The lack of recent progress in cleaning urban air can be blamed on the steady increase in diesel vehicles; over half of new cars are now diesel, compared to just 14% in 2000.

 

It is harder to control pollution from diesels than from petrol, and for this reason, European standards for diesel exhaust have not been as strict as those from petrol cars. Access to low emission zones in Germany reflect the difference in pollution emissions with open access being permitted for petrol cars made after 1993 but only for the most modern diesels. It is also becoming clear that the technologies to control some types of pollution from diesels are not effective during real-world driving.

 

The air pollution penalty from diesel cars is often justified in terms of the saving in CO2 emissions compared with petrol. However, new analysis is calling this orthodox view into question. If climate warming emissions of black soot are considered along with the difficulties of producing sufficient diesel to meet demand, then the climate change benefits from diesel largely disappear.

 

Japan has taken a different course. Through innovation in petrol engine technologies it has been able to reduce average car CO2 emissions faster and more effectively than Europe without the urban air pollution problems from diesel cars. Additionally, with the recent classification of diesel exhaust as carcinogenic, it might be time to reconsider the recent boom in diesel fuel use across the UK and Europe.