Why do they put a skim coat of asphalt on the road?

Question

It looks really bad and sometimes even bumpy to drive on. It looks like its is left over pavement or something.

Answer 1

Skim coating is used to extend the life of a street by up to five years.

There is little or no edge milling preformed and surface irregularities are repaired. The street is then swept and tack oil is applied. Utilizing the City’s paving machine, a one and a half-inch mat is laid down and a steel roller is used to finish the mat.

The skim coat should be placed down in warm weather and must be rolled immediately due to the thinness of the mat. The mat loses heat very quickly and the desired compaction can only be achieved while the asphalt is still hot.

Answer 2

It's sealer; or a "cold-patch" compound.

Sealer seals the pavement so water can't penetrate through.

Cold-patch is soft asphalt that is hammered in place to fill any large cracks.

Water will freeze and cause the road to crack in the winter (called "frost-heave").

Answer 3

its what they call "chip and tar".  the tar will be the adhesive to the asphalt and the rocks on the above layer however, the tar will seal the asphalt below to preserve the aging effect, and the rocks above will be in place to use for all traffic.you would need the rocks on the road because if you only use tha tar, combined with wet conditions would be like driving on black ice all the time, you would have control of the car go out the window.  although the road companies sometimes do use a very thin layer of properly mixed asphalt to go over the existing road, and this is for 2 things, 1: is to make the road aggressive so cars and trucks can run smoothly on it (less road noise and better traction control under wet conditions) and 2: to also preserve the asphalt underneath.  In my opinion, the newer ashpalt film is better than the chip and tar version, too noisy and the rocks come off after 1.5 years.  go figure.