With some highly selective reporting based on a recent paper prepared for the Organisation for Economic Co-Operation and Development (OECD), an article in the ‘Times’ dated of Dec 7th 2020 turned out to be no more than a blatant and misleading attempt to discredit Electric Motoring by alleging that tyre and brake particles were worse than in the case of internal combustion engine vehicles.
They wrote, “While switching to electric cars will remove pollutants from exhausts, models with large batteries capable of travelling 300 miles between charges emit up to 8% more fine particles from tyres and road wear than petrol and diesel cars.” and called for Electric Vehicles no longer to be exempt from “tolls and congestion charges aimed at reducing road traffic emissions”.
However the electic vehicles (EVs) emitting “up to 8% more fine particles” were light commercial vehicles and SUVs with battery capacity enabling 300 km travel before recharging. The 300 km range (themselves top-of the range vehicles) only produce an additional 3.6% more of the 2.5 micron particles and the figure given for the 10 micron particles is a reduction of 6.5%. In fact, when these larger (but still damaging) particles are considered – .
The OECD Report is detailed but perhaps a little ahead (or behind?) its time since it is quite open that there is a need for more practical work to be carried out on tyres, the wearing of road surfaces and the role of dust thrown up from the road by passing vehicles. They are also quite clear that they have estimated tyre wear based on assumptions about vehicle weight, rather than making any measurements.
This is one problem about the study. It is known that tyre wear and particles increase as the vehicles get heavier – and at the moment the batteries make EVs heavier than their petrol driven equivalents. However the authors have made estimates about the battery weights which are out of date. They have used a figure of 10 kg/kWh of capacity, when in reality it’s already below half of that. So it makes the electric vehicles in their study much too heavy and consequently over-estimates the tyre wear particles that will be generated. Not only that, but they don’t take into account that new developments mean that by 2030 EVs will be much lighter still. So that makes their future predictions of the numbers of particles over-estimates as well.
The second problem is that the survey also includes road dust – which hasn’t got much to do with how the car is powered anyway – and much of the data relates to California, where the air is drier and battery powered SUVs exist in far greater numbers than in Europe, where they are almost unknown.
Sorry, ‘Times’ – if you want to continue your crusade against the Congestion and Low Emission Charging Zones in London, you’ll have to your homework more thoroughly. Better still, though, if you were to campaign positively for cleaner air in all our major cities!