I think French Busy and UK Busy are a bit different.
I have ridden the B500 on a Sunday and found it reasonably good, a bit busier than in the week, but nothing compared to how any great biking road in the UK gets jammed on a nice sunny weekend.
On my first Alps trip I was warned about how commercial and busy the Julier Pass is, I rode it twice, and both times the traffic was what I would call very light on any A or B road in my part of the world.
Ain't that the truth
, next time I visit her I will defiantly be having a go. 
