Saw this article in the Sydney Morning Herald. Bloody excellent idea.
For motorbikes, there are several grades of licenses you can get, and you can't legally ride the bigger gruntier bikes with the low-level license.
For trucks and buses, you have licenses again, for the different sizes.
For planes, you need to get certified in each and every model you want to be able to fly.
But for cars, we adopt a "one-size-fits-all" approach. This has always struck me as ludicrous; the skills you need to drive a VW Beetle aren't the same as you need for a Saab sports car. Why not have different license types? It just makes sense.
Of course, I think they should also make the rego on urban 4WDs so high as to make them uneconomic, but that's just me... ;)