Everybody seems to be getting hung up on the size, mass or height of the vehicle. While that may be why they've been targeted it's certainly a convenient catch all to get across the point, which most on here seem to be missing. The crux of the issue is transport efficiency, or 'insert toxic gas here' per mile produced. Whether co2 or Nox etc. Small cars produce less. Yes a modern big SUV probably produces less than a 10 year old hatchback but it definitely produces more than a hatchback of the same manufacturing year. This action is raising awareness of this fact and asking what cost does personal convenience truly come with. Could you switch to a more economical car, whether that be newer or smaller? And yes, before people assume, I am a motorist.