Greg Hennessy wrote:

It's neither voluntary or progressive.

Of course it's voluntary: if you don' want to pay the higher charge,
get a smaller car.

About as practical as telling someone to get a smaller house if they don't
want to end up paying more council tax.

Not really. They don't have to get a smaller car - just a more
efficient one.

It more like saying - "if you don't like your heating bills, get more
insulation - not neccessarily a smaller house.