service division
Supply and response areas of a utility or emergency service, cut by network and driving time.
A service division is a division whose areas state who supplies or responds at a given address: an electricity, water or waste operator, an ambulance or fire service, a hospital catchment. The operator or the authority commissioning it sets the boundaries.
The network or the response time governs the cut, so the boundary follows pipes, cables and driving distance rather than settlement edges, and it is redrawn when the network or the depot changes. Each service divides the ground on its own terms, so the areas of different services rarely coincide.
An administrative division is the municipality's own subdivision of itself. A service area exists to route a supply or a response, and it regularly crosses municipal boundaries to do it.