Stu, It's been awhile since I've been involved in one, but there is a lot of planning that has to go into them. Safe areas for pulling over, escape routes (there has to be a way for vehicles to avoid it), systematic vehicles through the checkpoint (you can't pull everyone over; its more like pulling 10 vehicles in at a time, allow traffic to continue to flow and then pull 10 more in once the first 10 are done), flyers to be handed out, media involvement, etc. I'm sure there are Google searches that can be done that will outline more details, but these are off the top of my head from working them years ago.