page_title: Dispatch (logistics)
section_title: Zone system to assign service calls
hierarchical_section_title: Dispatch (logistics) / Zone system to assign service calls
caption_attribution_description: Photo images from "Transit Management Centers: Human Factors Issues," TRB Human Factors Workshop, January 7, 2001, US Department of Transportation, Federal Transit Administration, Office of Mobility Innovation, Advanced Public Transportation Systems Division, Volpe National Transportation Systems Center. PowerPoint presentation by Don Sussman and Mary Stearns. Left image is dispatch with AVL. Right image is dispatch supervisor position. Drawing of channel appearance on console is self-made GDFL by David Jordan. Link to original PowerPoint file valid as of 04/10/2007.
context_page_description: Dispatch is a procedure for assigning employees or vehicles to customers. Industries that dispatch include taxicabs, couriers, emergency services, as well as home and commercial services such as maid services, plumbing, HVAC, pest control and electricians.
  With vehicle dispatching, clients are matched to vehicles according to the order in which clients called and the proximity of vehicles to each client's pick-up location. Telephone operators take calls from clients, then either enter the client's information into a computer or write it down and give it to a dispatcher. In some cases, calls may be assigned a priority by the call-taker. Priority calls may jump the queue of pending calls. In the first scenario, a central computer then communicates with the mobile data terminal located in each vehicle; in the second, the dispatcher communicates with the driver of each vehicle via two-way radio.
  With home or commercial service dispatching, customers usually schedule services in advance and the dispatching occurs the morning of the scheduled service. Depending on the type of service, workers are dispatched individually or in teams of two or more.
context_section_description: One method for organizing assignments in a manual dispatch system is to use a zone map system. Consider a community with four fire stations and two ambulance service providers. A grid is overlaid on a community map. Saint Proximal Medical Center ambulance is identified by the notation P while Distal Volunteer Rescue Squad is noted with a D.
  Each zone of the grid is identified with a progression of ambulance zones and fire stations. One zone might be labeled: DP241. This means fire station 2, then 4, then 1, then 3 would respond to a fire call occurring inside this zone. If fire stations 2, 4, and 1 were assigned to calls, Station 3 would be sent to this zone. Distal Volunteer Rescue Squad would be first-up for an ambulance call occurring inside zone DP241.
  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?
  Zone systems may include standby, move-up, or backfill points. For example, taxi drivers working in a certain zone in the evening hours may expect night club patrons to need a ride. Consider a standby point at Main Street and Railroad Avenue named N. Some fares will come from radio calls to dispatch. A taxi driver, Car 4, may go to predefined standby location N. In some dispatching systems, the driver will call the dispatcher and report they are available and located at standby point N. The dispatcher may respond by reporting the driver's position in the queue, "Car 4, second N." The first call in this district would go to the driver ahead of Car 4. Car 4 would be assigned the second call.
  If automatic vehicle location is available, it would display service vehicle locations on a map. The closest unit would be interpreted by the dispatcher looking at vehicle locations projected on the map.
caption: Dispatch consoles used by Denver RTD, a transit service provider in a US city. Drawing at right illustrates the controls associated with a single channel on the console. Photos courtesy of US Department of Transportation.
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