The most important reason for the accidents that priority vehicles involved is the violation of red light. For this reason, in many countries, especially in European countries, “priority vehicle passing systems” are applied at signalized intersections. The priority vehicle passing system (Emergency Vehicle Preemption) is based on the principle of automatically detecting the approach direction of the vehicles with the priority of crossing at signalized intersections and ensuring that green light is illuminated in the relevant direction. Therefore, vehicles with priority passing leave the intersections fast and safely because of these systems. Some cities where these systems are applied and the rate of shortening average travel times in these examples are as follows:

  • Vicenza, Italy – %23,8
  • Leeds, UK – %10
  • Stuttgart, Germany – %50
  • Toulouse, France – %11
  • Toronto, Canada – %15
  • Sapporo, Japan – %20,8


Vehicles with the priority of passing are listed below respectively:

  1. Ambulances, vehicles carrying wounded or emergency patients,
    2. Fire trucks,
    3. Municipal police vehicles follow convict or defendant
    4. Vehicles belonging to officers who have followed a vehicle with a traffic offense or who are driving to an incident or accident in order to protect traffic safety or to confiscate a traffic accident,
    5. Vehicles belonging to disaster and emergency services in case of a disaster and emergency situations,
    6. Vehicles used for protection and protected vehicles.

The rules should be obeyed by vehicles with priority passing are as follows:

  1. These vehicles have the right to pass while on duty.
    2. This right should not endanger the people’s life and property safety. These vehicles should warn others by auditory danger signals and visual signs.
    3. These vehicles are not subject to traffic restrictions and prohibitions in accordance with applicable laws and regulations.
    4. If two or more vehicles with priority of passing encounter each other, priority of passing will be according to the order above.
    5. It is forbidden to use the right of priority passing when it is not mandatory.

Emergency vehicle preemption system is offered with different bases such as acoustic sensor based, radio receiver-transmitter based, infrared based, GPS receiver-transmitter based. GPS based emergency vehicle preemption systems are preferred more because of the advantages it provides in terms of cost, ease of application and performance.

GPS based emergency vehicle preemption systems consist of:

  1. A GPS unit that determines the location of vehicle and transmits it to the center,
    2. A central software that calculates intersection distance according to the coordinates from the vehicle,
    3. Integration unit that transmits green light command to intersection controller.

GPS transmitters are already available on ambulances and fire trucks. Therefore, there is no need for any installation for these vehicles.

The working principle of GPS based emergency vehicle preemption systems are as follows:

  1. Location information of the vehicles with priority of passing is transferred to central software continuously and instantly by GPS transmitters.
    2. Central software continuously calculates the distance of related vehicle to the signalized intersection.
    3. If the vehicle approaches more than 200 meters (or determined distance) to an intersection on its route, the ‘Green Light Command’ is transferred to the relevant intersection controller device for the direction in which the vehicle enters the intersection.
    4. The intersection controller device that receives ‘Green Light Command’ illuminates the green light in the direction of vehicle by applying necessary protection times (2-3 seconds)

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