EDIT: Original post wattage was wrong.
Single reversing light is sadly quite common in Europe. My last car was the first I had owned that was fitted with a single, 21W reversing light and there was a clear worsening of the light output to the rear. I partially resolved the issue by making a 20W halogen fitting out of a G4 fitting:
, the bayonett base of the original 21W bulb and a 20W, G4 halogen bulb:
Light output was considerably improved. Now I see that there are various aftermarket LED bulbs available, some of which will produce considerably more lumen than the original.
I haven't examined the original fitting, so can't be sure of the type, but it's clear that this is an ordinary, incandescent bulb.
