Whoa there, hold your horses. There are many things that affect people in many different ways. There were a couple of whistleblowers about their findings of the air quality on the London Underground, with readings many times worse than were found standing in the middle of the most congested roads in London. This was also backed up by scientific studies and reports carried by hospitals and doctors, which proved the air there was directly responsible for the men's chronic breathing and general health problems. You say that this one man's tests are conclusive when it was possibly a means to an end? I suggest that more people are exposed to poor air on the tubes then there are being exposed to the road traffic fumes on a daily basis, and those on the underground are alo more likely to be exposed for longer periods to those using the roads in the fashion that James Gallagher did for his "experiment" The SMMT figures do not show actual true sales, i.e., cars that have been sold and are being used on the roads, they only show cars that have theoretically been sold, when in reality many of these have been registered and then within days or weeks, declared as SORN and placed into storage. These cars are NOT contributing to the clean air that I keep hearing so much about are they? In fact there is an argument to be made that they are adding to overall pollution levels as they have had to be made and shipped all around the world and then become stored and later sold as used cars with delivery miles on them. The DVLA are aware of the number of new car registrations, they are also know what their drivetrains are, ie, petrol, diesel, HEV (predominantly petrol), PHEV, again petrol) and BEV. They will also be aware of how many of each type are also subsequently declared as SORN and their drivetrain types, as well as dates that they were first registered and when they were SORN and therefore can also tell how long that period was, how long the car has been with each new registered owner and also tell you who these keepers are, traders or private people. But they are not willing to provide such information, why do you think that might be??