Originally Posted by Helmet Head

One more thing. A really good habit to have is: Never pass on the right.
This is particularly important at any place where the car can and might turn right, but, in order to make it instinctive I think it's better to follow the simple version of that rule, and almost never do it.

The typical situation is that you're near the right side approaching an intersection where cars are passing you on the left who are going straight, when, suddenly, one of them slows a bit (in order to turn right), and before you even realize what's happening, you're catching up and passing them.

So the goal is to develop an instinctive repulsion to passing on the right such that you find yourself slowing down, looking back and probably even merging left before you realize what's happening. If you don't develop such an instinctive repulsion to passing on the right, then you will inevitably find yourself passing someone on the right before you realize what's happening, which sounds like what happened to your husband.