Our vehicle emissions research is focused on the use of remote sensing. Over the past few years a focus of this research has been the development of more robust information on the emissions of NO$_x$ and NO$_2$. Early work gave a strong indication that emissions of NO$_x$ from diesel light duty vehicles were not decreasing as expected, which later became a significant issue in the light of the ‘dieselgate’ issue Carslaw et al., (2011).
Main findings and interests
Below is a brief summary of our main findings and associated papers.
Carslaw et al., (2011) showed that based on extensive remote sensing measurements that NO$_x$ emissions were not decreasing as expected from light duty diesel vehicles and this lack of decrease could also be observed in the atmosphere. Coupled with increases in primary NO$_2$ emissions (Carslaw, 2005), these two effects combined to produce the European “NO$_2$ problem”.
Remote sensing in 2013 aimed to quantify the performance of urban bus retrofit technology using an SCRT technology. Results were encouraging but there were significant periods where the aftertreatment system was less than optimal, see Carslaw et al., (2015).
We showed that there was a strong ambient temperature dependence in light duty diesel NO$_x$ emissions following extensive measurement campaigns throughout 2017 and 2018 Grange et al., (2019).This finding may have important implications for emissions inventories of road vehicle NO$_x$ emissions and imply emissions may be overestimated in summer and underestimated in winter.
The first measurements of NO$_2$ in the UK were made in London Carslaw and Rhys-Tyler (2013). This work also showed the large differential performance of emissions control on vehicles and especially urban buses.
The focus during the latter half of 2019 will be the measurement of Heavy Duty Vehicles using the Denver FEAT.
Our research in the area of vehicle emissions benefits from several collaborations:
The University of Denver — where the vehicle emission remote sensing was developed by the late Professor Donald Stedman, and Dr Gary Bishop.
Ricardo, who make extensive measurements using the Opus RSD5000 instrument. We work closely with Ricardo — David Carslaw has a joint position, Ricardo supports two CASE studentships and we collaborate extensively.
OPUS RSE based in Madrid who develop the RSD5000 instrument. The University of York owns a RSD5000 instrument.
The CONOX partnership, which led to Europe’s first vehicle emission remote sensing database.
Most of our measurements have used the University of Denver FEAT instrument, which for a long time has had the capability of measuring NO$_2$ and NH$_3$, both of importance from a vehicle emission perspective. A specific interest in using the FEAT instrument was to robustly quantify direct emissions of NO$_2$.
Recent work has considered the potentially important effect of ambient temperature in affecting emissions of NO$_x$ from light duty diesel vehicles. This work for the first time measured at lower ambient temperatures than is typical for remote sensing campaigns.