Regarding driving on the left or right: I find that there can be lots of variance - even especially within the United States - regarding how to treat traffic signals.

In many places - Phoenix area comes to mind - Green means go, Yellow means speed up, and Red means next 2 cars can go. In other places, Yellow means slam on your brakes. (This just comes to mind, but I wonder if there's a difference in traffic codes regarding it being legal to enter the intersection on a yellow light, and being legal to be in an intersection when the light turns red. Anyone?)

I also find wide differences in motorists' habits when the light turns green. In some places - Bay Area comes to mind, as well as L.A. - you had better have the foot on the accelerator the moment the light turns green, or suffer The Horn. In other places - like the Pacific Northwest - a Green light means that one should disengage the emergency brake, perhaps start the engine, take a sip of coffee, ensure the intersection is clear, and then proceed. This is especially puzzling in Oregon and Washington, where motorists are usually so good about stopping at Yellow lights (see paragraph above), so you end up with a good 10 seconds where there is just NO activity in the intersection.