Why do some countries drive on the right side of the road and others the left?

She was all the way down the street, on the other side of the road.

They had me at the side of the road now.

A woman's voice called to him from the side of the road.

Being on the wrong side of the road didn't help either.

They drive on the wrong side of the road here.

He worked his way down the right side of the road.

After the war, the new state began making further use of the road.

But sure I have never thought of the road itself.

I park the car on the side of the road.