Guess: less road and less bitumen road in hot areas; elevated roads on coastal and flood areas; concrete road in the permafrost, etc.
b.) What are the direct and indirect factors of the influence?
GDP effects (lower, less infrastructure needed), agriculture transportation need changing, hurricanes and other weather extremities, etc.
c.) Empirical research or deduction? Evidenced past or expected future?
Maybe you want to find case studies (e.g. outer banks in NC or the Keys in Florida road reconstruction) or use see level forecast maps in coastal areas.
If you have time, please share more information about your forming idea.