the reason I want the separate / independent rear and front, is:
in a convoy / queue and you are last man, you only need the rears on as you are following a guy in front, and as can see him don;t need fronts.
if you first man, then turn on front and off rears as the guy behind will be able to see you. even if all parties are driving at a correct distance.
you don't need to see fogs of the other cars even if on other side of the road, as what idiot would consider overtaking to need to know if more cars in the said convoy
if you look at armed services lorries in convoy they only use front side lights and rear and last fogs.
if vw though bling rather than practicalities they really are dumb, but then designed for euro law with us brits tagged on the side, so could be specific.
highway code link:
http://www.direct.gov.uk/en/TravelAndTransport/Highwaycode/DG_069859
states "may" not must use if fog conditions as well. so all about chice.
particular attention to:
226
You MUST use headlights when visibility is seriously reduced, generally when you cannot see for more than 100 metres (328 feet). You may also use front or rear fog lights but you MUST switch them off when visibility improves (see Rule 236).
[Law RVLR regs 25 & 27]
Fog
234
Before entering fog check your mirrors then slow down. If the word ‘Fog’ is shown on a roadside signal but the road is clear, be prepared for a bank of fog or drifting patchy fog ahead. Even if it seems to be clearing, you can suddenly find yourself in thick fog.
235
When driving in fog you should
* use your lights as required (see Rule 226)
* keep a safe distance behind the vehicle in front. Rear lights can give a false sense of security
* be able to pull up well within the distance you can see clearly. This is particularly important on motorways and dual carriageways, as vehicles are travelling faster
* use your windscreen wipers and demisters
* beware of other drivers not using headlights
* not accelerate to get away from a vehicle which is too close behind you
* check your mirrors before you slow down. Then use your brakes so that your brake lights warn drivers behind you that you are slowing down
* stop in the correct position at a junction with limited visibility and listen for traffic. When you are sure it is safe to emerge, do so positively and do not hesitate in a position that puts you directly in the path of approaching vehicles
236
You MUST NOT use front or rear fog lights unless visibility is seriously reduced (see Rule 226) as they dazzle other road users and can obscure your brake lights. You MUST switch them off when visibility improves.
[Law RVLR regs 25 & 27]