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What Is the Difference Between a Speed Indication Device and a Speed Control Sign?

What is the difference between a speed indication device and a speed control sign?

LED signage is a valuable device in your arsenal of traffic control solutions, however, a question we often get asked is focused on speed control signs and speed indication devices (SID). What is the difference? When do you know when to use a speed indication device and when to use a speed control sign?

We have taken a look into what is a speed indication device and what is a speed control sign and explore when you would install each type of sign solution and how they can help.


Speed Indication Device (SID)

What is a speed indicator device?

A speed indication device or speed indicator display is a vehicle activated sign that uses radar to measure the speed of an oncoming vehicle and display this using LEDs on the device. A speed indication device is installed with the view to alert the driver of their speed and encourage the driver to slow down when the sign is activated. A speed indication device is inherently a vehicle activated sign as it uses radar technology to detect oncoming vehicles and measure their speed. A speed indication device can also be called a speed display sign as the signage is responsive to the speed at which a driver is travelling and displays this speed on the sign in real time.

The speed can be displayed on the device alongside a happy or sad face or a safety message of ‘Slow Down’ or ‘Thank you’. This can also include Welsh on the text display for the signage. Speed indication devices can use one-colour LEDs, red and green LEDs or multi-colour (orange as well as green and red), subject to whether the driver is conforming to the set speed limit or not.


When to use a speed indication device?

A speed indication device can be a useful tool to install in areas where speeding has been identified as a key concern. Speed indication signage can be used alongside existing mandatory speed limit signage to support the sign and draw driver’s attention to their speed.


Speed control sign

Speed signs that display the mandatory speed limit are speed control signs.

A speed control sign or speed warning sign is a mandatory sign that tells you what the speed is on that road ie 20, 30, 40mph etc. VAS Warning signs are used to alert drivers of a potential hazard ahead and so a speed warning sign advises the driver of a change in the legal speed limit. A hazard for other road users or pedestrians if not adhered to.

Speed control signs can be triggered by all vehicles or only those exceeding a pre-determined safe speed. They should be used to supplement fixed mandatory plate signing and not as a substitute for it. With a standard vehicle activated speed control sign, the speed does not change subject to the speed of a vehicle, it will always display the mandatory speed limit. The interactive sign uses radar detection to recognise oncoming vehicles and activate the LED signage.

It is possible for speed control signs to be flashing speed signs with corner amber LED clusters or feature red LEDs around the rim of the sign. Our compact speed control signs can alternate between messages, displaying a speed limit indicating “30” etc then a text display of SLOW DOWN. Each display will appear for a pre-set period. It is also possible to display a safety message below the speed limit on a speed control sign, and again has the option to add amber corner clusters for ultimate visibility.


When to use a speed control sign?

Speed control signs or speed warning signs should only be installed where there is an identified hazard or road safety problem, and not to solely meet a perceived need. Local authorities should work with local communities where specific issues and concerns are raised, to make sure the right solution is found. More information can be found here.


Clarifying some points:

Both types of signs are vehicle activated signage in that they can be set to only illuminate upon detection of an oncoming vehicle at set speed thresholds.

Both types of signs use radar technology so a radar speed sign could be either a SID or a speed control sign.

Both are capable of collecting and storing traffic and speed data.

Both signs can be classified as speed signs in that they both display speed on a road.

However, to differentiate these two types of signs: one shows the mandatory speed limit and one shows the speed of a vehicle in real time.

The experts at TWM are happy to discuss the best signage solution with you, assessing your specific requirements and developing a bespoke solution to meet your needs. Contact us to find out more.

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