The following is a preview of a book coming soon from Bradshaw Consulting Services to be titled "Closest Vehicle Dispatch: A Primer for Fire" which is a follow-up to "Dynamic Deployment: A Primer for EMS". Watch for the new release in time for the FDIC 2017 conference at the end of April.
The modern legal definition of response zones can be found in the Code of Federal Regulations, which states that the “first-due response area is a geographical area in proximity to a fire or rescue facility and normally served by the personnel and apparatus from that facility in the event of a fire or other emergency.? (44 CFR 152.2) This banal definition glosses over some very interesting history in the development of modern professional fire departments. In the mid-nineteenth century, there were frequent, and often bitter, disagreements over territories that sometimes resulted in physical confrontations. In fact, the politically powerful New York City volunteer fire companies of that era were known to send out runners ahead of the engine in order to claim the right to fight a particular fire and thereby receive the insurance money that would be paid to the company who fought it. While the monetary incentives are not nearly so direct today, there is still a great deal of pride invested in being the “first responders” to an incident. It would not be a difficult argument to make that we haven’t changed as much as we would like to think in regards to response.
A retired fire chief recently relayed a story to me about an engine crew that raced through a residential neighborhood in order to beat another engine that had been dispatched for mutual aid since the “first due? engine was out of quarters returning from another call. The need was so great to be the first responding company in “their own area? that they willingly disregarded the safety of the public that they had sworn to serve simply to avoid the embarrassment of being second to a call that was “rightfully theirs.?
The concept of the “first due” area is a strategy to automate a century-old manual concept of pre-assigning the closest resources to specific structure addresses within a fixed response area. The thought that a central station will have the closest apparatus to any potential fire in their district is simple, but with the increasing complexity of urban transportation networks, it is also an increasingly simplistic idea. The reality is that traffic patterns, and increasing traffic congestion, can dramatically change response times, particularly in high density population areas.
Public safety vehicles, even those running emergency traffic, can sometimes struggle to reach the posted speed limits at certain times during a shift. Alternatively, a lack of traffic at other times will permit the discretion of rates above the normal traffic speed. These periods of diverse congestion levels exist not only for intermittent periods of time but can vary dramatically by the direction of travel as well. Additionally, these temporal and directional impacts are confounded by the fact that station locations are often inherited positions that were designated many years earlier when housing, demographic and development patterns were very different from today. In most areas, fire station placements have grown through ‘incrementalism’, often tainted with political influence. In some jurisdictions this inheritance may go back over a century or more. Not all current station locations are the result of some forward-thinking intelligent design. The result of fixing address assignments to these past growth patterns may, or may not, represent who will be able to arrive first on the scene with the right resources. Furthermore, the common overlap of nearly a third between each of multiple urban engine companies means that when they are each dispatched from quarters, the next few arriving fire units, under normal conditions, will likely have a similar response time to that of the “first due? apparatus.
The “effective service area? of any station will vary during different times of the day based on traffic congestion. On a typical morning, as most traffic is heading toward a downtown business district, an urban station located at the city center will be able to travel outward toward the suburbs with relative ease. At the end of a normal business day, that same station will find that it can no longer travel as far in the same direction in the same length of time. Any sort of break in the normal business routine will further alter that pattern. These exceptions can include weekends, holidays, or special events. Most areas will also experience seasonal changes to traffic as a result of adding school buses or tourists to the roadways. The result of traffic is the evolution a unique “first due? area for different hours of the day and days of the week during different months of the year. A “fixed?, or “average?, first due area must either ignore, or at the very least, generalize the pressures of these growing realities.
Generalizations of Effective Service Areas as Impacted by Primary Traffic Patterns
Morning Afternoon
During a typical morning “rush hour? period, the heaviest traffic may be to the north and west as in the left example making response in that direction relatively more difficult than moving to the south and east. Consequently, the effective response zone represented in gray around two example stations will compress moving with the traffic and elongate against that traffic. In the afternoon, this pattern will reverse since the heaviest traffic would now be moving away from the downtown area making response to the south and east slower as compared to the morning pattern and therefore reforming the effective service area in the opposite direction.
The dispatch of a theoretical “persistently closest resource? is made even more difficult when we consider that an increase in call volume makes it increasingly common for an apparatus to be dispatched when it is already out of its assigned station, either on or returning from another alarm. With an increase in call volume, the chances of another call leading to a dispatch before a unit has returned to its station are only increasing. These moving vehicles will have a significantly different effective service area and a different proximity to an incoming alarm when compared to an apparatus that is currently parked in a given “first due? station. Additionally, the “chute time? in preparing the crew to respond is completely eliminated when the dispatched vehicle is already moving. In this case, the effective response area is larger when considering response time than an apparatus that is parked at its station. However, this dynamic nature of the responding vehicles can also work against the efficiency of a traditional “first due? response. Consider that an apparatus may be available after clearing an alarm at some extreme point within its district when a call is received from an opposite extreme location. The mere fact that the responding vehicle is moving may still not overcome the greater distance that places it significantly further from that next alarm than an apparatus that is parked elsewhere. In this case, the closest unit may well be one outside of the assigned primary response area.
Impact of Increasing Call Volume on Effective Service Areas
When an apparatus clears a call, it becomes available in a different location than the station and although it is capable of responding with a “zero chute time”, its distance from the station will impact its effective service area possibly putting it further away from the “next call” than a neighboring station “in quarters”. As call volume increases, the likelihood of being dispatched while returning from another call only increases.
These changing logistical dynamics significantly alter the performance realities for modern fire stations from simple planned service delivery to a complex system of matching dynamic resources to increasing demand. Meeting the expectations of your community requires more than the historical paradigm of “first due? scenarios assisted by mutual aid to that of a cooperative system approach designating primary and secondary response functions on-demand and independent of an arbitrary enforcement of outdated patterns of convenience. Fire departments must literally become dynamic fire services requiring an intelligent coordination of these mobile resources.
High Performance EMS 