Traffic Cameras, How They Work, Types and Where They Are

Radars are the most feared enemies on the roads. On this page we let you know everything (absolutely everything) that the DGT and other agencies manage to control speed, the types of radars and radar detection systems. Go for it:

Index of contents

How does a radar work?

How does a radar manage to photograph a car or motorcycle traveling at more than 200 kilometers per hour at the right moment? Everything is achieved thanks to the Doppler effect. The kinemometer antenna emits a signal continuously with a predetermined wavelength. When colliding with a solid object, it changes its frequency and alerts that something strange is happening.

This wave is prepared so that, according to the variation of the frequency that occurs, the speed at which the vehicle circulates is detected. If it is greater than that programmed for that radar, the photograph is triggered in thousandths of a second.

Types of speed cameras

speed cameras fine

Types of radars according to their operation

Currently there is a wide variety of devices to collect data on the state of traffic (detectors). Most of them are capable of measuring the number of vehicles (intensity), the speed of circulation, the type of vehicle (light or heavy) and the occupation of the road as a percentage of the time of presence. This section presents the different technologies to collect these parameters, their advantages and disadvantages.

#1 Inductive loop

Inductive loop detectors are based on the principle of electromagnetic induction. Cuts are made in the pavement in the form of 2 m squares. sideways with a 7mm diamond tooth saw blade. ,

a coil is created by burying the wire in those cuts and then filled with epoxy resin or similar.

When a vehicle passes, its metallic mass induces a current that is interpreted as the passage of a vehicle. The duration time of the current is used to measure the percentage of occupation of the road. To calculate the speed of the vehicle, two close turns are placed at a known distance (for example, 2 meters), and by recording the start of the induced current in both turns, (times t 1 and t 2 ) the speed calculation as V = Distance / (t 2 — t 1).

Double loop detectors also measure the length of the vehicle and from that length it is classified as light or heavy. This type of inductive loop detectors are the ones with the greatest presence in Spain, since it is a highly developed technology, simple to operate, unaffected by environmental conditions and low installation cost. However, against them is their complicated replacement in case of breakage, their need for regular calibration and the “dam” effect they exert on draining pavements.

#2 Artificial vision

Its operation is based on the treatment of images captured by a television camera, obtaining the same traffic parameters as with double inductive loop detectors. The images from the camera are digitized and processed by algorithms that identify changes in the background of the image, determining if a vehicle is in the analysis area. From the analysis of

successive images, the intensity, speed and length of the vehicles can be determined.

The great advantage of this type of detectors is the possibility of using the slow video image in case of incidents, the possibility of automatic detection of incidents, they are not intruders on the road pavement, they do not suffer wear due to the passage of vehicles or for road maintenance work, have a high degree of reliability. On the other hand, it has a high installation cost, it requires

a vision cone as perpendicular as possible to the area to be measured and its operation can be altered by the visibility conditions of the road (

fog, night…) and generally a single camera measure a lane.

#3 Microwave radar

Microwave vehicle detectors emit energy at high frequencies (10.525 GHz in the US) in the direction in which the vehicles are moving. They detect the intensity and speed of the vehicles by the change in the frequency of the emitted signal due to the Doppler effect, which is proportional to the speed of the vehicle.

In their favor, it should be noted that they are transportable and measure speed with great precision, they are not intruders on the road and they work well in adverse weather, but against them they have to in the case of stopped vehicles

or with low speed (< 10 km/h) the data it gives us is as if the road were empty.
There are already true presence radars on the market that eliminate this disadvantage, measuring intensity even when traffic is held up and require one device per lane.

#4 Infrared

Infrared detection systems are based on the use of a photon sensor placed on a post or bridge next to the lane to be monitored and which measures the energy in the infrared band emitted by the road. When a vehicle enters the detection zone due to the heat of the vehicle it causes a change in the radiated energy. In this case we are dealing with a passive detector that only

measures the intensity.
If the detector also emits energy in the infrared spectrum (approximately 0.9 microns in wavelength), a portion of this energy will be reflected when passing vehicles and thus we will also measure speed, we are dealing with an active detector.

These types of detectors are not intruders on the road, but they have not become very popular due to their low accuracy and do not detect vehicles at low speed.

#5 Ultrasound

Ultrasonic detectors emit sound waves perpendicular to the road. The presence of a vehicle is determined by the difference in time for the reflected wave to arrive if it does so on the pavement or on a vehicle. The frequency of the emitted waves is located in the range of 25 to 50 KHz, above the audible frequency band. They are very sensitive to temperature and wind detectors, but in their favor they are very easy to install.

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#6 From magnetic pickup

They detect the distortion of the magnetic field produced by the passage over them of a metallic mass. They are made up of a metallic tube inside which there is an iron core with a coil connected to an amplifier. The normal ones are not capable of detecting the direction of movement, so they were improved by building the so-called compensated magnetic detectors, made up of four cores, which make it possible to distinguish the direction of movement from


From the creation of materials sensitive to the earth’s magnetic field, detectors based on it have been achieved. The sensor is normally formed by a block of about 15 cm. long and with a square section of about two or three cm. installing itself in the center of the rail, connecting by means of a cable to the converter amplifier. This type of detectors have the advantage of being easy to replace the sensor and being passive, so they do not influence each other in the case of proximity, and their range can also be adjusted (about 7 m.) On the contrary, they are seriously disturbed by power lines, rails or trams and its field of

action is not very defined.

The famous average speed radar on the Coruña highway, which will be active from March 16, will measure the average speed of vehicles traveling from kilometer 7 to kilometer 29 of the A6, and may be fined if the average speed resulting from the weather elapsed from the passage through the first radar to the passage through the last, exceeds the speed allowed for the section.

Types of radars according to their location

traffic cameras

#1 Fixed speed cameras

The DGT also defines them as cinemometers without an operator . They are those devices that are located in cabins and that can be placed on gantries, poles, roadsides or even cars and helicopters. Let’s see the types of fixed speed cameras that currently exist:

  • Gantry radar : They are fixed and are placed on the gantries or information panels of highways and highways. They normally control the speed of vehicles traveling in the left lane.
  • Stage radar : They are the last to have come into force and, using two cameras, they measure the speed of your car between two points. At the moment, they are, above all, in tunnels like the one on the A-6, in the Guadarrama tunnel; another on the A-7, in Torrox -Málaga-; on the A-7, in San Juan -Alicante-; on the AP-9, in O Sartego -La Coruña-…
  • Cabin radar : They are fixed and you will find them at the edge of the road, in the median or, even, next to panels or porticos -on the right side of the road-. There are them on dual carriageways and motorways, but also on secondary roads.
  • Pole radar : There are very few, and they are almost always installed in cities -on the road, they are residual-. They are located at the edge of the road and have a characteristic appearance: shaped like a post and a box on top.
  • Traffic Light Radar : Placed at traffic lights in cities. They capture the vehicles that pass the traffic lights in the red phase.

#2 Mobile radars

On the highway, you will find them on the shoulders or behind signs, level crossings or on top of bridges. The Multanova and the Autovelox can be placed in vehicles, both police and camouflaged. The Autovelox model cannot fine from moving cars.

Types of radars according to their placement

traffic cameras

Below we detail a list of the types of radars that the DGT uses to prosecute offenders of road regulations. For the moment, these are the types of speed cameras that the DGT uses to penalize drivers who exceed speed limits:

#1 Helicopter

The Pegasus helicopter is a radar developed with military technology that can be adapted to work in DGT helicopters. You can measure the speed of each vehicle from the air and penalize it if it exceeds the established limit. To do this, it has two cameras: a panoramic one, which records the vehicle on video, and another that photographs the license plate.

How does it act? Always from the air, at a height that can range from 300 m to more than a kilometer. Pegasus is capable of measuring speeds of up to 360 km/h -other radars do not usually ‘see’ cars above 300 km/h-, but it needs to follow the vehicle for a minimum of nine seconds to calculate its average speed.

In the event that this average exceeds the maximum speed allowed, you will be penalized. The fact of needing those nine seconds means that it is used on straight roads, to prevent the driver from braking before a curve, for example. In addition, it does not work either at night or in bad weather.

How to distinguish it? It is complicated, because it usually flies at a high altitude and focuses on the rear of the cars. In addition, it is undetectable by any type of detector or inhibitor. In any case, be suspicious of their possible presence if you see a DGT helicopter fly over – they are painted blue and yellow.

#2 Laser Gun

Radar laser gunThis is a kind of gun that, held by an agent by hand or resting on a tripod, is capable of measuring the speed of each car.

How do they act? Oriented towards the road, they can ‘hunt’ you from the front or once you have passed them, since they send a laser beam towards the vehicle and calculate the speed by measuring the time it takes to return the laser beam to the gun.

How to distinguish them? They are as difficult to locate as tripod radars.

#3 Tripod

resource 2 These radars are simply installed on a tripod, so they take up very little space. This allows them to be hidden very easily and placed in unusual places -for example, behind vehicles… or, even, they can be fixed to the guardrail itself-.

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How do they act? It depends on the type of radar. If they are of the Autovelox model -the most common as a tripod-, they can fine you when you pass in front of them… since, oriented towards the road, they emit two laser beams in parallel and measure the time it takes to cross them -and, thus, your speed-. Other tripod speed cameras work like a ‘fixed’ speed camera: they will fine you when you pass them.

How to distinguish them? They are very difficult to locate, since they can be hidden very easily and many times you will not even see that they have ‘hunted’ you. Even so, the most common thing is that they are placed behind hedges or bridges, behind guardrails, on bridges, behind bus shelters… Be suspicious if you see a vehicle parked on the shoulder: the tripod itself may be located nearby.

#4 Vehicle

Radars can be placed on police vehicles or on “disguised” vehicles. Let’s see both:

  1. Police vehicles : These are vehicles, clearly identified as DGT or Municipal or Local Police vehicles, which are equipped with a radar system. The most common is that they are parked on the shoulders of the road, on the sidewalks, behind bridges or bus shelters… The most used models are minivans -mainly Fiat Ulysse and Citroën C8-, Peugeot 307 and 407, Citroën Xsara Picasso, Toyota Land Cruiser… The radar can be of the two types that are used in camouflaged cars but, in addition, they can use a third type of radar that is located on the roof, next to the siren, and that will “hunt” you. once you’ve passed it.
  2. camouflaged vehicles: They are ‘street’ cars, without any sign that identifies them as Traffic or Municipal or Local Police vehicles, but which are equipped with a radar system. They act in two ways: the first is by driving at the speed limit or slightly below, to ‘hunt’ you when you overtake them. The second is by staying parked on the side of the road; It is normal for them to be on the shoulder, but it is also common to find them parked behind bridges, at tunnel exits, behind the hedges in the medians. The Civil Guard has about 120 radar cars. The most used models at present are: Nissan Qashqai, Peugeot 307 and 407, Toyota Corolla and Avensis, Opel Insignia, Citroën C5 -of the current and previous generation-, Ford Mondeo and Focus -of the previous generation-, Seat Exeo and Altea, Renault Mégane -previous generation, above all, Sedan- and Laguna or Mercedes C-Class. Most are silver, followed by whites, dark greys, blacks and dark blues. Depending on the type of radar they carry, you will distinguish them because they have a black hemisphere installed on the front -Multanova system or by waves; it will “hunt” you once you have passed it – or for having one of the rear windows lowered to install the radar -Autovelox or laser system on it; it will measure your speed when you pass at its height. You will distinguish them because they have a black hemisphere installed on the front -Multanova system or by waves; it will “hunt” you once you have passed it – or for having one of the rear windows lowered to install the radar -Autovelox or laser system on it; it will measure your speed when you pass at its height. You will distinguish them because they have a black hemisphere installed on the front -Multanova system or by waves; it will “hunt” you once you have passed it – or for having one of the rear windows lowered to install the radar -Autovelox or laser system on it; it will measure your speed when you pass at its height.

Types of fake speed cameras

Traffic lights with embedded gadgets, a suspicious steel booth on a highway platform, cameras behind porticos… I’m sure you’ve sometimes noticed the presence of these devices when you’re traveling by car. Fear not, because they are the so-called “false” radars, that is, they are other devices whose function is quite different from that of photographing and capturing a traffic violation.

Surely on more than one occasion you have been startled when you were traveling by car when you saw something strange and that caught your attention within the infrastructure of a city or a highway. The first thing you think is: “wow, another radar!” Well, fear not because they are not really radars.

These “fake” radars are actually another type of device with a very different function. The problem is that its design and placement can be misleading due to its resemblance to real radars. Below, we show you the most common examples of these “fake” radars.

#1 Speed ​​warnings

They are devices that are usually placed at the entrance to certain cities or residential areas. In these cases, the speed limit is usually 50, 30 or 20 km/h, depending on the case, so capturing the speed of a vehicle is a warning that it may be traveling above the established limit.

#2 Cabins on the sides of a road

Their shape, placement, and even the material with which these cabins are built are practically identical to those of the cabins that actually keep a radar inside. The significant fact that makes it possible to differentiate some booths from others is the lack of a hole or hole through which the camera lens would find the light to capture the offence. Therefore, this first case of “false radar” would correspond to a closed cabin, although it is true that many of these cabins are placed in a certain place for a future installation of a real radar, for which reason Traffic operators would have to go to install the radar with its corresponding photographic equipment and, therefore, make a series of holes on the outside of the cabin.

#3 Cameras on top of lampposts, walkways, porticos…

These cameras are the most confusing. To really see where the fixed radars are located, the DGT website itself provides a list of radars (Where are all the radars), so many of these cameras that we are talking about do not correspond to the real radars, but which are traffic capture/counting cameras, that is, they record the number of vehicles that pass through a certain road at a certain kilometer point.

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#4 Photovoltaic cells on streetlights

There are many lampposts in cities and various roads that are equipped with small photovoltaic cells. They can be confused with a radar, but they really fulfill a very different function as a power supply for the streetlight to illuminate when daylight disappears.

#5 Weather stations

The most usual of this type of devices is that they are placed on both sides of the road. Its shapes can also be misleading and can be installed on a portico, a vertical sign and even on lampposts. One of the hallmarks of these weather stations is that they are equipped with small solar panels, which allow them to capture solar energy and transform it into electricity so that it can be used to function.

#6 License plate readers

License plate readers are also part of the infrastructure of many highways. Most often, they are placed meters before crossing a toll road. The same thing happens at the entrance to a paid airport car park, since they are used to read the license plate and record the exact time the vehicle in question entered the car park.

types of radar waves

Name of the band frequencies wavelengths Observations
L 1-2GHz 15-30cm High distances, traffic control en route
S 2-4GHz 7.5-15cm Surveillance at intermediate distances. Terminal traffic control. weather conditions over long distances
x 8-12GHz 2.5-3.75cm Missile guide, meteorology, medium resolution cartography, airport surface radars. Tracking at short distances
ku 12-18GHz 1.67-2.5cm High resolution cartography. satellite altimeters
k 18-27GHz 1.11-1.67cm Absorption of water vapor. It is used for meteorology, to detect clouds. Also for motorist speed control.
Ka 27-40GHz 0.75-1.11cm Very high resolution cartography airport surveillance. Used to trigger cameras to photograph license plates of offending cars
W 75-110GHz 2.7 – 4.0mm It is used as a sensor for experimental autonomous vehicles, high-resolution meteorology and imaging.

Speed ​​camera database

It is increasingly common to find speed cameras on the road. To locate where they are, the best thing to do is to look at them directly on the website of the person who puts them up, right?

traffic radars dgt database

Speed ​​camera detection systems

Currently there are 3 different radar detection systems: those known as radar detectors, GPS technology systems and laser jammers.

#1 Radar Detectors

Radar detectors are the best known category within radar detection systems. They track the bands used by wave radars and warn when they detect a signal. There are two types of equipment: fixed and portable. Currently the law in Spain, after the last change in legislation, says that the purchase, sale and possession of a radar detector is once again illegal. It must be taken into account that radar detectors manufactured for the American market (Cobra, Whistler, Uniden, Rocky Mountain, etc.) are not effective in Spain, as the frequencies and powers are different.

  • Fixed radar detectors : They are installed in the front of the car. They have the advantage that they are hidden and the detection distance is greater. But it is very important that the installation is correct, to avoid interference with metal parts of the car or cables.
  • Portable radar detectors : They are attached with suction cups to the windshield of the car, attached to the dashboard or attached to the sun visor. They are usually connected to the cigarette lighter of the car. They have the advantage that they can be removed very easily and change cars, but remain visible. If the car has athermic windows, its use is not recommended, as the windows filter the radar signal.

#2 Laser Jammers

Completely illegal. Its installation in the vehicle is intended to interfere with the signal emitted by the radar, preventing it from being able to detect the speed at which it is driving. Being discovered with a device of this type is punishable by a fine of 6,000 euros and the withdrawal of six points from the license. Likewise, the establishments or persons in charge of its installation can be sanctioned with up to 30,000 euros.

#3 GPS alerts

Like navigators, these teams know the position of the vehicle through a GPS system (by satellite). They have a database with the position of the radars and when the vehicle approaches one of these radars, they notify the driver. They have the advantage that they warn well in advance (500 meters) and their use is also legal. But they only warn of the radars registered in the database, which are usually the fixed ones. Therefore, the most important part of this team is its database, which must be updated periodically.

GPS detectors or locators are equipment dedicated exclusively to the function of warning about radars and other points of interest registered in the database. They are not navigation systems. Some navigators, PDAs and GPS phones allow the user to load a database with the location of speed cameras. Such databases are often available on the Internet, but you must make sure that they are reliable and that your computer allows you to load them.

Curiosities about speed cameras

  • Fixed radars measure and photograph up to two cars per second without error.
  • The fixed speed cameras have a maximum error of one percent and the mobile ones usually regulate about 10 percent above the limits established on the road.
  • Portal radars only measure the speed of vehicles driving in their lane, while box radars can be programmed to measure in both directions. The side cabs can measure the speed of any lane.
  • The radars are not operational in extreme temperatures: below 10 degrees and above 60 degrees.
  • The radar photo is invalid if the license plate, make or model of the vehicle is illegible or unrecognizable or multiple cars appear in the same image.
  • It is false that the plastic license plates reflect the light of the flash and obscure the photo of the radar.

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