The experimental and case study of needle marks on the speedometer as the physical evidence for the collision speed analysis.

The collision speed is important in accident analysis, and needle marks can be helpful as the physical evidence. The deceleration impact system has been built to analyze the mechanics of the needle and the gauge plate. Two isolated groups were designed to record the speed values under the same sample labels from real crashes. The visualization platform was built for the first group to collect needle marks. The second group recorded the speed values by other methods. The collision deceleration, the gauge plate materials, and the collision directions determine the forming of the needle marks. There were eight positive results from the 23 effective samples (12 frontal, four side, and seven rear), with discernible tip and/or middle marks on gauge plates. Multiple marks have been distinguished effectively. The low- and high-speed impacts have no obvious differences for real needle marks. It is more accurate for frontal impacts.