I see that you create an homogeneous group of cars based on the odometer. Could you use the quantity of energy used instead.
Basically living in Germany I can enjoy the power and the torque of my car more of those that are bound to speed limits. Of course this will imply higher consumptions and more frequent recharges.
Probably considering the regeneration as well will be more complicated but probably the enrgy used coudl be already a good approximation fro a different groups of cars.
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