Bear scripsit:

> It's rather like passing a law that says drive on the left/right
> side of the road; either way works, but the law must be passed anyway
> because it's something that the drivers must agree on and it affects
> the design of the vehicles' control interface.

Historically, left-hand driving derives from horseback riding, where it
was important to mount a horse from its left side, so as not to stab it
with a sword worn on the rider's left.  Given that, it made sense for the
left side of the horse to be at the edge of the road, not in the middle.
People wore swords on the left so they could be drawn easily with the
right hand, so ultimately left-hand driving derives from human majority
right-handedness.  In addition, horses have mostly monocular vision and
can spook if approached from the wrong side, so a standard is essential.

Wagons pulled by teams tended to stay to the right, however, because
before the use of driver's seats, the driver sat on the left rear horse.
(Mounting the right rear horse would require standing between the horses,
never a good idea.)  Napoleon's supply wagons spread right driving to
much of Europe, and in early 20th century Spain, many cities had left
driving, while the rule in the countryside was right driving.

Today there are countries where "wrong-side" cars are quite commonly used;
indeed, Samoa recently changed from right driving to left driving because
there were so many wrong-side cars imported more cheaply from Japan and
Australia.  In at least one case, the rule of the road became politicized:
during the temporary occupation of the Falklands by Argentina, right
driving was imposed by the authorities, but many locals continued to
drive on the left as a protest.

See <http://en.wikipedia.org/wiki/Right-_and_left-hand_traffic> for details.

--
John Cowan          http://www.ccil.org/~cowan        cowan@ccil.org
"Your honour puts yourself to much trouble correcting my English and
doubtless the final letter will be much better literature; but it will
go from me Mukherji to him Bannerji, and he Bannerji will understand it a
great deal better as I Mukherji write it than as your honour corrects it."
        --19th-century Indian civil servant to his British superior

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