Active Channel Management

Radio Communications you can Trust

The radio spectrum is filling up fast, meaning portable traffic signals have to communicate with each other in an increasingly congested environment.

Spectrum congestion is particularly prevalent in metropolitan areas where portable traffic signals, bank and utility telematics all share the same unlicensed radio channels. Construction sites are a particularly significant contributor to the problem since the use of high powered two-way radios was permitted in 2018. When communication between signals becomes difficult or fails, the impact to traffic and surrounding infrastructure can be severe.

Active Channel Management, or ACM, delivers reliable radio performance for portable and temporary traffic signals operating in challenging environments.

Why do you need Active Channel Management?

Traditional portable traffic signals operate using fixed channel radio communications between signals. The channel is selected by the operative at point of deployment, and manually entered into each signal in the set up.

The choice of channel is often left to guesswork by the operative, or through the use of scanning functionality in the signal controller.

If the selected channel were to become disrupted by congestion or a nearby interference, the lights would fail to red or lights-out. Without an in-built recovery mode, the signals would remain on red until an operative arrives to reset the system.

This can cause max disruption for road users and surrounding infrastructure, and creates a major headache for traffic managers.

Active Channel Management has been engineered to overcome comms failures through dynamic performance.

Herts TM

ACM has had a significant reduction on the number of call-outs received, and has eliminated nearly all complaints related to signal failures.

What does ACM provide?

Active Channel Hopping

ACM pro-actively and re-actively switches to the clearest radio channel to maintain strong connection at all times without impacting signal operation.


Enhanced Comms Data

Active Channel Management provides the user with detailed information about the performance of the radio link to each signal, helping identify and resolve any communications issues.

Active Channel Management Advanced Comms

Greater Resilience

Our ACM-enabled traffic signals are the most reliable in the market, able to confidently handle common system faults and auto-recover where necessary, helping minimise call-outs and avoiding painstaking system reboots. In the rare event that the system is irrecoverable, the signals will fail to lights out. This is deemed to be the safest outcome for motorists until the system is restored by the TM provider.

Fixed Radio Comms vs. Active Channel Management

Fixed Radio Comms
Active Channel Management
How is the best channel chosen? Largely decided by guesswork. Operatives do not have radio scanning equipment available and even if they did, they would be unlikely to be monitoring at the time that interference occurs due to its highly intermittent nature. ACM continuously measures all radio channels to identify which one is the most clear of interference over an extended period. It actively selects the most optimum channel to maintain reliable communication between signal units.
How is the decision to change channel made? The TM company either receives a complaint about the lights going out or being stuck on red. Often, a TM operative is deployed to site throughout the day to speed up this process. ACM will initiate an automated channel change whenever it identifies that another channel is clearer than the one it is operating on currently.
What does changing channel involve? The operative is required to turn off the lights then visit each signal in turn to enter a new radio channel. This can cause significant impact to traffic which is un-signalled during this period. When this occurs it is not uncommon for the operative to be subject to abuse and their safety is put at risk. Channel changes in ACM are fully automated. The lights change channel without going off. The entire process is seamless and road users are completely unaware the process has occurred.
Is that the end of it? Probably not. Sources of interference come and go. It is simply not possible to pick a single radio channel that will work in an urban environment for an extended length of time. The end result is that lights continually fail and require remedial action to get them started again. Yes, ACM constantly moves from channel to channel and the lights ‘just work’.

ACM delivers a significant boost in reliability for portable and temporary traffic signals

Discover ACM

ACM is available as standard on Metro, Evo 1 and our RadioConnect2 series portable traffic signals.

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rc2 metro and micro traffic lights

Frequently Asked Questions

Want to learn more about the importance of Active Channel Management? See our FAQ below!

The Radio Spectrum is the way of describing the limited real estate of frequencies described as the ‘Airwaves’. The Radio Spectrum is divided up into many bands and sub-bands which are regulated for use so that mobile phones, airport radar, TV, Radio, WiFi etc. can operate effectively.

The use of the Spectrum is managed in the UK by Ofcom in close collaboration with other countries so that continuity of services can be provided over as many jurisdictions as possible.

The continuous move to wireless services is putting pressure on the use of the Spectrum which requires increased Spectrum Management. Much of the spectrum is reserved for Military use and during the 2012 Olympics in London some of the Military spectrum was temporarily re-allocated over the fear of complete loss of some services from spectrum congestion which is as extreme as Spectrum Management can get.

Portable/Temporary Traffic Signals all use regulated ‘Licence-Free’ parts of the spectrum. Use of these designated parts of the spectrum means that operators do not need to pay for a radio licence to operate signals which condenses all operators into these specified sets of frequencies.

This leads to spectrum congestion in these allocated spectrum bands for traffic signals as well as other users in these bands such as walkie-talkies, instrumentation telemetry etc.

Spectrum sharing is a way to optimize the use of the airwaves, or wireless communications channels, by enabling multiple categories of users to safely share the same frequency bands.

Spectrum sharing is necessary because growing demand is crowding the spectrum, leading to inefficient services.

Portable/Temporary traffic signals operate in parts of the spectrum with other similar signals within approx. 1km range as well as other services. When deployed for periods in excess of a couple of hours the signals are at risk of being congested out of service by other new signals or services in the same part of the spectrum. This is in addition to existing services already present but not continuously on such as water reservoir telemetry.

ACM actively monitors the allocated spectrum when in service. It continuously searches out unused or better parts of the spectrum so that its service is better delivered. Additionally, it guards against the spontaneous introduction of new services which congest the operation by automatically moving to a better, less used channel.

This agile operation means the spectrum is more effectively shared for efficient use by all services.

  • On set-up, signals select their own best channel
  • Robust operation in ‘difficult’ environments
  • Signal strength reporting from the master controller for site management and diagnostics
  • Extremely low incidence Category 1 failure ‘lights out’ owing to clash of service
  • Rare nuisance service calls for interference from 3rd party services
  • A system running a particular channel at the end of the day could be running a different one the following day with no manual intervention as the system has found a better channel
  • Auto-recovery from congested comms system failure – reducing call outs
  • A step change increase in comms reliability

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