Dear Jakka, 
Thank you for the response. 
If we were to go down that road we'd need to narrow and slightly move the existing highway, mark it as single lane + oneway=yes, draw a second one lane highway for the opposite direction, and add an elongated approx.400mm wide highway between the existing and the newly drawn highways with kerb=lowered and surface=setts;convex;overrijdbaar, plus kerb=further_lowered (but not flush, as that is imperceptible to blind users - see wiki?) where vehicles emerging from drives need to cross.    

Al met al lijkt het dat, until we find many more instances of this type of lane separation, we'll close the note, keep a mental note, and bring the subject up for more formal discussion once we've found hundreds of instances? 