Answer: Swords

Although the majority of countries in the world drive on the right hand side of the road (that is, traffic flows so that forward traffic moves on the right side of the road and oncoming traffic moves towards the driver on the left hand side of the road), quite a few countries (notably England and prior British territories) still practice left hand driving where the forward traffic is on the left side of the road with oncoming traffic on the right.

To see why this arrangement persists to the present, we need to travel into the distant past. Centuries ago, when populations were armed and swords were the primary weapon, both travelers on foot and on horseback rode so that their dominant arm (the right arm for most of the population) was facing anyone who would approach them on the road.  By walking and riding on the left side of the road, they could draw their sword across their body and present the blade towards the middle of the lane. If they walked on the right side of the road, they would draw the sword and present it to the far right edge of the road.

Although various influences over the centuries have chipped away at this left-hand pattern of travel (such as the advent of horse drawn carriages wherein the rider would sit on the left side of the carriage to make it easier to swing the whip towards the center where the horses were), the cost of switching has deterred England from changing its ways.