With regards to road tax, it should be based on engine size, not emissions. This would be a far fairer system than the current 1, where needlessly large engined cars' tax is based on an emissions reading which is unachievable in real life. Ideally, there should be no tax discount for diesels, hybrids, or electric cars, plus there should be an equivalency formula for turbocharged petrol engined cars.
With regards to ALL car emissions, the EU needs to create a more realistic test to measure the emissions from all cars, then use this to work out how unachievable in the real world their current, ridiculous targets are, and then decide on more realistic emissions targets. I completely agree that all emissions need to constantly be reduced, but the current regs are too unrealistic and as such, far to open to abuse by manufacturers.