Since 2011 Beijing has controlled traffic growth by allocating new licence plates in a bimonthly lottery. There is less than a one in 500 chance of getting a plate in each draw but winning might not be as wonderful as it first seems.

The impact of increased motorised travel extend beyond air pollution. In the UK the total distance walked each year dropped by 30% between 1995 and 2013, and the distance cycled in England and Wales in 2012 was just 20% of that in 1952 – but these changes have been slow and are difficult to study.

In Beijing, predictably, winners took fewer journeys on public transport and walked less than those that stayed on the waiting list. Overall there was no weight difference between the two groups, but this was not the case for the older people. After five years, winners over 50 had about 30 minutes less physical activity per day and were, on average, 10kg heavier.

Elsewhere, Colombian men in households with motor vehicles weighed about 10kg more in those without, and Europeans who cycle daily weigh about 3.3kg less than those who drive.

A long-term resolution to leave the car at home could help the environment, your wallet and your waistline.