It's topping the chartt in forensic labs . .
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ONE ASPECT of the tachograph that was constantly — and rightly — emphasised during its introductory period in this country was its potential as a management tool; the tachograph is more than just a costly, overcomplex electronic substitute for the humble log book.
Taking this principle a step further and really studying the tachograph chart, it is surprising just how precisely a vehicle's journey can be reconstructed. And it is this ability that is being increasingly used in the analysis of road traffic accidents where the vehicle is fitted with a tachograph.
Like a black box flight recorder in an aircraft, the instrument can be a source of factual, unbiased evidence. The fact that its information is not dependent on human observation or memory is important when one considers the frequent variance in witness reports or the different version given by parties involved in the same accident.
In West Germany, where tachographs in some form or other have been in existence for over 40 years, the use of tachograph charts in accident evaluation has been highly developed; the way has been lead by German tacho manufacturer Kienzle. This company now has 10 specialists who do nothing but accident analysis and who carry out a total of 3,000 detailed evaluations a year.
Their work is highly regarded by the West German police and courts; the information is officially rated as "expert evidence" and carries a lot of weight. if accident information derived from the subsequent tacho chart analysis contradicts a witness's observations then proof that the tachograph was not working correctly is required before its evidence is overruled in Germany.
About 18 months ago the British importers of Kienzle tachographs, Lucas Kienzle at Gravelly Industrial Park, Birmingham, sent its senior technical lecturer, Peter Needham, to study accident evaluation under the German Kienzle experts. Peter Needham is now responsible for providing a similar tacho accident evaluation service for Lucas Kienzle in the UK. To ensure the accuracy of his work every one of his evaluations has been sent to Germany for verification.
This may seem verging on overkill, but Peter Needham explained that detailed analysis of a tacho chart is rather more than a long, hard squint at the chart with the aid of a magnifying glass in a good light.
"It's not good enough just to put the chart under a microscope, either," he said. "You have got to know the tachograph inside out as well. Then you know what the instrument is liable to do in different circumstances and only then can you accurately interpret what you see on the chart."
To examine the chart Peter leedham uses a German-built jenzle microscope which gives magnification up to x30. This cale of magnification is necesary; the speed trace scribed on le chart by a modern sapphirepped tacho stylus is eight licrons wide. (A micron is one Alionth of a metre, equal to ne thousandth of a millimetre.) The chart is placed in the licroscope's finely engineered Jrntable, which can be rotated ) very small stages — each unit f rotation represents just one econd of time in the vehicle's )urney. As he looks into the nicroscope, superimposed on le relevant portion of the speed -ace is a finely scribed cursor sference line which is just three licrons thick. This remains xed while the chart on the Jrntable can be rotated second y second.
The basic procedure involves sading off the exact speed from he tacho chart at a point where he cursor line crosses the speed race. Then the turntable is noved by, say, 10 seconds and a econd speed reading is taken where the cursor line now rosses the trace. This therefore hows the speed of the vehicle 0 seconds after the first reading nd by taking a series of readlgs like this a detailed picture of he vehicle's progress immeditely before the accident can be puilt up.
In most cases Peter Needham s concerned only with the few ninutes before the accident — isually no more than 3,000m 1.9 miles) before the scene.
The readings are so accurate hat he plots the speed changes ounting back from the accident metres and seconds. He can pinpoint very subtle changes in peed to a particular point in ime or distance; such a change n speed may be very small but ufficient to show that a driver pad noticed something and aken some form of action.
Very often, what is just as important as absolute speed is the ate of change in speed, and the eries of readings taken by Jeedham will enable him to work out the exact rate of accel[ration or deceleration. It is exessive acceleration or deceleraion on a poor surface that is Pften a contributory factor in iccidents involving skidding or wk-knifing. Peter Needham will oon be using a computer to ase the acceleration/deceleation calculations.
Despite the high magnification still requires a great deal of lose examination to spot these peed changes — a momentary leceleration and acceleration will appear as a single line on the speed trace to all intents and purposes rather than two lines that are very close together.
To separate the lines on the trace, Peter Needham will use a prism on the microscope to split the light beam. Because the trace is actually a tiny groove in the recording layer of the tacho chart, the light from the Vshaped groove walls is not reflected into the microscope eyepiece — only the centre of the groove shows up clearly as a silver line.
Helping Peter Needham make the evaluation is a x10 magnified photograph of the speed trace. On this he will mark the precise speeds at certain points; these speeds may or may not confirm the reading shown by the tacho chart's own concentric speed rings.
At the precise moment of impact in an accident the speed trace normally deteriorates into a jumble of lines when viewed under the microscope. A notable exception to this is when the vehicle turns over or its wheels leave the ground; as soon as this happens the wheels speed up and the speed trace will shoot upwards off the top of the chart in what appears to be a vertical line.
Having carried out the analysis of the chart, Peter Needham has to present his findings. The report he completes will contain four main parts.
Rirstly, there will be the x10 magnified photograph with the speeds at relevent points picked out. Secondly, there will be a table showing the precise speed at 10-100m intervals immediately before the accident and and whether the vehicle was accelerating or decelerating since the last measurement.
Thirdly, there will be a graph of speed versus distance, graphically illustrating the information in the previous table metre by metre, second by second.
Finally, the report will include a short, written explanation of Peter Needham's findings. He will not draw conclusions, merely state what the chart reveals.
The report will end with the qualification: "Subject to correct calibration." This is because all the information from the chart depends on the tachograph/vehicle being correctly calibrated. And before the chart is even put on the microscope turntable Peter Needham needs a lot of background information.
A standard form must be completed given details such as the type of vehicle/trailer, laden or unladen, road and weather con ditions etc. The driver's statement and sketch plan of the accident is necessary and the police report also useful. The chart itself must have been signed at the accident by the police or independent witness.
Lucas Kienzle offers two levels of accident evaluation. The first type is as previously described where just the chart is analysed — this accounts fo 80 per cent of the cases. The second type is even more thorough and nearly always used when the case is going to court. This is chart and vehicle accident evaluation, entailing the re-calibration of the vehicle's tacho to ensure that the traces are absolutely valid.
This re-calibration can show up errors such as the speed trace at Om ph not being exactly on the base line and so giving a reading slightly higher or lower than the actual speed. Ordnance Survey maps are also used to determine and verify distances and gradients, etc. Peter Needham is doing around four accident evaluations each week. The basic chart evaluation, including the preliminary setting-up and the writing of the report usually takes him about four or five hours and costs £60-E70. The more comprehensive chart and vehicle accident evaluation takes around two days and the charge is therefore higher at E1604200. This may sound costly, but if a hefty insurance or damages claim is dependent on the outcome it may turn out to be money well spent.
The speed of the accident evaluation service will soon be bettered because this month Peter Needham completes his training under the German experts and so will no longer send his results to Germany for verification. This should reduce the turnround time for a chart from a month to two or three weeks.
Lucas Kienzle's accident evaluation service will also analyse charts for suspected falsification, speeding or driving efficiency and is currently handling six to eight such cases a week at a typical cost of £15 to £20 each. This work is seperate from the company's routine chart reading bureau service.
Having made the evaluation of the tachograph chart after an accident, what weight does this analysis carry and what does it prove?
At the outset Peter Needham stressed that he does not pretend that the evaluation is the complete answer; it is another source of information that can be used alongside the police report, witness observations and so on.
But to their credit the police are becoming increasingly aware of the potential of tacho charts in their own accident investigations. There are three Forensic Science Laboratories (Metropolitan, Birmingham and Strathclyde) that provide a tachograph chart analysis ser vice for the police forces in their areas. The Forensic scientists received their initial training with Kienzle in Germany and so work with the same techniques as Peter Needham at Lucas Kienzle. In the event of a fatal accident involving hgv or psv Peter Needham told me that the police will seize the tachograph chart and send it to one of these Forensic Science labs for evaluation. To help the police themselves understand tachographs more thoroughly there are six police regional tachograph training centres in England and Wales, running week-long courses for the local constabularies.
Peter Needham will evaluate only charts removed from Lucas Kienzle tachographs; he will not deal. with charts from Veeder Root or Smith tachographs. "I am not 100 per cent confident that I could do a sufficiently accurate evaluation on their charts because I don't know what tolerance their tachographs work to."
However, he will evaluate Lucas Kienzle pattern charts made by other chart manufacturers. He prefers the genuine article because he knows the accuracy of its printing and the quality of its coating — crucial at high magnifications. Although the tachograph chart evaluation evidence may be presented in court after an accident, nobody can say what effect it will have. It will be taken into account, and may be given added credence by the Forsenic Lab's use of the technique. However, the ultimate decision still rests with the magistrates and if they do not appreciate the significance of the tachograph evidence then the value of the analysis is severely reduced.
Peter Needham is personally carrying out about 200 accident evaluations a year and believes there is a market for around 1,000 a year in this country. Lucas Kienzle is optimistic about the future of this "science"; tachographs are firmly estab lished as a legal requirement and the police, Department of Transport traffic examiners and the operators themselves are realising the instrument's deeper potential. It will only be a matter of time, reasons Lucas Kienzle, before tachograph chart accident evaluation evidence here is regarded as highly as it is in West Germany.
• by David Wilcox