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Accurately calculating speed from heavy truck skid marks can be difficult. As indicated in SAE article 910126“̈-.an accurate deceleration rate is often an elusive piece of the puzzle.” This paper is intended to add to work done by others in determining heavy truck deceleration rates and calculating speed from skid marks by using different deceleration rates through different portions of each skid length. Deceleration rates and skid lengths obtained from a test by the Washington Association of Technical Accident Investigators (WATAI)[2] will be used as a basis for an evaluation of the adjusted drag factor method for speed determination. The method is then used to compute truck speeds in a case in which a heavy truck left non-uniform skids of different lengths while braking and evasively steering.

This accident reconstruction is an actual case that went to trial in the State of Oregon. The motorcyclist (plaintiff) brought suit against the truck driver's employer (defendant). At the request of our client, the names of the individuals involved and the city or county, will not be referred to. Talbott Associates, Inc. were retained to do an accident reconstruction, including speeds, collision analysis and avoidability analysis. At the time of trial we proviced expert testimony. The vehicles involved were a 1982 Yamaha 750 motorcycle and a 1984 International cab over truck pulling a flat bed trailer. The truck was moving slowly eastbound along a two lane road, speed limit 45 mph, looking for a delivery address. The truck was turning left into an industrial area. The motorcycle was traveling in the opposite direction and had just passed another vehicle. The motorcycle collided with the truck and the motorcycle rider was fatally injured at the scene.

Testing was performed to determine the stopping characteristics for motorcycles using rear brakes only and front and rear brakes in combination. Information was used from SAE Paper 840250 to get stopping characteristics when a motorcycle is laid on its side. There were differences between rear brakes only, laying a motorcycle on its side, and front and rear brakes in combination.

An important issue in many vehicle accidents is to determine if the vehicles lights were on or off at impact. It may be the brake lights, signal lights, back-up lights, or headlights that are at issue. Review of the literature indicates that analysis of halogen headlights ace not covered in the detail of other lights. This paper will evaluate halogen headlights. Many indicators used to determine if lights are on or off at impact do not generally occur with halogen headlights. The filament is structurally stronger, and the filament envelope is rarely broken during impact. Included in this paper will be a brief theory on differences between standard lights and halogen lights. Several case studies will be evaluated and conclusions presented to determine if a halogen headlight was on or off at impact.