It was a twinned highway, yeah. "Highway" in the American sense is nearly always a twinned road, with a barrier in between the lanes. Like, say, the 401 across Ontario.

I wouldn't go over, say, 65 at most, on a highway that didn't have some sort of barrier and one-direction traffic. And this would be 65 in the middle of the night on a deserted road. I agree in that sense his speed would have been imprudent, but on a regular twinned highway, I don't think of it as a problem at all.