The predefined order is created by persons with expertise in the service being provided, local geography, traffic, and patterns in calls for service. In assigning resources to a zone, decision-makers may consider that responding units must drive around freeways, lakes, or terrain obstructions in order to reach a zone. Zone boundaries and designations will periodically change as communities grow or lessons are learned during day-to-day operations. Consider a zone with an irrigation canal defining one boundary. If a car crashes into the canal, which zone is it in?