That shoulder looks solid (not sure why you're talking about loose gravel, Slim), and probably no more debris strewn than most of the bike lanes in my fair city. I definitely prefer that kind of riding, includings the high speed traffic, to riding narrow roads with no shoulder, no bail out (high berms to both sides) and impatient traffic. Is it risk free? No way. As others have mentioned, the impact of getting hit at 60plus is going to be pretty serious. However, the likelihood of that impact is pretty low, I would think, as long as you can stay to the middle or right of that shoulder.

I would do it (but I agree with folks about the need for bullet proof tires).