I’m sure most people have noticed this. Why is that when driving a car at high speeds on a concrete road, it creates that rather high-pitched whirring sound, compared to the relative silence of driving on an asphalt road? Does it have something to do with the way the rubber tires at high speed interact on the concrete versus asphalt? Thanks. 
Concrete is harder than asphalt pavement, and thus tends to reflect more tire noise than the softer asphalt, which absorbs more tire noise.
My hypothesis, anyhow.
My guess: grooving or other surface roughness deliberately put into the concrete. Oterwise, especially when it’s wet, concrete tends to be pretty slick.
Where would these highways be, roughly? Might give us more of a hint.
Concrete road beds have regularly spaced grooves in them (to provide traction) that run perpendicular to your tires, so when you drive over this surface at a high rate of speed you hear the higher-pitched whirring sound. The rate at which these grooves pass beneath your tires determines the frequency of the pitch. Asphalt surfaces, on the other hand, are irregular and produce more of a “white noise”. This is based purely on my observations as I am no highway engineer nor a construction worker.