Is melting of Tar for road construction a reversible change?
Tar
 is mainly made up of a collection of very heavy hydrocarbons, with 
rather high melting temperatures. Commonly, it is mixed with some stones
 or gravel to make a harder surface for roads. It is possible to heat 
this up to soften or melt this; you can try it yourself by heating it in
 a metal can over a stove (don't use a container that you plan to keep 
clean) or in a wood or (char)coal fire.

EDIT: As MaxW pointed out, it would be a bad idea to do this inside the house because it would create a strong smell, similar to that created by whatever machine they used to make the road.