This question is your opportunity to show the interviewer that you are wise and do not allow these unplanned situations to get the best of you.
Start off by telling the interviewer that you would assess how much time you have until your shift starts. Taking into account this amount of time, you would call/text a couple of friends or family members to see if they could get you to work on time. If they are unavailable, you would call for a cab, take city transportation, or walk depending on how far away you are.
Finally, be sure to mention that you would call the restaurant to let them know what happened if you will be arriving a few minutes late due to the setback.
"If my car broke down, I would immediately call the bar to let someone know the situation. I would then call a tow truck to take my car to the nearest mechanic. From there, I would take a cab to work. I rely on the money I make each shift so, rest assured, I would not skip out on a shift unless I were hospitalized!"
Entry Level answer example
"My father raised me to believe that if I am not ten minutes early for work, I am late. I would be very diligent to get to work on time, regardless of my car breaking down."
Experienced answer example
"This has happened to me before! When my car broke down, I called a coworker who lived across the street and asked them to fill in for me until I could get there. I ended up being only 1 hour late for my shift which was a relief."