[Corney]

Corney asked the Naked Scientists:

On some 4x4 off-road vehicles (like Pajero), you get a fancy tail light cluster on the rear but it does not work. Instead there is a less fancy, plain cluster in the bumper that does all the signaling work. Why would it have two sets of tail lights?
   
Thank you and best regards

Corney

What do you think?

[DoctorBeaver]

Rear foglights, possibly?

[techmind]

Some cars have conventional (tungsten-bulb) brake lights at the edges, then a high-level LED-based light. The LED light lasts almost forever, while the conventional bulbs blow after a few years. Lazy drivers who don't replace their dead bulbs end up purely with the LED lamps remaining. I don't know the model of vehicle you describe, but the above scenario is not unusual.

When all the lights are working, you can tell the LED "bulbs" because they come on instantly and fractionally before the filament bulbs (which take a fraction of a second to warm up). LED lamps may also appear a more saturated red, but this is harder to judge. Some manufacturers have claimed that the LEDs are a safety bonus - "think of the extra yards you travelled before the conventional bulbs lit up" etc.

[turnipsock]

I have wondered about this as well.

The vehicles have a full cluster of lights and then they add a second set of brake lights in the bumper.

The glare from too many lights makes it harder to see what is going on. One blown bulb in a four bulb rear can make it hard to work out what is going on.

Loads of rear lights can also make it hard to see brake lights. Its even worse when people turn on fog lights when its hardly foggy...brake lights are virtually obscured.

If the visablity is bad enough to justify rear fog lights on the car in front, its bad enough to justify me driving on full beam and front fog lights.

[qazibasit]

well it depends upon the intensity of brakes. By intensity i meant how much u have pushed the brake if its an emergency brake then all the brake lights will work and glows at the same time.