It is important to remember that the police vehicle MUST pass between the same points as the target vehicle. This is essential as the distance information is taken from the police vehicle. When the police vehicle has travelled between the two points and the distance switch operated, on at the first point and off at the second point, the device then knows the distance between the points.
As the target vehicle travels between the same two points, the time switch is operated. The switch being switched on at the first point and oft at the second point. The device now knows the time the target vehicle took to travel between the two points. The device now has both parts of the equation required to calculate the target vehicle's speed.
This is done in a fraction of a second and visible on a digital display. If for any reason the operator has any doubt as to the validity of the check, it must be aborted. This type of check is carried out when the police vehicle is following the target vehicle.
As the target vehicle passes the first reference point, the time switch is turned on. As the police vehicle passes the same reference point, the distance switch is turned on. As the target vehicle passes the second reference point, the time switch is turned off. The device now knows the time the target vehicle took to travel between the two reference points.
As the police vehicle passes the second reference point, the distance switch is turned off. The device now knows the distance between the two reference points that the target vehicle has travelled. This check is carried out when the police vehicle travels between the two reference points. Turning the distance switch on at the first point and off at the second point. The police vehicle then parks in a position that the two reference points can be clearly seen by the operator.
As the device knows the distance between the reference points, as a target vehicle passes between the points the time switch is turned on and off. The device can then calculate the speed. Providing the distance information is not cleared from the device the police vehicle can remain parked and, by clearing the time information only, another target vehicle can be checked. This check is carried out when the police vehicle is travelling in front of the target vehicle, that is the target vehicle is approaching from behind at a speed which is excessive,.
The police vehicle will travel between the two reference points, turning the distance switch on and off. The device now knows the distance travelled. As the target the vehicle, still approaching from the rear, passes the same points the time switch is turned on and off.
The device now knows the time taken to travel between the reference points. The device knows the distance and time and can calculate the speed. NB When using this method operators should guard against any suggestion of being "agent provocateur". This check is carried out when the police vehicle is stationary at the mouth of a junction.
The target vehicle is seen approaching crossing the front of the police vehicle. As the target vehicle passes the front of the police vehicle the time switch is operated at an identifiable reference point. The police vehicle then moves off behind the target vehicle, operating the distance switch at the same reference point. With the police vehicle now following the target vehicle and both time and distance switched on, the completion of the check is the same as the follow check".
This mode enables a known distance previously measured by the device to be fed into the computer without the need to drive again over the route. NB Particular care must be exercised where shadows are used as these will change with the movement of the sun.
Simply record the distance on the same push button switches as used for calibration purposes. This procedure can also be used with the control module removed from the car and plugged into the portable battery pack.
However checks over a shorter distance, down to an absolute minimum of 0. Over short distance checks operators should consider other type approved devices that will provide a specific measurement.
In order to maintain accuracy these devices must be calibrated in accordance with the manufacturer's instructions. In order to establish the ongoing accuracy of the device a check MUST be carried out at the commencement of each tour of duty and at the end of that tour of duty if it has been used to detect an offence. If the device is found to be inaccurate, then not only must the defect be remedied but any offences detected since the previous accuracy check should be reviewed as it is not known at what point the equipment became defective.
It is recommended that all training be carried out using similarly equipped vehicles with car to car communications. At the conclusion of the course students should:- a Understand the principles and operation of the speed detection device s. Students will be required to perform five examples of each of the methods taught. See paragraph In the case of an unmanned device measurements are taken in respect of three vehicles on the film beginning - middle - end choosing clear images of the vehicle with defined edges to the frame.
The method adopted must be in accordance with manufacturers instructions and verified by P. NB In respect of the photograph measurement method the measurements should take place utilising an optical projector system not video with the assistance of a metal rule, digital calliper or the like duly certified by a trading standards office.
Specific Home Office circulars on the use of technology will be issued in due course which will deal with prosecution procedures to be followed by the police, Crown Prosecution Service and Magistrates Courts. ACPO policy in this respect already exists. However, new guide lines will have to be issued particularly in regard to the use of the conditional offer.
Presentation of evidence:- a The eventual success of any prosecution depends upon the accurate observations by the officer operating the device and the professional presentation of evidence before the court. With accurate sighting this problem is unlikely to occur. NOTE: The need to document all evidence is obvious as the memory of the operator must dim with the passing of time.
Corroboration is not required for photographic devices. The ACPO recommendations are that the duration of training should be a suitable period of time to enable an operator to qualify for the award of Certificate of Competence. This document has been prepared by ACPO Traffic as operational guidance which should be read in conjunction with manufacturers instructions. Where this differs or compliments the manufacturers instructions ACPO policy will take precedence. Police forces should liase closely with highway authorities in respect of installation, the ethos being to reduce casualty figures by means of influencing driver behaviour with a view to an overall reduction of accident figures.
In this respect forces should keep in mind the considerable benefit of media involvement by advertising their commitment to such schemes both on a local and force basis.
TRAINING This document should be used in conjunction with manufacturers instructions as the basis for training in respect of all road traffic enforcement technology equipment. The coverage of the radar depends on several factors, which include: a the radar power b receiver sensitivity c aerial characteristics and also d the size of the target vehicle e its distance from the observer f its position in the aerial beam 2.
Such persons shall keep accurate records which shall be open to inspection by the Home Office 8. The coverage of the radar depends on several factors, which include: a the radar power b receiver sensitivity c aerial characteristics and also d the size of the target vehicle e its distance from the observer f its position in the aerial beam. Presentation of Evidence a The eventual success of any prosecution depends upon accurate observations by the officer operating the device and the professional presentation of evidence before the Court.
Distance Time. The devices referred to in this document may be capable of producing evidence by means of photography. The absence of such a camera will in no way affect the type approval of the device should operation be decided upon in the non photographic mode.
Where such a camera has been attached the photographic elements of that system will require type approval. Should a camera attachment be utilised for evidential purposes then in the police manned mode one photograph will suffice.
If the device is unmanned then a second method of speed measurement is required thus providing a means of checking the accuracy of the device. The document sets out the type approval requirements with which the manufacturer will have to comply.
The camera attachment does not affect the procedures for the operation of the device concerned except that the camera should be in the operational mode to record the checking procedures on the photograph.
A check of the accuracy of the equipment should be carried out at the commencement and termination of each period of operation. Where the equipment concerned has to be dismantled and reassembled this should be at each site. In relation to equipment which does not have to be dismantled internal checks should take place at the beginning and end of the tour of duty and in any case where the equipment has been used every 24 hours.
As regards equipment which has to be dismantled the checks should take place at each site. Similar external checks should take place utilising a police vehicle fitted with a certified calibrated speedometer at speeds compatible with the site to be checked. These devices should be installed following consultation between the highway authority, manufacturers and the police and in accordance with guidance to be issued by the Home Office and Department of Transport. One such means offered by manufacturers at this time is the taking of two photographs of the offending vehicle at a known time apart.
Full details of the means of achieving this check are required by type approval to be included in the manufacturers instructions for the device concerned. This should take place in accordance with any instructions laid down by individual manufacturers. The legal requirement is that a notice of intended prosecution should be served within 14 days of the offence on either the driver or registered keeper.
As regards manned devices, films may contain details of offenders from differing sites on the same film due to the device being moved from site to site. Operators should ensure that the correct details of sites have been recorded both manually and on the photographs. This problem will not be evident until the film has been developed. Elapsed time is automatically recorded by the computer.
The officer measures the distance by throwing a switch when his car passes the first point and turning it off when the car passes the second point. The manufacturer's instructions MUST be adhered to in respect of switch operation and methods of calibration. However, as new equipment becomes available it will be evaluated by various forces and recommendations as to its suitability submitted to ACPO Standing Sub Committee on Road Traffic Enforcement Technology who will advise as to its future use.
A number of these devices are capable of being linked into video recording equipment. This in no way effects the operation of the device but merely provides pictorial evidence of that observed through the camera and evidence on tape of the operation of the time distance mechanism. It is imperative however that PSDB have approved the interface linkage between the device and the video.
Initially this was carried out by use of a certified stopwatch and the odometer of the patrol car. Whilst this principle remains, technology has allowed for the introduction of sophisticated equipment which has proved to be far more efficient and accurate.
The operation of the devices simply involves the operation of a distance switch and a time switch, in the appropriate sequence. This calls for a high level of accuracy and in order to achieve it, a good deal of practice is required.
The checking of a target vehicles speed can be done by a number of methods. Where a vehicle is, in the opinion of a police officer, travelling at an excessive speed the device is used as corroboration. In order that this can be done, the target vehicle needs to be checked between two reference points. The points used are best defined as "an identifiable point on or near the carriageway, either permanent or temporary:- a Which either casts a shadow so as to strike a moving vehicle, or which is so placed that the shadow of a moving vehicle strikes it or its shadow, or b where there is physical contact between the road wheels of the moving vehicle and a reference point e.
There are five alternatives:- i a moving shadow on a stationary object. By using reference points which fit this definition we can eliminate any uncertainty. Just a little note sent to me from a Traffic Officer. The Home Office allows a percentage of error for the overall check and this built into the operating procedure.
Each and every police officer undergoes an intensive training course to establish their margin of error. If it falls within the guide lines then it is "acceptable". So don't go using the info below unless you can prove your case without doubt. Once a distance is entered, the operator pushes a button to start then stop the stopwatch.
Reaction time is defined as "the time interval between an input signal physiological or a stimulus psychophysiological and the response elicited by the signal.
What is considered "normal" human reaction time? First, let's take a look at the best: Drag racers.
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