Ah. The ones I see on the highways, have them as DRLs. I dont think I have ever seen one with a full beam there.
Do they serve a purpose? Roof ones, I can see a point. But these ones?
To be honest, the roof spots just bring out the big kid in you
They don't half light up overhanging trees and stuff
In the R460/500 cabs, the roof lights are knocking on for being 13ft in the air, so when you are on a country road with hills and brows, the lights will light up oncoming traffic that you've not seen and dazzle them, so you switch to the lower levels, we still have main beams in the headlights too btw. Handy though when an oncoming car has their bright as the sun LED mains on, just melt their retinas with the roof lights,
Scania USED to, at the customers request, set all 6 main beams to come on at once, but they've instructed their garages to not do it anymore, its done via a laptop.