><quote>
>Volkswagen is being rightly condemned from all directions, as its
>methods were particularly cynical: its engine software would sense when
>the car was in a test environment and cut back NO_x output temporarily.

>As soon as the car was no longer under test, the car would change mode
>and emit huge amounts of NO_x. This wasn't done for no reason – if a
>machine is allowed to generate NO_x freely, it can be very
>fuel-efficient – and thus, of course, its carbon emissions can be very
>low too.

I noticed that (at least!) one media report portrayed this as making VW's less "green".  But from another report, I saw that they had 10% greater gas mileage if they were allowed to cheat.  (In other words, less CO2 emissions per mile.)  Now, the above quote refers to "huge amounts" of NOx.  (nitrogen oxides, probably NO and NO2).  The question is, for those people who complain about CO2 being a greenhouse gas, what is the relative undesireability of extra CO2 versus extra NOx.  Relative harm, and all that.  Which is a concept that people who call themselves "environmentalists" seem to have a great deal of difficulty with.

This also raises an idea:  I've never heard of this, but what would be wrong with allowing differences in emissions based on location?  Putting a GPS in a car is trivial today.  Producing less NOx inside a city would make sense; producing less NOx while on a cross-country road-trip less so.

                    Jim Bell