Route Napolean from Grenoble
 

I'm traveling a section of the Route Napolean and would like opinions on expected drive time between Grenoble and Castellane, including a few quick stops on the way including at least 45 minutes in Sisteron. Is 6 hours about right for a comfortable drive?

thanks in advance

6 hours seem fine but it depends on the season (weather and traffic conditions in winter).

Thanks Pvoyageuse, the trip is in planning and will be early June next year, I assume road conditions will be fine at that time of year?

Yes, of course, I was thinking of mid winter ! :-)

Cheers Pvoyageuse,
Going off topic here, but would you be familiar with the roads of col du galibier and alpe d'huez?

No, sorry :-)