This is taken from Sammo on the .net (Netmag) Forum from a year or so ago. I agree with it and I can't wait until I get to the Monster Truck stage:

I reckon you should have to earn your way up through the transport strata. You know:

  • socks on polished floors
  • skateboard
  • Rayleigh chopper
  • mobilette
  • scooter
  • milk float
  • reliant robin
  • <100 hp car
  • ice cream van
  • >100 hp car
  • tractor
  • family saloon
  • monster truck
  • harrier
  • space shuttle