Pedgilante
A person who pursues and stops or impedes another traveler for the purpose of accusing or shaming them for alleged illegal or inconsiderate transportation acts, there by doing the same.
After following the sedan for three blocks, the pedgilante got out of their car at the red light, stepped to the car they had been pursuing, knocked on the window and when rolled down, began to lecture the driver on their speed which was alleged to be above the posted limit. The lecture continued as the pedgiliante stood in the street as the light turned green causing unsafe driving conditions.