Those aren't standard garbage trucks that go down the alleys; they're smaller than normal. I don't know that they're custom per se, but they are somewhat specialized. I've gotten many deliveries to my back entrance and you can't fit anything wider than a van down there.

Very little of the traffic on any surface street is commercial or emergency, but you still need the ability for them to get through. And it's not just about deliveries to businesses on that section of street - it's also about through traffic going from one side of the neighborhood to the other.