Anne Posegate of the Washington Post’s Capital Weather Gang wrote an interesting article about the Urban Heat Island (UHI) effect causing cities to be hotter than surrounding areas:
Besides escaping to the countryside, most solutions boil down to one simple principle: Less concrete = less heat.
Adapting to hotter summers in the future involves reducing the existing Urban Heat Island (UHI) effect by increasing our vegetation and use of lighter-colored pavement.
Advantages of Gravel Roads
I have never heard gravel mentioned as a cool road surface, but light colored gravel should be considered a type of cool “pavement.” In addition to reducing the UHI effect, gravel is permeable surface that would help improve water tables by reducing storm runoff. Another possible advantage of pulverizing asphalt roads in cities is reduced traffic. Many people would avoid driving on gravel roads where possible.
The Return of Gravel Roads Part 1 contained some information about some counties reverting to gravel roads in order to save money.
Disadvantages of Gravel Roads
One disadvantage of gravel roads in big cities would be increased dust. The dusty gravel roads may create image problems for some cities. Additionally, lane markings would be challenging to maintain.