When you have been involved in as much mobility discussion as we have, you tend to hear a few statistics bandied about. Sure, we all have a tendency to interpret information in a way that confirms our pre-existing belief but for those wanting to combat confirmation bias and to make decisions based on nuanced reality, rather than convenient rhetoric, we have dug behind several oft-repeated headlines around urban mobility and rooted around for the reality.

Myth:
30% of traffic is searching for parking
Reality:
In 2013 the San Francisco Municipal Transportation Agency reported that 30% of traffic in the city was searching for parking. The statistic emerged in the book The High Cost of Free Parking in which its author Donald Shoup took 16 studies conducted between 1927 and 2001 from across the world and calculated from that, on average, 30% of the cars in congested downtown traffic were cruising for parking. One of the studies – held in Freiburg, Germany in 1977 – recorded an astonishing 77% of cars were searching for parking. The most recent study included was undertaken in New York in 1993 which found that 8% of traffic was searching for parking. Never mind the reliability of the source data, the value of averaging across global cities over a period of 75 years and then applying it to today as a general rule, should at least raise an eyebrow.

Myth:
In the UK, 40,000 deaths a year are caused by air pollution
Reality:
Given that nobody has air pollution written as the cause of death on their death certificate, how is it possible to count the number of deaths? A report from the Royal College of Physicians in 2016 attempted to model the number of fatalities caused by air pollution by inferring the increased risk of illness caused by particulates in the atmosphere to air quality and population statistics. As this correlation gained a foothold in the popular imagination Professor David Spiegelhalter, from the Winton Centre for Risk and Evidence Communication at the University of Cambridge, pointed out that according to the body on whose statistics the calculation was based, the figure could actually be anything between 5,000 to 60,000. The professor also added the following caveat: ‘The World Health Organisation, using a different methodology, estimate only 16,000 attributable deaths in the UK from air pollution’. As every school science teacher reminds us, correlation does not imply causation and computer models are built on human assumptions.

Myth:
Air pollution is worse in London than Beijing
Reality:
In early 2017 newspaper articles reported that air pollution was higher in London than in Beijing and indeed for two days in the British capital, the Air Quality Index (AQI) had particulate levels a bit higher than in Beijing. The spike was attributed to the calm weather in London, which meant that the pollution was not dispersed as usual. But this was highly unusual. Indeed for most of the week in which the spike occurred the level in Beijing was about three times higher than in London. The level was four times higher than London in the Chinese city’s industrial outskirts. Generally, figures collected by the World Health Organization show that Beijing’s levels of particulate pollution are about five times worse than in London. In the UK, overall emissions of all types of air pollution have fallen dramatically since 1970.

Myth:
Drivers spend four days a year looking for parking
Reality:
This first appeared in a story in the Daily Telegraph in 2017 and has been oft repeated since. It is an extrapolation of an online survey of 2,000 adults in the UK, conducted on behalf of the British Parking Association. Respondents were first asked what frustrated them most about parking and then how long it takes to find parking. From this unscientific poll using self-reported estimations from memory of something we are likely to exaggerate an average of 6 minutes was arrived at. Even if it was accurate, it should be pointed out that by a similar process of extrapolation we spend – on average – 7 days a year on the toilet.