Composite Roadbeds

[roadman65]

https://www.flickr.com/photos/54480415@N08/53358705250
Just curious to know when the applications of the different asphalts are warranted.

I've researched the composite type and they seem to be used for overlaying concrete bases, but Kansas likes to use them on rural roads with low traffic counts like the one in the above link.

The main highways seem to used a heavier base with more petroleum in it due to abuse from vehicles, but lately recycled asphalt has been being used to cut costs.  Plus the availability of it.

FDOT uses a white stone base, but when they do use black asphalt after months of abuse  does seem to create a loud roar on your tires. I'm assuming the heat and also the white stones are most available in Florida.

So big question is what are the different applications used for each type? Plus why do states vary on applying them?

[Bitmapped]

Most states have different mixes they use based on the expected volume of traffic and how much of that is truck based. WVDOH, for examples, uses Superpave-based mixes on Interstates and Appalachian corridors. Other roads get Marshall Medium or Marshall Heavy mix asphalt depending on the calculated wheel loadings for the road.