So......You are obviously fixing a tire and probably in a bad mood. (flat tires do that) Everybody can plainly see that and leave you alone to do your business. Which at the end of your post you specifically ask for anyway. So what's the problem? You want them to ask you a stupid question? "Flat tire, huh?" "Nope, the air got stale in my tires and it needed changing! Here's your sign!"
Next, you didn't paint a good picture of getting run over but it sounds like you were sitting on a curb doing your work. What is a motorist supposed to do? Stop in traffic, get out of their car and politely ask you to move your feet? You can plainly see them too so get out of the way. Parking sucks in most towns anyway and it doesn't help when some dude has his bike scattered all over the place.
If you are looking for incivility, no doubt you will find it. I have had many roadside emergencies on the motorcycle and on the bike and I always get offers of help.