Evaluating Vehicle Pre-Emption Systems

I have been writing for Firehouse® Magazine for a number of years. In that time, I have forged a lot of friendships and attained close bonds with many fire departments. Among them is the Bowling Green, KY, Fire Department.

About two years ago, Bowling Green Captain Keith Mefford was given the task of evaluating emergency vehicle pre-emption systems for the department. Contained in this column are the results of his work.

Fire departments have been pre-empting traffic signals for more than 20 years. No one can argue that a green light in the favor of an emergency vehicle provides for a safer and quicker response. An emergency pre-emption system lets a fire vehicle emit a coded message to an intersection, informing the signal controller to provide a green light before the truck enters the intersection. The system not only provides for a green light, but activates up to 1,200 feet away to allow forward traffic to clear before the emergency vehicle arrives at the intersection.

Until recently, the pre-emption market was dominated by one system; however, growing market demand and improved technology have drawn competition into the field. The introduction of new companies into the market has made selecting the proper system for your jurisdiction a more difficult task.

There are several systems available today (see table on page 34) offering a variety of technologies. The systems can be categorized into three basic types:

  • Sound-based system. Listens for a pre-programmed sound, such as a siren, and sends input to the traffic controller.
  • Optical system. Receives a pre-approved optical pattern, such as strobe light, and provides input to the traffic controller.
  • Global positioning/radio system. Monitors a vehicle's position with the Global Positioning System (GPS) and initiates a radio signal to the next intersection.

Each system should be investigated and tested prior to selecting the type to best suit your department's needs. The following information provides an overview of the process used by the Bowling Green Fire Department during its recent evaluation of the pre-emption systems currently on the market.

Will You Benefit?

First, determine whether pre-emption is right for your department. Several published reports have supported pre-emption in regard to improved response times, reduction in accidents and wear on equipment; however, several other factors must be considered before entering the pre-emption vendor evaluation process:

  • Will traffic agencies (local and/or state) approve pre-emption signals?
  • Is the funding available?
  • Will the system be used by multiple agencies?
  • Will the system be used on low priority for mass transit?
  • What impact will pre-emption have on normal traffic flow?
  • Will the municipality or an outside contractor install and maintain the system?

The evaluation process should not begin until the local fire, traffic, highway, finance and other related departments can agree on the above issues.

Vendor Evaluation

Once a decision has been made to install a pre-emption system, a thorough evaluation should be performed. Several companies have entered the pre-emption market in recent years; therefore, an investigation should be conducted to ensure that all potential suppliers are identified. Sources for such information include traffic engineering journals, the Institute of Transportation Engineers (ITE), fire service trade shows, the National Fire Academy Research Center and other fire departments.

A questionnaire should be mailed to each potential supplier. The questionnaire can be used to narrow the list of vendors for your department's evaluation. Each vendor should be contacted by telephone prior to mailing the questionnaire for notification, as well as to ensure that the address and name of the contact person are accurate.

The following topics should be addressed in the questionnaire:

  • Explaining the function of the system.
  • The number of years on the market.
  • Reference list/users list.
  • System compatibility with local traffic controllers.
  • Warranty terms.
  • Service and training.
  • Programming and downloading features.
  • Financial/company history (a Dun & Bradstreet report).
  • Willingness to install field demonstration and trail period.

A follow-up call should be made to any company not responding to the questionnaire by the deadline to ensure it receives a copy. All questionnaires should be reviewed by the appropriate agencies to determine which systems will be included in the evaluation.

Field Demonstration

Installation. Each pre-emption company being evaluated should be asked to install its system on one signal and two trucks for a minimum of one week. All companies we contacted were eager to demonstrate their products (although scheduling the multiple agencies needed to be set up a signal was sometimes challenging).

The traffic light chosen for the field demonstration should be indicative of the intersections where the pre-emption system will be installed. The intersection should have four directions of traffic, with turn-lane signals and a pedestrian crossing, if possible.

Be sure to specify factory-made equipment with the exact features you need, not equipment built in a laboratory and fine-tuned for demonstration purposes. The pre-emption company will provide the equipment necessary; however, the agency coordinating the instillation must provide a bucket truck and crew, along with a traffic engineer to assist with the installation. Notes should be taken to reflect the organization and technical knowledge of the pre-emption representatives assisting with the installation.

System performance. A test with established parameters should be performed on each system. Testing should be preformed under a variety of approaches, including:

  1. A single apparatus approaches the intersection.
  2. Two apparatus approach from the same direction with no delay between trucks.
  3. Two apparatus approach from the same direction with a 30- to 45-second delay between the two trucks.
  4. Two pieces of apparatus approach the intersection from opposite directions at approximately the same time.
  5. Two pieces of apparatus approach at a 90-degree angle and enter the intersection at approximately the same time.
  6. One apparatus approaches the intersection while the signal is in the pedestrian mode.

The system should remain on the signal for a minimum of one week. Testing should be conducted at different times of the day and night, under varied traffic conditions (some systems may be adversely affected by wind or rain.)

A form should be provided to crews during testing for recording each system's performance on actual runs during the demonstration phase. Information to be gathered during the testing includes the number of successful activations, sufficient lead time, whether a signal held for a specific duration, whether pre-emption was dropped after apparatus left the intersection and false activations in the wrong direction.

It is important to ensure that all participants recording results are familiar with the expectations and that those results are recorded accurately. A company representative should be allowed to review these results and investigate any discrepancies.

Reference Sources

Each company should be given a reference list (users list) to reply to the questionnaire. The company you are evaluating should supply a list of all departments using its system (as opposed to a hand-picked list); make random selections from this list to ensure a wide range of sources. When talking to references, ask about other departments using pre-emption and add those to your reference list. Also, confirm the model and series of the system being used.

Call all references, if possible. We received negative comments from departments that were on the vendor's original reference list. Reference information should be obtained from both fire and traffic department personnel (we occasionally received conflicting comments) and everything should be documented. Review and categorize reference information to provide a fair overview of the data gathered.

The concerned agency representatives are to determine the type of operating system best suited for your jurisdiction. These representatives should evaluate the field demonstration, reference information and questionnaire responses.

The specification should include technical information for the system selected, ensure compatibility with all types of signal controllers being considered, detail apparatus requirements, and list service, warranty and training requirements. The specification should state that the pre-emption company is responsible for final adjustments at each intersection following the installation.

If the system is being installed by an outside contractor, a separate specification must be developed listing the specific intersections, number of directions, type of mounting (span wire or mast arms) and any other remote detector locations. The number of days to be allowed for the instillation should also be specified.

Bid-evaluation criteria should be developed and documents after the specifications are complete. Any traffic problems or system maintenance will probably be the responsibility of the traffic department, therefore, it should be given ample opportunity to provide input during the bid performance, during field demonstrations, company history/reference information and cost.


Performance of pre-emption systems has been improved greatly in recent years with several companies offering highly reliable, multiple-function systems. The influx of new companies and advanced technologies has given emergency response agencies a greater flexibility when choosing a system but is has also made the decision making process more demanding. A detailed analysis will ensure that your jurisdiction selects a system that provides years of dependable service.

I would like to thank Captain Keith Mefford for his contribution to this Emergency Vehicle Operations column. Also, my thanks go out to the Bowling Green Fire Department and Chief of Department Gerry Brown.

Michael Wilbur, a Firehouse® contributing editor, is an FDNY lieutenant in Ladder Company 27 in the Bronx and a firefighter in the Howells, NY, Fire Department. He is an adjunct instructor at the New York State Academy of Fire Science and the Orange County Fire Training Center. Wilbur has developed and presented emergency vehicle operator courses throughout the country and has consulted on a variety of fire apparatus issues.