Anybody use hot tar to fill driveway cracks?

[cmac2012]

One of my best clients wants me to fill a buncha cracks in her driveway with hot tar. Her place is on a bit of a hill and the soil/substrate probably wasn't prepared properly for the driveway. Her feeling is that water migration is slowly undermining it, making the cracking worse. She might me right. Re-doing it with proper preparation is of course the way to go but she wants to wait for more funds as she has other stuff that's more pressing.

The kind of equipment needed for this is not likely to be easily available at rental yards, methinks.