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Many accident reconstructions rely on the use of friction factors for the analysis of vehicle speeds. Measurement of the friction factor, or coefficient of friction, at the accident site is usually an important step in achieving a more accurate estimate of the friction factor at the time of the accident. Over the years several on site test methodologies have emerged within the accident reconstruction community. However, little has been published which compares the data and results from the different methods. This paper presents a comparison of some methodologies. A g-analyst1 accelerometer, a VC•20002 accelerometer, and a bumper chalk gun3/radar gun4 are compared for locked wheel friction values under different speed and road surface conditions. Data from the two on board systems are recorded simultaneously. Measurements are made for several stops at each of the speeds and two road surface conditions.

Accurate scene diagrams are essential to most accident reconstructions. Moreover, the scene diagrams make useful trial exhibits. Electronically Aided Survey Equipment (EASE) can aid the investigator and reconstructionist because it provides the following advantages over traditional measurement techniques: it is faster; it is more accurate; it eliminates transposing errors; it provides elevation measurements; and it permits data to be directly imported into CAD or animation programs. This paper will describe the process from survey to diagram. Furthermore, reconstructionists can load data into a spreadsheet for greater analysis. This paper will additionally cover how electronic survey and data logging can be useful in photogrammetry, in photographic reverse projection, and in obtaining elevations, roadway grades, cross slopes and curve radii for use in speed analysis. A discussion of sight distance analysis diagrams as constructed from survey data is also included.