Can I set it to the speed limit + 9?
I hear the highway patrol say “9 your fine, 10 you’re mine”
That may be true....my last ticket was 66 in a 55 - meanwhile, I steamed past a number of Virginia troopers (NC to DC) doing 77-78 in a 70 - no problem.
In town, however, I don’t think you get +9 - say, in a 35 mph zone.
10% of the posted limit seems to be the rule.