Another question that always has nagged at me was why the Brits always drive on the left side of the road (for the record, even though I said "Europe" in the title, the fact is most of Europe drives on the right like us), but we Americans drive on the right.
Now, I'm really not sure about the Brits. I had to do a little research on this one because it was so perplexing, and all I really got for them was something about knights and swords. Needless to say, no conclusions reached.
I had luck with America, though. As British colonies, we started out driving our buggies on the left just like the motherland. However, in the 1790's things started to change, with the establishment of right-side driving on the Lancaster and Philadelphia turnpike. Many say that America simply wanted to cut all ties with the British and drive on the opposite side. I say similarities in traffic direction is not much of a tie, and I therefore declare BS on that theory.
After research, however, I did find that the Lancaster and Philadelphia turnpike was a privately owned and constructed road. This coupled with the road's distinction as making the first direction change hardly seemed a coincidence to me, so I looked up traveling modes in that time period and found that most agricultural goods (which was the majority of travel on the turnpike) were transported via large wagons with no drivers seat. The driver would sit on the left rear horse in order to keep his right arm free to lash the team (since most people were and are righties), and thus found it useful to drive on the right side of the road.
So what does this have to do with economics? Well, I'm willing to bet that people putting down the kind of bucks required to build a turnpike weren't stupid. And I bet they knew the majority of their customers would be farmers, or transporters of farmers' goods. Put simply, they wanted to cater to their customers, as all good businessmen do-especially the customers who keep using the service over and over again-sometimes called repeat customers-very valuable to any operation.
Thus, the turnpike owners decided it would be best to have people drive on the right side of the road. And I would also surmise that other builders of roads found the same advantages discovered on the L & P turnpike and followed suit (including gov't). Realistically speaking, most of the travel done at that time was for commercial purposes anyway. People simply didn't travel, so most of the road traffic was agricultural of some sort.
Why do we still drive on the right? Beats me. Probably because of good old Henry Ford, who declared early on that his famous Model-T's would only have steering wheels on the left, for which it makes more sense to drive on the right. Either that or changing direction nationally might be a tad difficult. I mean, you'd probably have to ask Congress first. And then all the local governments would have to tear down all traffic signs and traffic lights. Plus, with all of our fancy steering-wheel-on-the-left cars, it could make for tough passing. I guess we could, theoretically, change. Your choice. Ha. Just kidding.