NOx – The Curse of VRT

Mar 3, 2013 | Environment, News | 0 comments

A recent report in the Irish Times (27 February 2013) stated that whilst emissions of NOx fell 47% between 1990 and 2011 in Ireland, the levels of NOx in the air still exceeded the EU target of 65,000 tonnes by 4%. According to the article, the EPA stated that most of the reductions achieved by industry have been largely offset by increases in vehicle numbers.

However, this statement is misleading and is not the whole story as the EPA’s own data suggests that government policy has had the unintended consequence of increasing NOx emissions. In fact, contrary to the statement in the Irish Times report, it is not the increase in vehicle numbers that is responsible but the change from petrol to diesel vehicles prompted by the VRT system.

In a paper presented to the Irish Transport Research Network at University College Cork 2011, Leinert, Hyde and Cotter argue that the present VRT (Vehicle Road Tax) arrangements that link vehicle tax to CO2 emissions encourage drivers to purchase fuel efficient cars. They further argue that this policy has had the effect of changing car purchasing patterns so that now diesel engined cars make up a higher proportion of new car purchases that would otherwise be the case. This has reduced CO2 emissions per km which is good; however, as diesel engines emit far higher NOx levels than petrol engined cars per km, the effect has been for NOx levels to rise. The paper argues that this will cause NOx emissions to be 28% higher in 2020 than would otherwise be the case.

So now we have clear statement that a policy intended to moderate the long term menace of global warming (which is obviously a good thing) has the unintended consequence of increasing a very real health risk. The solution is then to re-design the VRT system to penalise both CO2 and NOx emissions. As well as reducing a health risk this will help Ireland achieve its NOx ceiling target. We know that VRT influences buyer behaviour so with a correctly designed policy we should be able to move purchasers away from diesel engines to smaller petrol engines. And there are other benefits as diesel engines are also responsible for high levels of particulates (PM10) which again is a serious health risk.

An overall for the VRT system is now required to ensure that a tax designed to influence buyer behaviour is based on a holistic approach to emissions rather than just a narrow target of CO2 reduction.