1. Transport and air pollution
Air pollution: what is the scale of the problem and what can be done about it?
Dr Marc Stettler
Centre for Transport Studies | Department of Civil and Environmental Engineering Imperial College London
20th April 2017

2. London’s NOx emissions by sector
Katie King (Aether), APRIL meeting, 14th October 2016.

3. A transport impact identity…
Car sharing
Teleconferencing
Optimised logistics
Activity ↔ Economy
Cleaner engines (better emissions control)
Alternative powertrains (e.g. EV, hybrid)
AQ impact=Activity× Energy Activity × Emissions Energy × Impact Emissions
When I think about AQ impacts of transport and when I try to communicate the issues to my students for the first time, I like to start with a simple identity equation.
Some of you may have seen something similar before.
Essentially, the AQ impact is proportional to how much transport activity there is, how much energy is used per unit of activity, the emissions per unit of energy and a very simplified impact factor, which is determined by how the emissions are dispersed into the atmosphere and how close they are to the population.
So in simplified terms, we can reduce the impact of transport by reducing one of these factors.
For activity…
For energy intensity…
For emissions factors…
For impact…
So today I’m highlighting 3 priorities as I see it, in roughly order of timescale, so from short to longer term priorities.
More efficient engines
Light-weighting
Reduced drag
Low rolling resistance tyres
How close are people to the source of emissions?

4. Caution: Air quality (NO2) in London
NO2 concentrations have not improved even though vehicle emissions standards have become stricter…
EURO 3
EURO 4
EURO 5
EURO 6

5. Priority 1: Real-world emissions compliance
Real-world diesel emissions ~5 times (average) higher than Euro 6 standard
European Commission Real-Driving Emissions limits
Euro 6 ×2.1 (0.168 g/km) from Sep 2017
Euro 6 ×1.5 (0.12 g/km) from 2020
Independent, in-service testing required
O’Driscoll et al Atmospheric Environment 145: 81–91.

6. Consumer information www.equaindex.com
Here is an example of the information that’s open for all of you to look at for the different vehicles tested by Emissions Analytics

7. Priority 2: (Ultra) low emissions vehicles
Range of options to suit passenger/commercial vehicles
Low (potentially zero) tailpipe emissions
EVs make up <2% of new car sales in UK
Hybrid EVs (HEV)
Plug-in hybrid EVs (PHEV)
Battery EV (BEV)
Advanced IC engines
Geofencing
Range-extended EVs
Hydrogen fuel cell EVs
That is ultra low emissions vehicles.
At these early stages, we’re seeing a very large range of technology solutions to meet the specific requirements of different customer needs. In the medium term, I expect they will all have some part to play. These technologies drastically reduce tailpipe emissions, some to zero.
Geofencing is when there is an automatic switch in a vehicle with energy storage to say that the battery power must be used and the range extender engine can be switched on. This could be used around air quality hotspots or in ulta-ultra-low emissions zones.
Natural gas/ biomethane
Zero tailpipe emissions

8. Opportunity: Reduce peak engine load
O’Driscoll et al Atmospheric Environment 145: 81–91.

9. Hybrid trucks HGVs account for ~24% of London NOx emissions
Use electric power to provide ‘boost’ during acceleration

10. Driving behaviour [TRAFFIC SUMULATION VIDEO]
Smoother ‘eco-driving’ benefits
Fuel consumption: up to ~10%
NOx emissions: up to 25-50%

11. Thank you. Dr Marc Stettler
Centre for Transport Studies | Department of Civil and Environmental Engineering Imperial College London
20th April 2017