Older cars in urban areas less to blame for harmful emissions

Issue date: 16 November 2017

Research for the RAC Foundation has added weight to the argument that scrapping the oldest cars owned by people living in towns and cities would have negligible effect on air quality.

The air quality and emissions analysis work has been led by Dr Tim Chatterton from the Air Quality Management Resource Centre at the University of the West of England (UWE Bristol).

Unique analysis of MOT information for 22 million individual cars has enabled a team of academics – led by Professor Jillian Anable of the University of Leeds - to use mileage, emissions and registered keeper data to map exactly where the highest polluting vehicles are kept.

The study has shown that areas containing vehicles responsible for emitting the most air pollution (on both a per kilometre basis and over a year due to the distance they have driven) tend to be licensed at locations outside the most-populous, relatively-deprived urban areas hardest hit by harmful emissions.

Conversely, the most polluted areas tend to contain older but cleaner cars. Where older vehicles are registered in towns and cities they are likely to be driven less far and therefore produce, overall, relatively small amounts of NOx, PM and CO2. The research presented in the report highlights that the amount that vehicles are used tends to be considerably more important in determining the annual emissions they generate than their per kilometre emissions.

The report – MOToring along: The lives of cars seen through licensing and test data – is explicit:

“Areas with a higher proportion of households in poverty experience higher than average levels of pollution, but are responsible for emitting lower than average amounts of pollution.”

The reports adds that the older a car is the more likely it is to be a (less polluting) petrol rather than diesel model, and whatever the fuel type it will tend to do significantly less mileage than newer vehicles.

Mileage category % that are diesel-fuelled

Private cars doing less than 5,000 miles per year 11

Private cars doing between 5,000 and 12,000 miles per year 25

Private cars doing more than 12,000 miles per year 49

Steve Gooding, director of the RAC Foundation, said, “The message is crystal clear. Targeting a scrappage scheme at the owners of old diesel cars in the most polluted areas is a waste of time. Poor air quality is a product of relatively new vehicles – not just cars, but taxis and vans – entering our urban areas from outside and doing high mileages.

“This report also confirms that those on the lowest incomes are likely to have the oldest cars but reveals that more often than not they will be petrol rather than diesel. Intuitively this must be true, given that diesels only make up about a third of the total UK vehicle fleet and most of them will have been bought relatively recently.”

Dr Tim Chatterton from UWE Bristol, said, “It is time that UK air pollution policy stopped focussing solely on per kilometre emissions from the vehicle fleet, and began to consider serious options for enabling less traffic on our urban roads. This would have benefits not just in terms of better air quality, but also in reducing noise, improving road safety and public space and quality of life more generally.”

The research also reveals that:

• Inequalities in the financial costs of motoring, with greater proportions of income being spent on motoring in low income areas.

• Strong, but as yet unexplained, spatial patterns in terms of average car age, with the north of England, Scotland and South Wales showing a tendency for the registered car fleet to be younger on average.

It suggests that further analysis of vehicle-specific MOT data could produce insights into areas such as:

• The rate of uptake of new versus second hand vehicles and how this pattern changes in different areas of the country.

• Patterns of uptake of electric vehicles over time, including their spread through the second-hand market both spatially and over time, and with respect to the intensity of their use.

• The responses of vehicle owners to planned Clean Air Zones.

The report is available to download

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