The advice from Greenpeace and Sadiq Khan is to avoid wood-burning stoves and non-essential driving. They miss what is arguably the chief cause: coercive traffic control. By making us stop, idle and restart, endlessly, needlessly, the system maximises emissions, brake dust and fuel use. As I wrote in this 2007 piece, freedom to filter at low speeds and low revs would cut emissions by 75%. Could the main culprit, which costs lives and costs the earth, be the traffic control system itself?