How are roads made?

Did you know the roads we drive on are built of multiple layers that are made up of different rocks?
There is often a grading created first to ensure the road can be built on stable grounds.
Then comes the sub-base where crushed rocks are laid, and after that comes a base layer which consists of smaller rocks usually asphalt at least where I live.
Then last but not least comes the paving (divided into lower course asphalt and upper course asphalt) and all of the road markings.
Often when engineers design roads they follow specific criteria from their province or city.
Also, highways, local roads, and internal lanes all have different thicknesses for each part of the structure.
This makes sense as some roads are used more than others.
At the city of Surrey, they used its own engineering design manual which comes from MMCD (Master Municipal Construction Document).
Of Course, the engineers would have more details on how the road is being built because they are simply more knowledgeable
but it would be pretty cool to design these roads in civil 3d. Also here is a picture of a little drawing that describes road structure.