "not using the engine" inside the zone?

I know it's a bit old fashioned and quaint, but how's about we have
some of those "police officers" walking and driving around the place?
You know, the kind that would see a crime being committed and
investigate, and if necessary issue a ticket or conduct an arrest?

I suspect that you could have automatic detectors that sniff out tailpipe
emissions from passing vehicles, and photograph them.