If I’m sitting around outside at a cafe or a pub or restaurant or whatever, or sometimes when I’m cycling into work I’m struck by the amount of road space cars take up, both parked and moving and have often wondered how much space in London is taken up by cars. Well today I wondered it over lunch time and decided to make a stab at a Fermi estimate:

• London population 8278251 (wikipedia)
• Households with cars 62% (mayors website)
• Average household size 2.3 (census data)
• So number of households in London = 3599239.57
• So 62% of households = 2231528.53. This is the number households in London owning at least one car (not including commercial vehicles, taxis, busses etc.)
• small car dimensions (VW polo) 3.9 m x 1.9 m = 7.41 m² (Parkers)
• large ‘car’ dimensions (Volvo XC 90) 4.8m x 2.1m = 10.08 m² (parkers)

So total area of cars in London if a VW Polo is the average size car = 7.41 x 2231528.53 = 16535626.4073 m²
… and if Volvo XC90 is average = 10.08 x 2231528.53 = 22493807.5824 m²

So the amount of space cars in London take up is somewhere around 16.5km² - 22.5km².

I reckon I’ve been quite conservative here. I’ve assumed that no households own more than one car, I haven’t accounted for commercial vehicles and I’ve assumed that the amount of space taken up by a car is limited to it’s physical dimensions ignoring related car paraphernalia and sub-optimal parking arrangements.

To put those figures in context, Hyde park is 1.4km² and the island of Nauru, home to 9000 or so people is about 21km².

What would you do with all that space?