SSM: Back to The Future.

Jack Stout defines System Status Management (SSM) as the art and science of matching the production capacity of an EMS system to the changing patterns of demands placed upon a system. SSM allows a system to manage resources appropriately, prepare for the best response to the next call, and allows a system to operate at its best possible ability. Other objectives are to improve productivity and ensure that proper ambulance coverage is available. To have a successful SSM system, a System Status Plan (SSP) must be created. To develop the SSP certain data must be collected. This includes how many patients are actually transported by the units.  The main idea of SSM is to provide the best response time and performance by the available resources. A SSP is also used to reduce costs, the use of on‑call crews and to improve productivity of an ambulance service.

The development of a SSP begins with gathering data. The data should be gathered over a five-month period (J. Wasko). This should allow sufficient data collection to measure a system. This data should consist of unit hour, unit hour ratio, peak demand and number of transports done by the ambulances. A unit hour is a fully staffed and equipped ambulance either assigned to an incident (run) or available for dispatch for one hour (Stout). The unit/unit hour ratio is determined by a mathematical calculation. It is a division of the number of transports during a certain period by the number of unit hours produced during the same time period (Stout). Here is an example of a unit/unit hour calculation. Steve’s Ambulance Unit 1 transported two patients in three hours Monday between 07:00 and 10:00 hours. The calculation would read 2/3, which would equal .666.  .666 would be your unit /unit hour ratio for Ambulance 1.

Some ambulance systems staff the same number of units and staff personnel twenty-four hours a day (Stout). There are systems today that still adhere to the same type of scheduling. Eventually it can cost the system more money to maintain this type of staffing. Determining the demand of system again deals with gathering data from the system. The finding of this data is to identify the high and low demand for ambulance service. Here is an example of what this type of data can conclude.  Ten ambulances are always scheduled to work on Thursdays during the day. After gathering the data (five months) it is determined that on average, there are fifteen calls (actual patient transports) during this time. The majority of the calls occur between seven and noon and occur at certain locations. This would allow the ambulance service to adjust their scheduling to meet the demands of the system. The solution to this is staffing and scheduling the correct number of units and staff to meet the service demands. The same principle applies when the system is at a decreased level of demand (Stout). The above situation is when a SSP would call for peak-load staffing. The ambulance service would know their potential demand for service Thursday, and would schedule the units and personnel to meet the demand.

An EMS Manager wants to have the best possible care giver on the street at all times.  They also want to be aware of the employee’s needs.  EMS personnel have different lifestyles and needs.  Scheduling units are easy, but staffing them with personnel might not be that easy.  SSM believes that twenty-four hours are not always the best for a SSP (Stout). The ability to be flexible in creating a schedule can be an important tool an EMS Manager must be able to administer. Scheduling is an important aspect to a SSP. When implementing a SSP, beware that changing a schedule could cause problems. The morale could be affected along with causing a conflict with the personnel’s family and life outside work. Shift bidding is one way to implement a schedule change. It may benefit an employee to work a certain schedule so they can go to school or spend more time with the family (Stout). Reducing a 24-hour unit to twelve hours could also achieve the same goal. Some ambulance organizations like the 36-hour first week, and thirty-two hours the second week, using a twelve-hour model (J. Wasko, personal communication). Employees might think they are receiving fewer hours when switching to a 12-hour shift.  In reality, they are still working the same hours a week. Another aspect that needs to be mentioned along with unit and personnel scheduling is post to post moves.

A post is a set location at which an EMS unit may position for some purposes of dispatch. Posts can be a street corner, fire station, hospital, or a location with access to main roads or highways.  A street corner post is the mostly widely used when first implementing the SSP. A post to post is moving units from one post to another so it can be in place and closer for the next dispatch (Stout, 1989). There are some negatives about posts and post to post moves. They include costs (in case the post becomes a permanent post), and employee well-being. The costs can include building and maintaining a facility for the crews. If corner posts are used, the ambulance should be well equipped and near a location where bathroom facilities are available. The ambulance should be made comfortable for the crews with a good stereo, mini refrigerator and comfortable seats (Stout, 1989). It may be good idea to ask the employee for his or her ideas about what kind of amenities would satisfy them. It would allow them to be part of the decision-making process.

The System Status Controller (SSC) is the one who is in charge of developing and refining the SSP. The SSC must be involved in all aspects of planning for the ambulance service.  SSM is a component of all aspects of an ambulance service. It has to strike a balance with four main components of the ambulance service. These are contract obligations, financial and vehicles (fleet maintenance), and employees (J. Wasko, personal communication). If the ambulance service has a performance base response contract they must meet, a SSP must be correct and updated on a regular basis. The contract may specify that the ambulance must be on location of an emergency within a specific time period.  If this contract is violated due to not arriving at locations within the time frame, the ambulance service could be in breach of contract and fined.  The fines could lead to financial problems within the organization. Financial consideration impacts on aspects of a SSP. Vehicles and their upkeep, salaries, and equipment, are some the financial considerations impacted.

The SCC needs vehicles on the street so the SSP can work properly. Without vehicles on the street, the ambulance service cannot honor the contract, and employees who occupy them cannot be productive. According to Wasko, SSM impacts also on the original components that were developed by the Department of Transport for EMS. Employees are needed to provide the service. The employees need the vehicles to provide the service. If the employees are in the vehicles providing service, which leads to generating the financial component.

Here is a look at a fictional EMS System that could benefit from SSM. The system averages 100,000 EMS calls per year. There are over 40 ambulances that serve the system and covers over 800 square miles. All of those ambulances are Advance Life Support (ALS) ambulances. When a call for help is established, both Communication Centers screens the 911 caller, uses EMD and priority dispatching. The closest ambulance is dispatched and is selected by GPS location. The system does a modified SSM or SSP. There are key areas that or  fire stations that are used when SSP is implemented. If an area is depleted of resources, an ambulance is moved from one area to the uncovered SSP. To improve this system the following areas would first need to be addressed.

Communication Center:  There are 2 Communication Centers that accept 911 calls. Only one center answers and dispatches EMS calls. The other center screens the call using EMD protocols and transfers the call and the EMD code to the other center for dispatch. Having one center performing all the functions would be best. The chance of an EMS call being missed or the communication between the centers when passing on a call could lead to other mistakes like a missing number an address or the street name. The benefits to implementing one center and a priority dispatch system allows sound decision making about EMS responses, safer responses, provide more information to the responding ambulances, and provide better service to the citizens (Clawson, Martin).

Peak Demand: The system provides peak demand coverage with different starting and ending times. There are certain times there might be a need for more ambulances to be on duty. During weekdays, the population in Wake County increases, at night the population decreases. The system will need to study their peak demand for calls and staff the system with the proper coverage. This could mean maybe adding a 2-level service. Continuing to gather this type of data allows the proper staffing of ambulances and personnel. It may also reveal that additional ambulances are needed during the day and less at night. Is it fair that one ambulance is always working and while others are idle?

Scheduling: Once the above data is analyzed, it can directly affect the schedule. If it is discovered that thirty ambulances are needed during a Friday night, a schedule can be created to meet the demand. Starting and ending times could be arranged to meet the needs of the service, management and personnel. By offering a flexible schedule it may improve personnel morale, family life, and allow personnel to go to school

Deployment: Again, after gathering the data and determining peak demand, and where the next call could be, a post could be created. The idea is to provide the best service, productivity of personnel, and respond to an emergency using the correct resources.

The above is just an initial approach an EMS could use SSM to improve the service it provides. It may help reduce costs, employee strain and provide better service for the citizens.

SSM is an important tool for an EMS Manager to learn. It may allow the EMS Manager(s) to create a plan to improve the service it provides. It can also be able to identify problems within the service, help reduce costs and improve productivity of the organization.



Clawson, J. J. & Martin, RL (1990). Modern Priority Dispatch. Emergency, January, 1990.   In J. J. Clawson, MD, S. A. Hauret, & R. L. Martin (Eds.) . Advance EMD Course Manual  (pp I-7-12). Salt Lake City, UT.

Stout, J. (1989).  Advance Methods in System Status Management. The Fourth Party, Inc.: USA.

Stout, J. (1989). System Status Management: The Fact it is Everywhere. Journal Of Emergency Medical Services, April, pp. 65-71.

Stout, J. (1989). Peak-Load Staffing. Journal Of Emergency Medical Services, August,  pp. 73-6.

Stout, J. (1984). How Much is Too Much. Journal Of Emergency Medical Services, February,  pp. 26-34.

Stout, J. (1984). Priority Dispatching Vs. Call Screening. Journal Of Emergency Medical Services,

May,  pp. 34-8.

Stout, J. (1983). System Status Management: The Strategy of Ambulance Placement. Journal Of Emergency Medical Services, May, pp. 22-32.

Washko , J (personnel  communication)



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