直行車與轉彎或迴轉車碰撞車速推估之研究

Impact Velocity Estimation of Straight Forward Car Colliding with Turning or U-turn Car

本文研究對向直行車與轉彎或迴轉車碰撞事故中，估算直行車在碰撞前車速的方法。將這類的碰撞事故視為二維垂直碰撞模型並以車損能量法來作分析。首先以四點量測法量測碰撞後車體殘餘變形量，並參考美國高速公路交通安全管理局(NHTSA)對各種車輛分類，提供相對應的剛度係數值來計算車損所吸收之撞擊能量，進而求出有效碰撞速度，再結合現場跡證如現場煞車距離、滑痕距離及撞擊位置等以估算未撞擊前速度。用車損能量法針對18件實際發生的事故作直行車之車速推估，同時亦以動量法推估並作比較。在這些案件中若是二部車碰撞後再去碰到其他車輛、安全島、地上建築物、水溝或其他突出物，在這種情況下用動量法作分析就會變得很困難，僅能用車損能量法推算直行車車速。結果顯示由車損能量法推估出的車速傾向會比動量法低。本文以動量法為基準，利用一修正因子對車體所吸收撞擊能部分，作適當修正，讓這兩種方法所得到之結果一致，並彌補動量法在碰撞事故分析上不足。

This paper presents a method to estimate velocities of straight forward cars colliding with turning or u-turn cars. We treat this kind of accidents as two-dimensional perpendicular impact and use crush energy method to analyze them. By integrating information of four residual crush distances of damage surface and stiffness coefficients provided by National Highway Traffic Safety Administration (NHTSA), we are able to obtain damage energy and effective impact velocity. Then based on the brake distance, brake mark and impact area data, the velocity of straight forward car before the impact can be estimated. We use 18 real cases to compare the velocities obtained by the crush energy method and momentum method. In these cases, if the cars hit other vehicles, safety island, building, gutter or bumpers, the momentum method may be inadequate while the energy method can be used to calculate the speed of the car. The results show that the velocities calculated by crush energy method are lower than that by momentum method. Based upon the momentum method, we use a correction factor to adjust the impact energy absorbed to enable the two methods to reach the same results. This can compensate the momentum method’s inadequacy in reconstructing some car accidents.