Sounds like a Queueing Theory problem (Score 1)

In my opinion you need to look at the number of servers and the time it takes to serve each customer. I doubt the company who runs this service will bring out more trucks to serve the community, but if you can increase the number of actual servers at each truck it may help. However, from what the article says I would think the issue is the time it takes for each customer to get their ice from the time they step up to the counter. With a bit more information you could definitely come up with the best solution, feasible or not.