Hot lances are used to heat the asphalt for a variety of reasons. Asphalt is a dense fluid and with heavy loads can be moved aside, called kneading (like bread). This can be commonly observed at bus stops. Heating the asphalt permits it to be re-rolled to a flatter shape, removing ripples, without milling and replacing the surface, and may also remove cracking, but it would depend on the age of the asphalt.
Another reason is to soften the asphalt to place a pattern that is filled with a colored plastic to create patterns at crosswalks.
The only “fire machine” used around roads is generally a cookpot to melt down blocks of tar, to spray around the holes prior to filling with asphalt.
