Traffic light pre-emption

States of Jersey
Orion Radio Modem
Traffic light system control
Industry / Vertical:
Emergency Services/Transport


The largest of the Channel Island, Jersey is self-governed by a parliamentary democracy known as States of Jersey. This assembly, which operates under a British constitutional monarch, oversees and runs its own financial, legal and judicial systems. The government consists of a Council of Ministers that organise and prepare policies and legislation.


Traffic signal pre-emption allows control of a traffic light system from a vehicle or a central hub. Mainly implemented in city and urban areas, this system is designed to assist emergency vehicles by remotely overriding traffic signals, stopping the flow of opposing traffic to create a clear path.

There are a variety of traffic signal pre-emption systems available with different levels of reliability. Emergency vehicles can be fitted with an infrared sensor that emits a line-of-sight signal to a sensor on each traffic light as it approaches. However communication can be affected by unexpected vehicle obstruction and adverse weather conditions.

Similarly, a pre-emption device installed on each traffic light can detect different acoustic properties in the vehicle’s warning siren when attending an emergency call. Unfortunately sound waves reflecting off buildings in some metropolitan areas can distort the pattern and in some cases fail to override the traffic signal.

Another option involves a Global Position System (GPS) based system that transmits the location of an emergency vehicle to central hub for the controller to gauge when to reverse the lights. However the loss of a GPS signal when travelling through an ‘urban canyon’ is a common occurrence. Finally a radio signal can offer both long and short distance transmissions from a central control room to the traffic lights.

Despite its small size, Jersey has 350 miles of roads and one of the highest ratios of cars to people in the world, with capital St. Helier prone to dense traffic, especially at peak times and during the summer tourist months. To help assist emergency service vehicles travelling through the town, States of Jersey looked to install a traffic pre-emption system.

States of Jersey decided to implement a radio based system, remotely controlled by the 999 emergency call centre on the Island. The Island’s government turned to UK-based wireless specialists, Wood & Douglas to provide the technology.


The complex nature of the town’s traffic light set up meant a streamlined wireless communications systems was required. With this in mind, Wood & Douglas recommended the Orion Radio Modem. Up to 255 units can feed off the same frequency making the system straightforward to control remotely from a central source. The Orion Radio Modem delivers fast transmission speeds and a reliable performance that can ensure the lights are changed quickly and effectively, enabling emergency services to travel to destinations unimpeded.

With a robust wireless network in place, the emergency call centre was able to reliably and easily control St. Helier’s traffic signal in moments of crisis, radically improving the response times of emergency vehicles while preventing accidents and increasing road safety.

  • Critical transmission signal from emergency call centre to traffic lights
  • Radio modem module delivers reliable wireless link with up to 255 units able to work on the same frequency

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