While it makes good headlines, I think most of this could be summed up as &quot;vehicle emissions are more complex than the simple model you might expect&quot;.<p>Go and read the Wikipedia page on the New European Driving Cycle - <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;New_European_Driving_Cycle" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;New_European_Driving_Cycle</a>. Notice that in the test procedure every instance of acceleration is described as &quot;the car slowly accelerates&quot;. Now think about the range of driving styles that are found in the real world. Some people might be quite laid back about accelerating, but I think there&#x27;s an awful lot of &quot;floor the accelerator to get back up to the speed limit&quot; as well. It&#x27;s hardly surprising that in those periods the emissions from the engine will be higher than they were under the test cycle.<p>So who do we blame? The vehicle manufacturers? Well, given current popular sentiment, down that path may lie vehicles which are designed to never exceed the emission limit. At the extreme end we might finish up with cars that automatically throttle back when they hit an emission limit, similar to processors throttling back when they hit thermal emission limits. But what do we do when we start having fatal accidents when people tried to overtake and the engine suddenly reduced power in an unpredictable way because it had gone over the emission limit?<p>So, blame the emissions tests? Well, what should the emissions test be targeting? Never going over a particular threshold, say? In which case, how do you define a standard protocol (to ensure fairness across vehicles) that all vehicles will be able to follow? At one end you&#x27;ve got cars like the Peugeot Bipper Tepee with a 0-60 time north of 16 seconds (with both petrol and diesel engines - <a href="http:&#x2F;&#x2F;www.honestjohn.co.uk&#x2F;carbycar&#x2F;peugeot&#x2F;bipper-tepee-2009&#x2F;?section=data" rel="nofollow">http:&#x2F;&#x2F;www.honestjohn.co.uk&#x2F;carbycar&#x2F;peugeot&#x2F;bipper-tepee-20...</a>). At the other you&#x27;ve got cars like the BMW X5 4.4 V8 which can accelerate roughly twice the mass in a quarter of the time (<a href="http:&#x2F;&#x2F;www.honestjohn.co.uk&#x2F;specs&#x2F;detail&#x2F;?v=MBMWI-X50311" rel="nofollow">http:&#x2F;&#x2F;www.honestjohn.co.uk&#x2F;specs&#x2F;detail&#x2F;?v=MBMWI-X50311</a> - the diesel engined version isn&#x27;t far behind either). I&#x27;d imagine that a protocol that produces the highest emissions from the BMW would not even be achievable by the Peugeot.<p>The only other party left to blame seems to be the drivers, and particularly their inability or unwillingness to drive in a style that minimises emissions (and at the same time most likely increases fuel economy). But the media seem reluctant to point the finger in that direction.<p>I think we need to blame all of the above, but we need to get past the simplistic model of emissions being a constant that you can set a limit on for all vehicles regardless of how they are driven.