The emission-free vehicle is the human being. Some continental cities are managing to make 50 per cent of their journeys by bicycle (and most of the rest on foot or by public transport) and no one would say that Basel, Freiburg, or Groningen are less pleasant than British cities as a result of extensive works to discourage car use.
Are we ready for this change? Presumably the 150-plus people held to have died as a result of vehicular pollution in four days of December 1991 would vote for it now, if they could.
The main thing is that we recognise transport pollution as a problem whose solution lies only in alternatives to the car, and
not on brilliant technological advances.