While someone has already mentioned a tank, its price tag puts it out of reach for the vast majority of the motoring public. The legions of unwashed plebs are Sempletons(pun fully intended) who require a far more economical option, so I present to you the Bob Semple "tank"
An "armoured" superstructure to protect from the chaos a total lack of traffic regulation would produce. Its cheap and shoddyhomemade nature allows for easy DIY fixing on the fly, rather than having to be sent to some workshop or depot. No murder? Remove all the guns or install dummies in their place then, to hang your laundry fromspook everyoneput the fear of God into all those other wankers. Last but not least, low speed and reliability for maximum obnoxiousness towards everyone behind you on the road.