As per the the Interweb;

Here is a list of all states currently conducting diesel emissions testing.
Connecticut. Counties: All. ...
Colorado. Counties: Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and Jefferson. ...
Arizona. County: Maricopa. ...
California. Counties: 40 of 58 (high population areas) ...
New York. ...
Nevada. ...
Utah. ...
Wisconsin.

And directly from Washington State web site (where I live);

These diesel vehicles no longer require an emission test:
All diesel powered passenger vehicles weighing less than 6,001 pounds.

All diesel vehicles model year 2007 and newer, regardless of weight.

VW diesel vehicles
These vehicles are not required to be emission tested in Washington.


It's going to turn into the same situation as it has in the Power and Oil Refinery industry. They already require permitting to install and continuous monitor with selective catalyst reduction, which we have on newer trucks. .

 

No reason to test VW vehicles, They have a defeat device from the factory...

And all of the other vehicles you can program you way past the SCR - which is why some want to test. It's a waste of time on a newer vehicle. Plus, there is a lot of push back from manufacturers and dealers to test. One reason is that occasionally you do get that 1% of the new vehicles that no matter what you do they don't pass and they end up having to get bought back...

They used to test all vehicles in Florida and then just in some of the more populated areas and it was a waste of resources. It created more pollution because you had to wait forever to get the vehicle tested. It really sucked.

According to my neighbors they used to test in Anchorage and Fairbanks and then realized the same thing, 99% of the vehicles would pass or where so old that they were exempt. So they stopped it. It can also get difficult to get a vehicle out of open loop when it's -40 out.