* Historical precedence and established road systems: Many countries adopted a left-hand driving system early on, often influenced by factors like the dominant direction of horse-drawn traffic or the way agricultural implements were operated. Once a standard was established, it became extremely difficult and costly to change. This is why many countries, including the UK, Japan, Australia, and India (among others), stick to left-hand driving and right-side steering wheels.
* Passing on narrow roads/Overtaking: Left-hand driving systems make overtaking on narrow, single-track roads safer in some scenarios. With the driver on the left, they have a better view of oncoming traffic. Similarly, right-hand driving systems offer similar advantages in different situations.
* Infrastructure: Once a country establishes a left or right-hand driving system, much of the infrastructure (roads, bridges, roundabouts etc) is designed around it. Switching would necessitate a massive and disruptive overhaul.
* Practical considerations: In some cases, especially historically, certain aspects of vehicle design and manufacturing may have been influenced by local conditions, further cementing the existing system.
In short, it's not a simple choice, but rather a complex interplay of historical conventions, road design, safety considerations, and the substantial costs of changing established infrastructure and societal habits. The current distribution of left-hand and right-hand driving reflects these historical processes and their long-lasting effects.
