Another of the differences I have noticed between driving here and back home in North America is that people here only pass on the right (which is like passing on the left at home). This rule took some getting used to, but I was driving so slowly at first that I never accidentally violated it.
I've discovered that this simple rule improves traffic flow significantly. If everyone could only pass on the correct side (right in Britain, left at home), there would surely be fewer accidents. Less experienced drivers would not routinely be faced with drivers suddenly appearing as they try to pull off the road.
The rule makes things easier for everyone. Faster drivers do not have to decide which side to pass; it becomes automatic. Slower drivers do not have to choose which lane to use; they always pull to the slower lanes. When changing lanes, everyone knows whether they are watching for slower cars or faster cars, and they are less likely to be surprised by an unexpected car.
The more I drive this way, the more I realize that it may do a lot more than simply reduce the number of accidents. A rule that you never pass a moving car on the wrong side (left in Britain, right at home) would also cause a lot of traffic jams to melt away. Think about it; if there was no passing on the slow side, then no one would change lanes that way in a traffic jam unless they had to get off the road. With less lane changing, the traffic in each lane would start to move at a more constant speed, which is the first step to clearing a traffic jam.
As an added benefit, cars merging onto the road would no longer rush to the end of the merge lane and try to cut in at the last moment. Since they would not be allowed to pass any of the traffic already on the road, they would have a strong incentive to merge near the beginning of the merge lane. This would help reduce the traffic tie-ups which inevitably seem to happen at the merges, as people reach the end of the merge lane and are forced to come to a stop before merging, instead of merging at the speed of traffic.
Even if the law remains as it is, we can all drive to help improve the traffic. If each of us adopted this "don't pass on the slow side" rule, we would be doing our bit to help smooth out the traffic. Without everybody doing it, perhaps we can't completely slow down when the traffic in the next lane is slow, but we can at least slow somewhat and make things more even.