How long does tarmac take to cure?

Question:I had my driveway tarmac-ed today, and although the guys doing it seemed alright, they left (and aren't answering their phones) without letting me know how long I had to leave it before I could park my cars on it. Does anyone know? I really don't want to have tire-shaped indentations in it.

Answers:
Tarmac (short for tarmacadam, a portmanteau for tar-penetration macadam) Each layer is pressed with a roller to flatten it and to force the materials to bond together between layers. You can park/drive on it upon completion of installation.