The rise and fall of Diesel


The rise and fall of Diesel

By Scott Leitham, Director of Transport Planning

The use of diesel vehicles in cities is increasingly being recognised as a major factor behind poor urban air quality, and this in turn is linked to a range of negative health impacts and indeed premature deaths. In many European cities, air quality limits are regularly being breached. To counter this, some city authorities are considering bans on some or all diesel vehicles, and there have been calls for scrappage schemes and other tax measures to counter the use of diesel. In Central London, a new £10 surcharge on older diesel cars will be introduced in October 2017.

How did we get here?

Diesel engines are typically characterised by lower fuel consumption than a petrol equivalent, therefore they produce lower emissions of CO2, the main greenhouse gas. In the early 2000s, a range of government policies were introduced aimed at reducing CO2 emissions. These included a company car tax regime based in large part on CO2 emissions (2002) and also an emissions-based system for Vehicle Excise Duty (2001). Both measures were aimed at encouraging drivers to use more fuel efficient vehicles, and by implication in many cases diesels. These measures have led to the percentage of diesel cars on the road increasing from 13% in 2000 to 38% today (it was only 7.5% in 1994). In 2016 sales of petrol and diesel cars were similar and this has been the case over recent years.

However, although diesel offers improvement in terms of global emissions, it is worse in terms of the amount of local air quality pollutants such as Nitrogen Oxides (NOX) and Particulate Matter (PM), both of which are linked to respiratory problems and a range of other health impacts.

What about engine regulations?

European Regulations set limits on the level of a range of emissions by vehicle type. There have been six sets of regulations from Euro 1 (1992) to the current Euro 6 (2014) as shown below.

From the first limit which was set to the present day, emissions of NOX and PM from diesels have in theory dropped by 84% and 96% respectively. On the face of it, this level of reduction in emissions could be expected to be reflected in urban air quality, effectively dealing with this issue.

Why hasn’t this worked?

The ‘Euro’ tests are undertaken in controlled laboratory conditions. It emerged in 2015 that VW had been fitting ‘defeat devices’ to their vehicles, where these devices detected ‘test’ conditions and modified the vehicle’s behaviour to comply with the tests. In the wake of this the DfT undertook research to investigate ‘real world’ emissions of NOX compared to the Euro test figure for Euro 5 and Euro 6 compliant cars.

Across a range of vehicles tested from all the main manufacturers, both the Euro 5 and Euro 6 vehicles were emitting more than 6 times the amount of NOX recorded in the Euro lab tests. The technical measures to reduce PMs have been effective, principally through the use of filters. although some car owners do have these filters removed to improve fuel consumption.

In summary…

Government policy set out to tackle one problem (CO2 emissions) and then created/exacerbated another one (local NOX and PM and the resulting air quality issues). The European regulatory regime designed to control vehicle emissions has failed, as manufacturers widely ‘gamed’ the testing, and the testing regime was not reflective of real world driving – a decision on new European testing regime is expected soon. Air quality in major cities has not improved and continues to fail to meet standards in many cases

Globally, VW sales increased in 2016! More widely car manufacturers do not appear to have incurred significant lasting reputational damage. There is, however, increasing negative media publicity surrounding all diesel – there is some evidence of a decline in diesel sales, even though manufacturers continue to invest heavily in diesel technology.

The public is left very confused, those with existing diesel vehicles (bought in good faith) risk financial losses through further tax measures/impacts on residual value, and manufacturers face uncertainty over the regulatory regime. However, diesel cars are not the only problem – in London, diesel cars were responsible for only around 12% of NOX emissions (buses & HGVs contributing a further 21%).

Overall, these developments need to be seen in the context of the potentially major technological changes affecting the vehicle fleet in the medium term. PBA is fully abreast of this evolving technological and policy area, and builds this thinking into the advice provided to clients on the implications of these changes across all areas of the Practice.