The extra weight of electric vehicles is often used as a stick with which to beat them when comparing their environmental credentials to those of ICE cars.
Non-exhaust emissions are generally taken to mean tyre wear particles (TWPs) and brake wear particles (BWPs), but can also be taken to include the resuspension of particles on the road.
Received wisdom is that, all thing being equal, the regenerative braking systems used on EVs does much to mitigate BWPs but this is offset by their weight generating more TWPs.
New research however, has found that while in some scenarios that is the case, under the majority of driving conditions electric vehicles generally produce less non-exhaust emissions.
Researchers from the Virginia Tech Transportation Institute began by developing models that would allow them to account for vehicle speed and weight to calculate brake and tire particulate matter emissions.
Using specialist microscopic traffic simulation software, the team compared 24 EVs, ICE, and hybrid vehicles across a variety of weights and sizes. The vehicles were tested over three dynamometer drive cycles, which provide a repeatable driving pattern on a machine that simulates road load conditions.
The three cycles represented were: city driving, highway driving and a high acceleration aggressive driving style.
The team found that the more traffic there was present, the less non-exhaust emissions were created by the EVs. Similarly, when there was less traffic on the road EVs performed worse.
However, overall it was found that EVs become the most environmentally sound option if only 15% of its mileage is in cities.
The research emphasised the benefits of regenerative braking which, instead of using traditional brake pads, a regenerative braking system uses an electric motor to slow the wheel, reducing the amount of abrasion that takes place.
Hesham Rakha , director of Virginia Tech Transportation Institute’s Center of Sustainable Mobility said: ‘The model that we developed proved that battery electric vehicles, in the right conditions, have more environmental advantages. The hope is for this tool to inform strategies that could reduce overall vehicular pollution and promote sustainable transportation solutions.’
Limited access to the research is available here.