When they put down blacktop, they do not prepare the bed properly. Then they put down a skim coat of asphalt which gets beaten up by the traffic in a few months so it looks good when the President drives over it. Poor execution and shoddy workmanship are the reasons. They need to redo the road properly and not just keep putting quick and poor repairs on top of a bad and irregular surface.
Exactly right - an asphalt road is a flexible structure but it requires a strong but well graded and slightly-giving base, usually compacted crushed rock which has some draining capability, preferably.
Paving over mud, which they do when patching in the DR, creates a base that flexes too much and it is only a matter of a few heavy truck axles until the asphalt shears and more water enters to separate the asphalt from any binder between the upper and lower strata.
Concrete plugs don't flex with the asphalt so it is like mixing oil and water - they separate.
A solution while keeping a road open is hard because the road should be taken back to dirt, reshaped for drainage, culverts added and a real road bed places that will support the loads (Think flagmen, one lane and lots of traffic backup - except for the taxis who would drive around the flagmen).
One other note is that many of the dump trucks hauling dirt are way over loaded - if you see mounds above the side boards on a 10-wheeler it is over loaded and no asphalt road can stand up to that for long, nor truck springs.
But what annoys me just as much is adding layers to streets without grinding down the wearing layer so that the asphalt is almost level with the curb except for a small deep strip along the curb where putrid water collects.
