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<div class="section abstract"><div class="htmlview paragraph">The behaviour of the instrument cluster of passenger cars during a collision is reasonably well understood, following a number of studies over the past decade. However, one of the frequent questions asked is if motorcycle instruments can be considered in the same way as passenger cars. Motorcycle instruments work in the same way as passenger car instruments. The older models use a Bowden cable to drive a spinning magnetic cup, which drags an instrument needle against a hair spring. Newer models (typically post 2000) use a stepper motor which requires power to drive the needle to any indicated position, including returning it to zero. Hence if power to the instrument is lost as a result of a collision, there is no electrical power to the motor to move the needle, and it should be left at its last position before the power was lost. However, the accelerations experienced by a motorcycle instrument during a collision are significantly different from those of an instrument cluster housed within the dash of a passenger car. Over the past few years a number of crash tests involving motorcycles have been carried out in the USA and UK and the behaviour of the instruments were analysed to see how they perform at holding any residual reading.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Around the turn of this century, the automotive industry introduced a new type of technology to drive the gauges on a vehicle’s instrument cluster. The change was unannounced to the collision reconstruction world, but soon after, investigators observed a marked increase in crashed vehicles displaying frozen gauges at what often appeared to be correct readings. The new technology was the use of stepper motors which require power to return to the zero position. Hence if electrical power is lost, the gauges stop in position. There have been a number of previous papers covering the operation of the instruments and crash testing of cars and motorcycles to establish the ability of the instruments to withstand the forces on the instrument during a collision. This paper aims to compare the frozen instrument readings from real world collisions with the available EDR data from the crashed vehicles. With the assistance of the collision reconstruction community, a large dataset of 236 vehicles with frozen speedometer readings were compared with EDR and other corroborating methods. This paper reviews the current state of knowledge, compares the instrument readings of each of the 236 vehicles against the available EDR data or other corroborating method. It then assesses each case against the criteria proposed by Goddard and Price [<span class="xref">3</span>, <span class="xref">4</span>] to assess if the cases that are being filtered out for selection, are accurate readings. It was found the existing criteria was an effective filter in removing the majority of cases capable of producing erroneous readings. However, it was found that some erroneous readings were present in low speed impacts. With the addition of a minimum speed criteria, the likelihood of an erroneous reading was greatly reduced. At recorded speedometer readings over 80 Km/h, the corroboration with the EDR speed had a standard deviation of 4%.</div></div>