We ride amongst the barbarians as well. Several years ago we were moving some garden implements across town. It was amazing how much more space motorists gave my wife and I when we had shovels, hoes and rakes in our left hands.
I actually think what was happening is that there is so much to pay attention to while driving that most people just focus on those things that pose a threat to them like other motor vehicles. The rakes and such just elevated us to the level of threat and the motorists behaved accordingly.