I'm confused by what you mean by reduction in safety.
Fuel Duty can more than cover pollution issues and alternative fuels.
VED can then be used to cover police, ambulance, road building.
In fact, VED may need to go up a bit, while Fuel Duty drops as VED has to cover more than Fuel Duty (fuel duty only should cover issues caused by burning fuel, VED should cover issues due to driving a car).
This way, when we have 100% renewable sources of energy for car, we can scrap fuel duty as there is no longer a need for it.
As for over-spending and cuts, we need to save 150bn a year compared to now ... I fail to see how this is such a hard job, as you can easily save £15bn within the NHS, 30bn within Work and Pensions, 15bn within Defence, money within Scottish government (ie removing devolution and the extra layer it adds), and so on.