杭州发生的富家子弟撞人案后，对于发生车祸时的改装车辆的车速，前后不一。在网上查找了一下，找到了这篇关于车祸中计算车辆撞人时的速度估算或计算论文。有心的人可以翻译一下，初步看了，专家最后给出的结论基本符合，不是很离谱。因为影响车祸事后测算车速的因素很多，所以专家给出的速度基本可以接受。下面是几篇关于估算方法的英文文章摘要，附链接。
车辆与行人相撞：对行人的影响和预测的验证模型
Vehicle–pedestrian collisions: validated models for pedestrian impact and projection
式中：S-制动距离；V-速度；254-系数；F-摩擦系数；F的取值（结 冰0.10 积 雪0.20 湿 水 泥0.30 湿 柏 油0.40 干 柏 油0.60 干 水 泥0.70）
Confidence limits for impact speed estimation from pedestrian projection distance
Abstract: A key element of study of the biomechanics of pedestrian injuries from vehicle collisions is the determination of pre-impact vehicle speed. Pedestrian projection distances are an important means to determine collision speed, particularly as tyre brake marks are not readily observable with ABS brakes. A number of models have been developed by the authors, which include recent analytical models for forward [1] and wrap projection [2] impact. These models are novel as they include explicit modeling of the impact phase. They have been validated against the available test data, showing very good comparisons, and are therefore ideal for further statistical analysis. Confidence limits for speed estimates are set out for various purposes including injury research and litigation. The models show that the distribution of predicted collision speeds from projection distance can be large when a high degree of confidence is required. Some of this uncertainty is due to the impact phase where parameters such as duration and restitution are unknown for individual collisions, in addition to other confounding factors that are difficult to quantify. However the effects of the coefficient of retardation during the projection phase and the mass ratio between pedestrian and the striking vehicle can be readily determined. This paper analyses the influence of reduced variability of the input parameters on the predicted range of impact velocities. Analysis for known coefficients of retardation and mass ratio values yields the minimum prediction uncertainty due to the variability of the impact phase parameters alone. Results show that significant improvements in prediction uncertainty can be achieved by exact knowledge of the pedestrian to vehicle mass ratio and of the coefficient of retardation between the pedestrian and the road surface. In practice, while the mass ratio can be determined for individual collisions there is significant uncertainty as to the coefficient of retardation values, as these are influenced by the kinematics of the pedestrian during projection and ground impacts, in addition to factors such as road surface condition and contamination. However, overall data is available for wet and dry road conditions. Tables are presented for impact speed prediction from projection distance for various conditions and confidence levels.
Key words: Pedestrian collisions, throw distance, prediction uncertainty, confidence limits
关键字：行人碰撞，抛出距离，预测不确定性，可信区间
英文论文地址：http://www.tcd.ie/bioengineering/documents/JOURNA1.PDF
