Vehicle lighting (headlamps, fog lamps, tail lights, and especially directional bulbs) is more important than most people realize. In the US, we're so used to options on the shelf that when we see a blue-looking headlamp at AutoZone and the manufacturer tells us it'll allow us to see better at night, we take the info at face value, and buy the lamp, thinking we look cool with blue-ish headlamps.
There's also the issue of use: today, on my way to work, it was raining hard and there was a lot of mist & fog in the air, such that visibility was down below 50 feet or so. There were many people who didn't even have their tail lights on, let alone fog lamps. So if you were driving and a person stopped suddenly in front of you, you may not have even known they were there until you saw their brake lights, and by then it would be too late if you were unknowingly following too closely. Unfortunately, fog lamps are used as an odd fashion statement here: "hey, my vehicle came with these cool extra lights, so I'm going to use them!" This is particularly a problem with pickup truck owners: they're already too high up, and have fog lamps, so instead of using their low beams, they use their parking lights (big no-no) and fog lamps. Simply odd; not sure where pickup truck drivers learned this or why they do it, but it's dangerous as almost no one sees your fog lamps, particularly not anyone behind you or directly in front of you.
Then there's directional bulbs. Of course, many people don't even use them when they should. But they cast a wide beam and have little in the way of glare (when they are yellow - fashionable white or red tail lamps are just a bad idea). As such, they should always be used as appropriate.
In Europe, lighting regulations are much more strict. In many countries, all vehicles come with fog lamps, and you can be fined for using them outside of the normal use. My 2002 Mercedes-Benz E320 comes with a rear fog lamp, which some Audis and Volvos also have here in the States (BMW has opted not to include rear fog lamps in their US inventory). The rear fog lamp on the Benz lights up on the driver's side tail light assembly, so an approaching car knows which side of the car they may hit if they approach too quickly, and can effectively maneuver to the appropriate side.
There's an entire science behind vehicle lighting and its effects on the eyes, as well as its effectiveness in certain situations, which depends on which area of the country you live, etc. Daniel Stern Lighting Consultancy & Supply was recommend to me on a Benz board a while back, and Daniel has been great to work with & buy from. He gives his time via email to explain to you what types of bulbs one should use depending on your car and in which area of the country you live. Drop him a line if you're shopping for lighting.
Click here for Daniel Stern Lighting Consultancy and Supply