This is a question that I remember hearing a few years ago: If the law were changed so that traffic in Great Britain travelled on the righthand side of the road instead of on the left, would the length of the day increase, decrease or be unaltered? I remember the answer was increase but not by much. The assumed that there is as much traffic west-east as east-west. Changing from left to right side of the road means that the west-east traffic moves a bit further away from the earth axis, the east-west traffic moves a bit closer (because generally the north is closer to the axis than the south). The person that told me this then claimed that this meant that the angular momentum of all traffic increases. (and therefore the day becomes longer due to conservation of angular momentum) My question is: why does the two directions not cancel out? and therefore the length of day would remain the same?