Driving on the wrong side of the road. Most people are right handed, so they passed oncoming traffic on the left so that they had their right hand free to either defend themselves or shake hands with their right hands.

According to custom long ago, only those who carried weapons and expected (wanted) a fight went to the left, to present their weapons to oncoming traffic.

Those who just want to pass peaceably went to the right, to keep their shield (if they had one) between themselves and those approaching, or at least NOT to give the impression that they had a weapon ready for a fight.

The reason the Brits continued going to the left is because they've always been the most persistently and consitently offensive people as a culture.

(So I've been told.)

In the US, traffic lights often are "synchronized" so that they work pretty well, at least in high traffic areas. The "Four Way Stop Signs" are less efficient, but work fairly well in low traffic areas.

The WORST OF ALL for slowing down traffic flow are the "Traffic Circles" that are an artifact in a few places but "something new" in most of the US. Here, where the new ones have appeared, the circles are too small for smooth entry/merging/exit since they're dropped into places with insufficient space for a "real circle." They're claimed to be cheaper than lights/signs and require less mainenance, but as used they really clog things up and produce a lot of accidents.

John