It depends on what you mean by "highway"

Highway 1 in Chile



"Highway" 3 in Peru

So I learn something everyday as I research this route...

It turns out Chile has great roads. 

Peru, not so much.

Beware that, aside from a few major roads which are in good condition, most roads are unpaved and your speed on them will be severely restricted. For these roads a 4WD is necessary. This is especially true during the rainy season from November to April.