Mount Washington auto road? Two words..
There will be crowds all day long
Be prepared for extreme weather changes..it can be sunny and seventy degrees at the bottom of the rock pile and foggy with freezing rain at the top..check conditions BEFORE you pay.
Be sure your brakes are in order.. lower the gear the better up or down
The further up you get the more pull offs there are.. good if you have some kamikaze idiot behind you..don't get frustrated pull over and let the asswipe by.
Don't forget your camera
Much of the road is paved and what isn't is hard packed. It is not a particularly hard road to ride..use common sense and you will be fine.