A few days ago the government introduced the Green Vehicle Guide, that purports to inform consumers of the most environmentally friendly vehicles in the Australian market. I was interested to see that the Toyota Prius, lauded worldwide for its clean nature, was nowhere near the top of the list. In fact, if you search all vehicle types, and sort them by their air pollution rating, you'll find the Jeep KJ Cherokee Sport on top, closely followed by the Mercedes-Benz CL55K, a 5.5 litre V8.
I find these results slightly alarming, and not quite in tune with what the average person would consider as pollution. The guide gives a pollution rating based on the most stringent emission standard that the manufacturer claims. Cars that conform to the Australian standard, such as the Toyota Prius, receive a 5 out of 10. The Jeep mentioned above claims to conform to a stricter standard.
The unfortunate thing is that the cars are not actually tested to see what emissions they actually produce. As a result, we have weird situations such as this, where manufacturers' claims take precedence over physics.