London cabs?

Make that cabs in general.

I thought everyone knew that the little orange lights on the corners of cars are just for decoration.

They don't seem to be used for anything else. ;)

Ah, you see, the problem is that people have fallen for the lie that just because it is called an "indicator" that it is supposed to be used to "indicate" something (be it intention or direction), not so. What they are actually for is to assist the vehicle in making certain manoeuvres. If you are part-way around a corner and you doubt that the vehicle can make it all of the way, then you flip this little lever, and the light starts flashing. This flashing, the rapid adding and subtracting of photons, increases the mass on that side of the vehicle, making it just heavy enough to complete the turn.

That must be what they are really for, because that's all they ever seem to be used for.