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Go slow: how do speed cameras work?

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September 8th 2022 info

Speed cameras. We’ve all seen them, intimidatingly towering over our roads, looking all smug. It’s fair to say that, for most drivers, the sight of a speed camera is certainly an unwelcome one.

To much disproval, these large yellow boxes were introduced in the late 60s as a speeding deterrent. Earlier models were much less complicated than the ones we have today, which begs the question: how do speed cameras even work? If you’ve ever driven past one during maintenance or installation, you’ll have been introduced to the rather intricate makeup of these devices.

Expand your speed camera knowledge as we explain how they work and why we need them.

How do speed cameras work?

Speed cameras work by recording a vehicle and its number plate when it breaches a given speed limit. Not all speed cameras use images to capture their data, with some models using Automatic Number plate Recognition (ANPR) to record information.

Based on programmed speed limits, speed cameras are able to detect how fast a vehicle is going by measuring the distance covered in an amount of time. If this duration is quicker than expected, the driver’s information is recorded along with proof.

What types of speed cameras are there?

In the UK, there are five main types of speed cameras used to put motorists off speeding:

Average speed cameras

Rather than capturing the current speed of a vehicle, average speed cameras aim to capture an aggregate speed that a vehicle is travelling. These cameras are more effective for longer stretches of road, as they can determine if speeding is for a temporary amount of time, or over a prolonged journey.

Average speed cameras come in sets, reducing the risk of a single point of failure that is typically observed with regular speed cameras. These sets are then placed in regular intervals.

Fixed yellow-box speed cameras

Yellow-box speed cameras are by far the most common types on UK roads. Characterised by their iconic, striking yellow colour and boxy form factor, these speed cameras can be found almost everywhere. They operate via a single camera that monitors the speed at which vehicles pass by. If one is found to be exceeding speed limits, the camera takes a quick photo of the vehicle, including its numberplate.

Variable speed cameras

Variable speed cameras work very much like traditional, always-on cameras, except they are only functional for a specified amount of time. This allows for speeding motorists to be caught off-guard, without much warning as to when a camera is active.

Traffic light cameras

Traffic light cameras are similar to speed cameras, except they monitor for traffic light associated infringements like passing red lights or keeping tabs on pedestrian activity.

Mobile speed cameras

The final type of UK speed camera is one that’s operated manually by traffic enforcement officers. After parking up in designated areas on dual carriageways, bypasses and more, these cameras serve a similar purpose to yellow-box cameras.

The main advantage of these cameras is that they can be moved around at will, surprising unexpecting motorists and catching them off guard.

Due to their mobile nature, you might be wondering: do mobile speed cameras work in both directions? The answer is a simple no. As these cameras are designed to be placed in an area and then moved around, they typically only work in one direction.

Why do we need speed cameras?

By far the greatest question that most motorists have around speed cameras is why we even need them to begin with. The simple fact is that we need speed cameras because speeding is dangerous.

Acknowledging this risk, motoring standards agencies across the world sought for change in the form of evidence-based speed cameras to name and shame offenders. Nowadays, speed cameras are seen as more of a deterrent to prevent speeding, with plenty of warning given to drivers before they enter a speed camera zone.

How to tell if a speed camera is working

Generally, you’ll know if a speed camera is working if its vision is unencumbered by maintenance signs. Aside from this, there aren’t really many indications of operating status.

Apps like Google Maps will allow users to place warning signs on top of directions for other road users to see. If these are listed on your journey, it’s likely that someone has been caught by the camera, verifying the fact that it is operational.

Do speed cameras flash?

Contrary to popular belief, not all speed cameras flash upon speed detection. Some older models do, but these are usually replaced quite quickly with more efficient futuristic cameras that obscure flashes via filters.

After all, camera flashes are major distractions while driving, so minimising the amount of flashing that speed cameras do is a major focus for road safety.  

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