I've only once had to jump-start a car "on the road": when the car we'd driven from Denver to Boston "died" 2 miles from the end of the trip (alternator having given up the ghost sometime along the way and battery finally exhausted).
Every other event has been while the car was parked -- in my garage or at some "destination" -- just prior to setting out for somewhere (returning home, headed off to work, etc.).
If at home, you go find a friendly neighbor. If at work, find a workmate who's sympathetic. In a random parking lot, wait for a passerby and hope for the best.
Likewise, every time I have had to jump someone else's vehicle, it has been in a similar situation.