How Speed Cameras Work

How Speed Cameras Work 4 photos
Speed cameras have been around since the rise of the automobileSpeed cameras have been around since the rise of the automobileSpeed cameras have been around since the rise of the automobile
Speed cameras have historically been a sight dreaded by drivers even more than that of traffic policemen. They have not been around for all that long, yet speed cameras have quickly become one of the favorite pub, media and home topics for drivers and non-drivers alike. Are these things useful? Are they accurate in determining speeds? Should they be used? Do they interfere with those privacy rights everyone everywhere is now advocating?
For the purposes of this text, we couldn't care less what the answers to the above questions are. That's because what we'll try to do here is give you a better perspective on the technology, from a brief history to insights into the types of speed cameras and how they work.

Historically, the speed camera, or the traffic enforcement camera as police and administrative officers know it, came to be sometime in 1905. It's back then when a patent for a so called Time Recording Camera for Trapping Motorists was filed by an now unknown entity or individual. Notice the trapping term used in the thing's description...

The primitive design used the same working principle modern day cameras use, only that it took a more direct approach, as it was backed by the knowledge of how long of a distance was between two points on the road. The camera would take two photos of a car as it moved across the start and end points of a measured section of the road, and determined how fast the thing was traveling. It's not clear what exactly triggered the system, nor do we have details on whether it was actually used somewhere, to what effect, and for how long.

Since this early 20th century idea, work on traffic cameras kind of subsided for a few decades. Timid attempts were made in the six decades that followed, the most notable of which being that of a Dutch company called Gatsometer BV. The company was founded by Maurice Gatsonides, a rally driver who would not find fame in racing, but in the creation of a speed monitoring camera.

His idea started benign enough, as the man was trying to use the photographic equipment to monitor speed around corners in a bid to help him improve his driving times. The camera he ended up developing ultimately became the first automated road-rule enforcement system, and the Gatsometer company, now called Sensys Gatso Group, is one of the world's biggest suppliers of speed camera systems (oh, and you should also blame Gatsometer for inventing the first radar used in road traffic).

It was back in the 1960s when the first cameras started being introduced on a large scale. These film-based pieces of hardware remained in use until the early 1990s, when digital speed cameras came into the spotlight.

Currently, based on how they are used, speed cameras can be divided into three large groups: mobile systems, fixed speed cameras and average speed cameras. Based on the technology they use, they can also be divided into laser, truvelo and SPECS.

Speed cameras have been around since the rise of the automobile
Mobile cameras are the ones most commonly found on police vehicles, and in some places on this Earth they are also referred to as radars. Because of their nature, they come in a variety of shapes and sizes, and can be vehicle-mounted, hand-held, tripod-mounted and concealed.

Mobile cameras are equipped with built-in detection equipment, and that allows the carrier to accurately record the speed of incoming motorists regardless of whether they are stationary or not when detecting traffic. Another advantage for law enforcement is that they can also be used to detect speed regardless of the carrier moving with or against the flow of traffic.

The camera is based on laser technology, and it works by emitting a light beam towards the incoming vehicle. It generally takes the beam between 0.3 and 0.7 seconds to acquire and register a target at an operational range of 800 meters (2,624 feet).

What comes after the target is locked is called the Doppler effect, and that works as follows: the radar sends out the beam at specific frequencies and at an angle across the roadway. When a car enters its field, the beam is reflected and it changes frequency on account of the relative motion between the camera system and the target vehicle. The degree at which the frequency increases or decreases depends on the speed at which the passing vehicle is traveling.

Mobile cameras are also capable of detecting the direction in which the monitored vehicle is traveling to. Frequency is the main tool here as well: if it increases, the vehicle is incoming, while if it decreases, the vehicle is moving away from the carrier.

And now, a little on how the radar determines the size of the ticket you will get. Because the beams are directed at an angle (usually 20 degrees) compared to the road, the shift in frequency will indicate a speed lower than the target's actual speed. The radar calculates the slant angle and then, using calculations, it determines the speed in the direction of travel.


Speed cameras have been around since the rise of the automobile
Fixed cameras are all over the place nowadays. They most often come as strange, brightly colored boxes on the side of the road or dangling from various walls and poles. They can also be seen lurking on stoplights in most respectable cities in this world, or hanging on overpasses or bridges which intersect the road.

Most of the time, this type of camera is equipped with piezo electronic detectors to determine speed. They're nothing more than tiny wires embedded into the road surface - usually, there are two sets of wires per camera. The working principle is simple: when a car passes over one of the detectors, an electronic signal activates the camera, and it then determines how long it takes until the second wire is tripped, hence the speed of the vehicle. If the speed is higher than the limit on that portion of the road, a picture of the vehicle is taken.

Aside for taking photos, fixed speed cameras also record info on the date, time, location, direction of travel, speed, the speed limit on that portion of the road, and even the lane in which the car was traveling at the time of the "crime."

More advanced fixed cameras can differentiate between lanes and are even capable of singling out an offending car from a bulky line of vehicles. What that means is that trying to hide behind one of the vehicles in front will not work because of cameras' location above the road, and because they are mounted at an angle - any such camera will still be able to read the license plate. And the situation is even worse for speeding drivers when it comes to multi-lane roads where each of the lanes gets its own piezo detectors and cameras.


Speed cameras have been around since the rise of the automobile

The average speed camera, also known as automatic number plate recognition (ANPR) camera, is perhaps the simplest of all these tools. It does not rely on lasers, beams, GPS or any other modern invention for operation, but the good old photo camera and a little bit of math.

The working principle behind the average speed camera is pretty simple. Considering one knows the distance between two points, but also the time a vehicle departs one of these points, it's easy to determine the average speed of that car between the two points by measuring how long it takes it to travel the distance. If something is off with this math, such systems use infrared to look at the offending car and checks a vehicle database to identify the car's license plate.

Officially, this type of camera is called Speed Enforcement Camera System (SPECS), but is also known in some countries (like the UK) as Speed Violation Detection Deterrent (SSVD), and they work best when placed in sequence down a road.

It's pretty hard to say for sure which of the three systems dercribed above is best or worst. It depends on a variety of factors, including on which end of the camera you find yourself at one point. Generally, all three work as advertised, but if you are to ask us, the SPECS is probably the best.

First of all, it uses (and needs) far less pretentious technologies to work, making it less susceptible to the counter-measures invented over the years by offenders or those planning to offend (you know, radar detectors, jammers, and so on). Then, their findings are less susceptible to controversy and debate, the method used averages the speed of the car over a long distance, not at one fixed point as other systems do. That eliminates drivers' urge to slow down when approaching speed cameras for the simple reason such a maneuver would be useless.

After all, if the distance between point A and point B is X, and the time to get from A to B abiding by the law is Y, then how come you managed to do it in time Z, where Z is way smaller than Y?
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About the author: Daniel Patrascu
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Daniel loves writing (or so he claims), and he uses this skill to offer readers a "behind the scenes" look at the automotive industry. He also enjoys talking about space exploration and robots, because in his view the only way forward for humanity is away from this planet, in metal bodies.
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