Cars are getting bigger, not just through engineering or road safety design features, but because of public popularity.

It may seem that we are influenced by American popular culture. The US has always enjoyed large cars, not least the SUV. Like many other influences that have crossed the Atlantic, often through film and television, we are choosing to buy bigger and bigger vehicles.

Growing problems

Problems gave already been raised when it comes to regulations governing the size of parking spaces. Few cars can fit in bays, not if you want to actually get out of the doors once you’ve parked up. There have been other warning about the weight of bigger cars and EVs. Can multi-storey car parks, designed according to building regulations set many decades ago, actually cope with the increasing weight?

Now another issue is grabbing the headlines, as covered by a new article from The Guardian.

Increasing roadside pollution levels are being blamed on “car bloat”.

‘Tiny particles from the wear of vehicle brakes, tyres and roads already make up about half of the air pollution particles from traffic. This will be getting worse because our car fleet is getting heavier and there are no clear policies to control this pollution source.’

The article continues: ‘The issue known as “car bloat” and “autobesity” refers to vehicles bought today being bigger than the ones they replace. This affects parking and raises concerns about safety for other road users. A US study showed that children were eight times more likely to die when struck by an SUV compared with a normal passenger car. Bigger vehicles also have a greater impact on the climate and air pollution.’

Over sized

According to the report, European car weight has increase around 9% on average. The sales of ‘small SUVs increased by five times and large SUVs sales increased by seven times’.
Of course with this increase in weight comes more pollution. Not only do they require more power to accelerate and cruise, so more fuel, but they require more power to stop and even corner.
Particles from brakes,  tyres and road surface are now regarded as a serious and growing issue when it comes to roadside pollution and human health.

‘Several toxicological studies point to potential damage to health from breathing brake, road and tyre pollution, but there are still many important knowledge gaps, not least around brake wear and particles from electric vehicles.’

A new study by Dr William Hicks and his team, from Imperial College London, has been carrying out more research into the issues. Computer simulations are being used to understand the findings. ‘ In his latest study, six different vehicles undertook simulated drives around London and an international standard vehicle test.’

Stopping the rise

The results. show that the brakes in the large SUV work twice as hard as those in the small compact car. Batteries in electric vehicles typically make them 20% heavier than their petrol and diesel equivalents.

However, regenerative braking in EVs and hybrids can actually reduce pollution issues. They use their electric motors to slow down, and only use their friction brakes during hard and slow-speed braking.

‘Despite their additional weight, the brakes in the battery and hybrid vehicles worked less than their petrol and diesel equivalents. Brake pollution was reduced by 88% in the international driving test and 68% in the London test.

This is another plus point for choosing to go electric, despite the weight gain. However, it is not just the vehicles that are to blame for pollution problems.

“I was also surprised by the extent to which driving styles can influence brake-wear emissions,” says Hicks. “Aggressive driving and braking, which is common in city driving, causes more direct abrasion between disc and pad, but also heats the brakes up, causing more ultrafine particle emissions too.”

“In the long term, smart traffic-control and driver feedback should encourage efficient driving. But in the short term, individual drivers can reduce air pollution by driving smoothly. This could be encouraged through traffic calming measures (20 mph speed limits should help), media campaigns and driver awareness courses.”

Technological test

All vehicle pollution levels are affected by weight, with large lorries and buses cited as urban issues.

There are technological solutions in developments, but are yet to be widely adopted. However, going forward, these interventions could be a significant way to improve urban air quality.

You can read the full article here.