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Tyres, brake particles under scrutiny
UK looks at cracking down on non-exhaust emissions to reduce health costs
25 May 2018
PARTICULATE emissions from vehicle brakes and tyres are shaping up as the next automotive pollution battleground, starting in the United Kingdom.
The UK government has announced that it will work with international partners to research and develop new standards for tyres and brakes to address toxic non-exhaust emissions of micro-plastics that can pollute air and water.
The crackdown was foreshadowed by environment secretary Michael Grove as part of a Clean Air Strategy to cut air pollution from a wide range of sources over the next 25 years.
The move comes even though wider use of regenerative braking in electrified cars over the next several years appears set to greatly reduce dust from friction brakes.
Regenerative braking employs the magnetic force of the motor/generator to slow the vehicle while recharging the battery, greatly reducing conventional braking force required to stop the vehicle.
For example, the new all-electric Nissan Leaf can be driven in most circumstances with one foot, pressing down on the “E-Pedal” throttle for acceleration and lifting off for braking via the electric powertrain.
The UK government claims that even though air pollution has been greatly reduced in UK cities of recent decades, airborne pollutants are still the fourth largest threat to public health after cancer, obesity and heart disease.
The particulates from brakes and tyres are microscopic, floating in the air and easily penetrating deep into human lungs when breathed in. They can also wash into waterways and enter the food chain via fish and other seafood.
The latest anti-pollution strategy is expected to glove with UK plans to greatly reduce vehicle exhaust emissions by – if leaked documents are to be believed – banning pure combustion engines and making it mandatory for all new cars sold from 2040 to be capable of travelling a minimum of 50 miles (80km) on battery power.
The move has been slammed as reckless by Toyota UK managing director Tony Walker in a speech to British members of parliament, saying the cost of batteries for a plug-in car would price many consumers out of the market.
Toyota is the world’s biggest manufacturer of hybrid vehicles such as the Prius, which can travel only short distances on electricity before the petrol engine kicks in.
Regardless of UK government regulation, sales of electrified vehicles are expected to rise substantially in most markets after 2020, with many manufacturers phasing out diesel and shifting to hybrid and full-electric vehicles.
While the UK currently has only 16,500 EVs on its roads, sales of plug-in cars this year have jumped by 50 per cent. By 2020, the forecast is for a million EVs to be on the roads.
Apart from regenerative braking, brake particulates can be reduced through new-generation discs that greatly reduce wear and abrasion.
Bosch offers such brakes – called iDisk – with a hard tungsten carbide coating that it claims can reduce brake particulate emissions by 90 per cent.
It says the brakes are currently three times more expensive that brakes with iron discs, but they last longer. They are also three times cheaper than top-shelf ceramic discs offered on exotic cars.
Tyre particulate dust is a bit more problematic, with all vehicles running on tyres that emit nano-particles. According to an OEDC report, tyres are the 13th largest source of air pollution in Los Angeles.
The report suggests that road carrying 25,000 vehicles a day can produce up to 9kg of tyre dust per kilometre, some of which has been found in brain tissue.
The UK plan appears to be to work with tyre manufacturers to address this issue, perhaps with new compounds that do not give off micro particles harmful to humans and the environment.
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