Speed Trap Detection

Given the governments trend for using automatic sped detection equipment the market place seems to have been flooded with all sorts of gadgets designed to help you avoid that dreaded speeding ticket. The most common of these is the Radar Detector.

Do they work? Yes, the modern radar detector is quite effective at alerting you to GATSO's, mobile GATOS's and Mr Plod standing behind a bush with a Radar Gun.

How do they work? To understand how a Radar Detector works, you must first understand how the radar based equipment used by Mr Plod determines your vehicles speed. A police officer will direct the gun at the registration plate, a flat reflective surface, of an approaching vehicle within 100-200 metres, the practical operating distance. The gun, at a nominal output of 10mW, will emit a radar beam, which can be simply thought of as a rapidly expanding cone from the gun. At 100m from the gun the width of the cone is 2m, which will thus allow the officer to target only the car in front of other cars. The gun receives a partial reflection from the target vehicle, which of course is of a different frequency than the one emitted. It is this change in frequency, which allows the speed of the oncoming vehicle to be measured accurately within 0.1mph. This is known as the Doppler Effect. It is the same basic principle for GATSO cameras. The Radar on the GATSO is directed across the road at a 20-degree angle. As you pass through the beam the radar is reflected back to the camera allowing it to calculate your speed. A Radar Detector is simply a receiving device. It "listens" for K band Radar in a given range. When it detects a radar based signal in the correct band, it alerts you to its presence. As not all the radar signal is reflected back, the detector can pick up on the signal that is still travelling towards it, some claim up to a mile from source. Personal experience has shown that they are very effective at a quarter of a mile from source.

What about false alarms? This is open to debate, some people say that radar detectors are a waste of time given the number of false alerts you receive. Firstly, only K band (24.075-24.125 GHz) and Ku band (10.700-18.100 GHz) radar is used in this country. K band radar is the predominant type used. It is used on fixed post GATSO's and hand held guns, it is also used on mobile GATSO's. Ku band is used for some mobile camera installations. However I believe that its use is now some what limited and is only presently used by forces in the Thames Valley area. X band radar is used for traffic lights and other equipment, as is Ka band radar. If you have an older detector, or one imported from the USA chances are that the X band radar detection will be enabled. This means your detector will alert you to the presence of every set of traffic lights you come across! A quality radar detector will allow you to choose which bands you want it to "listen" for. An all signing all dancing 5 or 6 band radar detector in this country will only be of use if you can disable all other bands except K and Ku Sadly though, automatic door openers on supermarket doors, shopping centres etc use radar based devices that are in the same frequency range as that which Mr Plod uses. So you will have to put up with the false alarms from these. However, they are not really false alarms, they are false positives. Your radar detector has only alerted you to the presence of a signal in the desired band, it only doing what it is designed to. Through personal experience I have found that Bel Radar/laser detectors are by far the best value for money devices you can buy. They have been by far the best devices in any tests carried out and although not the cheapest on the market they certainly do the job they are intended to do with great results time after time.

Below is a rough guide on what to expect for your money; Budget Radar detectors £50 - £100 I'd rather trust the neighbour's cat! Waste of money and only likely to inform you once you have been nicked. Unlikely to have switchable band features so expect a high number of false alerts Mid Priced detectors £100 - £200 Over £150 you will get a detector that will give you adequate warnings on hand held radar guns. Don't expect much more than a few seconds warning if any on GATSO installations. If it has a combined Laser detector don't trust it Mid to High priced detectors £200 - £250 Certainly any detector over £250 will be a worthwhile investment. This price range is where you start to enter the Bel range. A unit from the Bel range at this price will give more than adequate warnings on hand held guns and depending on the unit at least 11 - 15 seconds of warning on a GATSO installation. Doesn't sound much, but its enough time to react appropriately rather than suddenly slamming the brakes on which could lead to an accident. A unit in this price bracket that has a Laser detector built in is more likely to give you a warning. High Priced radar and GPS detection equipment £250 -???? Equipment in this range will certainly give adequate warning on a hand held radar gun. Detection on approach to a GATSO installation will vary from 20 seconds and upwards depending on the lay of the road and surroundings. A radar detector with laser detection capabilities will certainly be more likely to give an accurate warning.

What about laser guns? The word Laser actually stands for "Light Amplification by Stimulated Emission of Radiation." It is a form of electromagnetic radiation the same as radio and microwaves. The difference is that light has a much higher frequency than radio or microwaves. The light emitted by a laser is no different than any other source except that it has a unique method of generating light. The type of laser used is an infrared semiconductor laser diode. The generated light energy has a wavelength of approx. 900 nanometers, with a beam divergence of 3 milliradians, equal to a beam width of about 3 m (or ft) at 1000 m (ft). Target acquisition times range from 0.3 to 0.7 seconds. The same principles apply to laser guns as for radar guns. Mr Plod will target a flat reflective surface. The time taken for the light to be reflected back is used to calculate your speed. Normally Mr Plod will use one of these either mounted on a tripod or mounted in a vehicle. Some radar Detectors also offer laser detection. Most upmarket brands will have no problems in detecting residual laser signals.

GPS detection Equipment This style of "detector" is relatively new to the market. They differ form the normal style of radar/laser detector as they use the Global Positioning Satellite system to alert you the presence of GATSO installations. These do not detect the camera in the sense that a radar detector does. They use a database that contains the locations of know fixed camera installations. With most of these you can also add your own by the press of a button. Some offer the added benefit of having known blackspots as part of their databases, and also allow you to add your own. They can also contain locations of known frequent mobile and laser sites. The Morpheus Geodesy is now available with the optional radar detector, essentially giving you the best of both worlds. GPS based warning of camera locations and radar based warning if the camera is active or of Mr Plod with a radar gun.

Non-Radar/Laser based Police Equipment Of course Mr Plod has many other ways of catching you breaking the speed limit. There are many devices they can use which can measure the speed of you are travelling at. However there are to many to go into detail here so I shall cover the common ones you are likely to encounter. Most common of these is the VASACR unit. This can be used stand alone or linked to a video camera and recorder, also know as ProVida when used in this way. Its operation is very simple and relies on Mr Plod being able to see your vehicle pass to specific points on the road. The VASCAR unit is simply a timing device. Mr Plod will pick two static points on the road and simply time you between these. The distance between the two points is known and this along with the time it takes you travel between the two points is used to calculate your average speed. The VASCAR has two main methods of use: i) The Police vehicle will follow you over a given distance. Mr Plod will active the unit as you pass a static point on the road, as you pass a second static point the officer will deactivate the unit and it will calculate your average speed over the given distance. ii) The police car will travel a set distance and the VASCAR will be used to record the distance covered. They will the park the car somewhere and make it as hard as possible for you to see them in advance. They will then time vehicles over the distance set in the VASCAR and calculate your average speed. This is known as using Pre Fed data.

Can you detect VASCAR equipment? In a word, no. There is nothing you can do to detect the equipment in use, the only thing to do is hope for power failure in the police car! The points used for timing your vehicle can be any static point on the road the officer chooses. It can range form a bridge or road sign to specially painted markings on the road. Ever wondered what the white squares are painted on some roads? Now you now! They can use landmarks at the side of the road or even a shadow cast by a road sign or other large object! As long as the reference point is unlikely to move whilst you are being timed they can use what ever they like! Best defence? Keep your eyes open!!!

SPECS Still quiet new. Principles are the same as for VASCAR. Two cameras are installed on a road at a set distance apart. As you pass one camera it reads your number plate and stores it. As you pass the second camera it again reads you number plate and compares the time that has elapsed between the two readings and calculates your average speed. If your average speed is over the threshold set your nicked! These installations are very sneaky and highly accurate. They need no operator to come and empty a camera as the images are digital and sent direct to the processing office. They operate 24/7 in all weather conditions and can cope with thousands of cars in a day. GPS detection equipment is your best defence against these as they contain a database of the locations. Note: Due to different privacy laws in Scotland it is not legal to use these as they take a picture of the front of the car including the driver. This is just a very brief outline of what equipment the Police uses and how to try and avoid that ticket! I personally do not condone the use of excessive speed. However, given the right place and the right time, a bit of excess never hurt anyone if care is exercised. J If you really want to see how fast your car goes. Keep it to a track! For more information as well as pictures of equipment and reviews of detection equipment please visit http://www.ukspeedtraps.co.uk

kindly researched and sent in by Ken Smith, 3rd September, 2002