Question: what do the following statistics have in common?

Answer: the vehicles on our streets, primarily the not-so-humble passenger car.

Despite the (slow) migration to electric-powered cars, consumer trends are making driving even more wasteful and unequal. A recent analysis found the emissions saved from electric cars have been more than cancelled out by the increase in gas-guzzling Sport Utility Vehicles (SUVs). Around the world, SUVs alone emit more carbon pollution than Canada or Germany, and are causing a bigger increase in climate pollution than heavy industry.

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While cars are sometimes necessary for people’s mobility and social inclusion needs – not least those with disabilities – car-centric cities particularly disadvantage the already-marginalised. In the UK, women, young and older people, those from minority communities and disabled people are concentrated in the lowest-income households, of which 40% do not have a car. In contrast, nearly 90% of the highest-income households own at least one car.

So the driving habits of a minority impose high costs on society, and this is especially true in cities. Copenhagen, for example, has calculated that whereas each kilometre cycled benefits society to the tune of €0.64 (53 pence), each kilometre driven incurs a net loss of -€0.71 (-59p), when impacts on individual wellbeing (physical and mental health, accidents, traffic) and the environment (climate, air and noise pollution) are accounted for. So each kilometre travelled where a car is replaced by a bicycle generates €1.35 (£1.12) of social benefits – of which only a few cents would be saved by switching from a fossil-fuelled to an electric-powered car, according to this analysis.

Reducing car use in cities

Half a century ago, the Danish capital was dominated by cars. But following grassroots campaigns to change policies and streets, including replacing car parking with safe, separated bike lanes, Copenhagen has increased its biking share of all trips from 10% in 1970 to 35% today. In 2016, for the first time, more bicycles than cars made journeys around the city over the course of that year.

But while many other car-limiting initiatives have been attempted around the world, city officials, planners and citizens still do not have a clear, evidence-based way to reduce car use in cities. Our latest research, carried out with Paula Kuss at the Lund University Centre for Sustainability Studies and published in Case Studies on Transport Policy, seeks to address this by quantifying the effectiveness of different initiatives to reduce urban car use.

Our study ranks the 12 most effective measures that European cities have introduced in recent decades, based on real-world data on innovations ranging from the “carrot” of bike and walk-to-work schemes to the “stick” of removing free parking. The ranking reflects cities’ successes not only in terms of measurable reductions in car use, but in achieving improved quality of life and sustainable mobility for their residents.

In all, we have screened nearly 800 peer-reviewed reports and case studies from throughout Europe, published since 2010, seeking those that quantified where and how cities had successfully reduced car use. The most effective measures, according to our review, are introducing a congestion charge, which reduces urban car levels by anywhere from 12% to 33%, and creating car-free streets and separated bike lanes, which has been found to lower car use in city centres by up to 20%. Our full ranking of the top 12 car-reducing measures is summarised in this table:

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