What is the collective noun for ambulances?

There isn't a commonly accepted collective noun specifically for ambulances.

Here are some options you could use, depending on the context:

Formal:

* Fleet of ambulances

* Convoy of ambulances (implies movement)

Informal:

* Group of ambulances

* Squad of ambulances

* Lineup of ambulances

You could also use a more descriptive phrase like "a line of emergency vehicles" or "a fleet of life-saving vehicles."