Nice to hear you made it out! Possibly worst cause scenario = you crash & wreck & mauled & posting this from hospital bed.
Anyhow, this got me thinking considering I've never had this problem or thought about it.
Considering, I've seen mail carriers with small white and red bottles of pepper spray attached to the strap of their bags, mace would be a good thing to have in a jersey back pocket.
For a more humane way, a mini propelled air horn should theoretically shoo such a dog away.