No country really needs to switch — it's a matter of comparing costs versus benefits. There is some evidence that left hand traffic is safer despite being less

No country really needs to switch — it's a matter of comparing costs versus benefits. There is some evidence that left hand traffic is safer despite being less common. I don't think the world will ever be all one direction: the cost of changing the larger countries (China, India, Japan, the US) over would prohibit a mass change either way.