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Total station equipment, triangulation, or some other mapping technique can generate x-y coordinates describing curved tire marks on the pavement. These marks may result from a critical speed maneuver. Traditionally, these marks are assumed to follow a circular arc and a radius can be determined for use in the critical speed yaw formula. However, critical speed yaw marks typically have a decreasing radius in the direction of travel and a spiral is a more precise fit to the data. In this paper, a total least squares fitting approach is presented to fit the parameters of three types of spiral curves to coordinate data. These are a clothoid spiral, a logarithmic spiral, and an Archimedean spiral which are evaluated and compared for usability in a critical speed yaw analysis. A spreadsheet implementation is presented that makes use of the Microsoft Excel Solver Add-in to perform the minimization of the total least squares fit for the spirals.

Concepts of forensic soundness as they are currently understood in the field of digital forensics are related to the digital data on heavy vehicle electronic control modules (ECMs). An assessment for forensic soundness addresses: 1) the integrity of the data, 2) the meaning of the data, 3) the processes for detecting or predicting errors, 4) transparency of the operation, and 5) the expertise of the practitioners. The integrity of the data can be verified using cryptographic hash functions. Interpreting and understanding the meaning of the data is based on standards or manufacturer software. Comparison of interpreted ECM data to external reference measurements is reviewed from the current literature. Meaning is also extracted from interpreting hexadecimal data based on the J1939 and J1587 standards. Error detection and mitigation strategies are discussed in the form of sensor simulators to eliminate artificial fault codes.