Diesel vehicles produce particulate which is hazardous to health when significant quantities have been ingested. They and petrol vehicles both produce carbon monoxide and other environmental nasties. It is rational to introduce price signals to modify behaviour that is injurious to health and welfare and governments have done this for decades. So why the proposal to tax something that is environmentally better than the alternative, such as energy efficient electric/hybrid vehicles? Since the justification is apparently that all vehicles should be treated equally to fund repairs, maintenance and new road construction, why doesn’t the transport industry ‘pay its way’ when its competition, the railway system, is forced to. Sounds like vested interests – doesn’t it? What do you think?