I posted this recently:
http://ecomodder.com/forum/showthrea...ers-22015.html
I'd guess that the road bed can be improved in the way it supports bituminous paving? The major problem with concrete is that it is too stiff, and when the ground under it freezes, it heaves a LOT at the joints. Rapid heat expansion also stinks -- watch how the SUV *launches* into the air when it drives over buckled highway surface, starting at ~0:43 into this video: