Real-world driving emissions for private sector

Real-world driving emissions for private sector

An essential resource for manufacturers and private firms with a need to accurately benchmark emissions performance and tracking, and better understand emissions apportionment in their fleets.

Ricardo has an ongoing programme of measuring real-world driving emissions in England, Scotland and Wales. This has enabled us to build a unique database containing over 250,000 individual vehicle emission measurements – the largest database of real-world emissions information in the UK.

These measurements have been taken in a variety of conditions and have been carefully matched to comprehensive vehicle information databases. The measurements provide an unprecedented level of information on the real-world driving emissions from a very wide range of vehicle types on UK roads. The database provides comprehensive insight into the nature of real-world driving emissions, taking account of many of the important differences between fuels, technologies, driving conditions and environmental factors such as ambient temperature and road gradient.

There is growing evidence that emission factors used widely across Europe underestimate real-world driving emissions leading to uncertainties in the emission estimates. Of particular concern are those used for oxides of nitrogen (NOx). These uncertainties are not only manifest in the absolute rate of emissions from vehicles, but also in the relative differences between vehicles. Air quality modelling, which relies on accurate emissions factors, propagate inaccuracies and uncertainties into predicted ambient concentrations, potentially resulting in air quality assessments and policy decisions that are not representative of the real-world today, or when considering future year predictions.

Ricardo’s database minimises uncertainty, helping to focus attention on parts of the vehicle fleet that offer the major opportunities to reduce emissions and improve air quality.
For vehicle manufacturers and private firms, Ricardo’s database of real-world driving emissions offers:

  • A consistent basis upon which to compare own models with those of anonymised competitors, through the different Euro emissions standards.
  • A unique data set that supports the tracking of progress in reducing real-world emissions over time and the estimation of future impacts based on projected fleet mixes.
  • Insight into the performance of the most recent vehicle models and the differences between emission abatement technologies such as lean NOx traps (LNT) and selective catalytic reduction (SCR).
  • Information to support scenarios testing of emissions, through to dispersion modelling to quantify the impact on concentrations of pollutants such as nitrogen dioxide (NO2).
  • Detailed source apportionment information to quantify the contributions made by different vehicle types and technologies. Source apportionment information provides the data necessary to quantify the contributions to total emissions by different fuels, vehicle types, manufacturer models etc.
  • Insights into the effects of emissions deterioration based on actual measurements. For passenger cars, the Ricardo database provides a record of the mileage of a vehicle based on its last MOT test. This enables mileage and age-based deterioration effects to be quantified.

The Sankey diagram below shows emissions of NOx from petrol and diesel passenger cars, weighted by the contributions to total emissions from individual vehicle manufacturers. On the far left of the diagram, diesel cars account for the bulk of the emission of NOx. Moving to the right, the contributions are then split by Euro classification, which shows Euro 5 cars make the largest contribution. Then the contributions are disaggregated by the top 10 manufacturers in terms of vehicle numbers (anonymised). Finally, the far right of the diagram shows the overall contribution from all manufacturers. Such information can be used to quantify and visualise the contributions made to overall emissions under real-world driving conditions.


The data can also be used to consider how a particular vehicle model’s performance compares with that of similar vehicles when averaged over real-world driving conditions. The figure below highlights a particular manufacturer model Euro 5 diesel car and how its performance compares with that of other models. The error bars show the 95% confidence interval in the mean NOx emission under real-world driving conditions.

A further example of the insights that the Ricardo database offers is shown below. This highlights the change in emissions of NOx when going from Euro emissions standard 5 to 6 for different manufacturers of diesel cars. The data reveal that many manufacturers show impressive reductions in the emissions of NOx – but, equally, there are several where the reduction is less impressive. These data can be split further by different models of vehicle and by LNT/SCR.

To find out how Ricardo’s database of real-world driving emissions data could help your business efficiently benchmark performance, improve emissions tracking and better understand apportionment, please contact david.carslaw@ricardo.com