I am really hessitant to be in favor of government imposed bans.   
And so many questions:
If a whole country goes to electric, how can their power grid meet that demand?
What fuel powers the power grid?
Is nuclear the answer?
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I was going to say I don't support diesel being banned if their is an option to leave it...but then read about the NO2. That doesnt sound good. 
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And are electric buses efficient or economical? I didnt realize that our technology and engineering had succeeded in scaling to bus level.
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I don't think existing combustion engine cars should ever be banned. They should all be allowed to be used for their full service life, including rebuilds.  Those used cars are the cars the poor can afford. If you remove them from the market, the poor will be pushed into ever greater dependance upon the state for assistance and transportation. 
PLUS, the production 'harm' has already been done for every car on the road. All of the energy consumption, polution produced as a byproduct of production, and all....has already been paid.   I think it is better to let these cars run their full life before requiring another [energy and resource input, polution and toxic waste byproduct] formation per unit.
That's my thought anyway!!
✌Cents!
Peace!!