A question

I have a question for anyone who knows something about paved roads and their maintenance. My daughter, the civil engineer draws a blank on this.

So far as I know, south central Wisconsin is unique in "maintaining" the asphalt paved county and township roads around here by spreading a nice thck coat of tar or oil, then a nice thick coating of fine pea gravel. The oil gets on anyone's vehicle who is unlucky enough to have to use the road, and the pea gravel is a special treat to two-wheeled traffic. My daughter came out today on her bike and had to negotiate some curves on a county road so treated - luckily she knows how to ride.

Is there actually any benefit to this technique, aside from making some politically connected people's brother-in-laws rich? It certainly ought to make the greenies happy, spreading all that oil to leach into the ground...