What you are describing is tiered energy pricing. This is already done for natural gas and electricity in many areas. The tiered pricing happens because energ

What you are describing is tiered energy pricing. This is already done for natural gas and electricity in many areas. The tiered pricing happens because energy utilities are incentivized via regulation to reduce consumption after a certain point. No such incentive structure exists for the gasoline market, and absent a true carbon tax, the remaining way to achieve conservation of gasoline is to push forward alternatives to gasoline powered vehicles.