Many vehicles will still exceed official CO2 and NOx emissions figures even if drivers are trained to drive more efficiently, new research from Emissions Analytics has revealed.

The research underlines the benefits of driver training initiatives but finds that real-world emissions are still primarily determined by vehicle selection.

Working with Imperial College, the company had set out to find out how much driver behaviour affects fuel economy and emissions under real-world use, ahead of autonomous vehicles reaching UK roads.

Emissions Analytics fitted 21 vehicles with portable emissions measurement systems to analyse exhaust emissions, marrying that information with traffic simulation software to simulate the more responsible and consistent driving styles from autonomous vehicles.

The research was modelled to explore the effects of traffic flow and driving behaviour on nitrogen oxide (NOx) and carbon dioxide (CO2) emissions. This was used to assess the impact of different driving styles while incorporating varying degrees of automation.

With the results configured to emulate the greener driving styles that would be seen in autonomous vehicles, NOx and CO2 could be reduced by approximately 20% with full take-up of such vehicles on congested roads. This compares to general industry estimates that investing in eco driver training can improve MPG by up to 15%.

However, although the figures show optimised driving styles can deliver lower vehicle emissions, they also indicated that any reduction would still not bring emissions down sufficiently.

According to Emissions Analytics’ EQUA Index, on average diesel NOx emissions are approximately five times the regulated limit on average (399mg/km), and CO2 emissions are 40% above official values (based on the New European Driving Cycle).

This means that even if driven more responsibly the average vehicle will only reduce its NOx exceedances to about a factor of four thereby still exceeding legal limits, and the CO2 exceedances to 30%, still over official values.

The conclusion of the research is that even if the driver and all associated “bad” driving habits are eliminated, the current fleet of vehicles will still well exceed official CO2 values, and diesel vehicles will be over the NOX limits.

The findings also show that while driver training initiatives can bring about eco benefits, real-world emissions – as well as vehicle mpg – are still primarily determined by vehicle selection.

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