Asadollahi Pajouh Mojdeh, Julin Ramen D, Stolle Cody S, Reid John D, Faller Ronald K
a Midwest Roadside Safety Facility , University of Nebraska-Lincoln , Lincoln , Nebraska.
b John Deere Design Division , Des Moines , Iowa.
Traffic Inj Prev. 2018 Feb 17;19(2):219-224. doi: 10.1080/15389588.2017.1353687. Epub 2017 Sep 21.
Guardrail heights play a crucial role in the way that errant vehicles interact with roadside barriers. Low rail heights increase the propensity of vehicle rollover and override, whereas excessively tall rails promote underride. Further, rail mounting heights and post embedment depths may be altered by variations in roadside terrain. An increased guardrail height may be desirable to accommodate construction tolerances, soil erosion, frost heave, and future roadway overlays. This study aimed to investigate and identify a maximum safe installation height for the Midwest Guardrail System that would be robust and remain crashworthy before and after pavement overlays.
A research investigation was performed to evaluate the safety performance of increased mounting heights for the standard 787-mm (31-in.)-tall Midwest Guardrail System (MGS) through crash testing and computer simulation. Two full-scale crash tests with small passenger cars were performed on the MGS with top-rail mounting heights of 864 and 914 mm (34 and 36 in.). Test results were then used to calibrate computer simulation models.
In the first test, a small car impacted the MGS with 864-mm (34-in.) rail height at 102 km/h (63.6 mph) and 25.0° and was successfully redirected. In the second test, another small car impacted the MGS with a 914-mm (36-in.) rail height at 103 km/h (64.1 mph) and 25.6° and was successful. Both system heights satisfied the Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3) evaluation criteria. Test results were then used to calibrate computer simulation models. A mounting height of 36 in. was determined to be the maximum guardrail height that would safely contain and redirect small car vehicles. Simulations confirmed that taller guardrail heights (i.e., 37 in.) would likely result in small car underride. In addition, simulation results indicated that passenger vehicle models were successfully contained by the 34- and 36-in.-tall MGS installed on approach slopes as steep as 6:1.
A mounting height of 914 mm (36 in.) was determined to be the maximum guardrail height that would safely contain and redirect 1100C vehicles and not allow underride or excessive vehicle snag on support posts. Recommendations were also provided regarding the safety performance of the MGS with increased height.
护栏高度在失控车辆与路边障碍物的相互作用方式中起着关键作用。较低的护栏高度会增加车辆翻滚和翻越的可能性，而过高的护栏则会导致车辆钻入下方。此外，护栏的安装高度和立柱埋入深度可能会因路边地形的变化而改变。增加护栏高度可能有助于适应施工公差、土壤侵蚀、冻胀以及未来的路面加铺。本研究旨在调查并确定中西部护栏系统的最大安全安装高度，该高度在路面加铺前后都应坚固且保持防撞性能。
通过碰撞测试和计算机模拟对标准高度为787毫米（31英寸）的中西部护栏系统（MGS）增加安装高度后的安全性能进行了研究评估。对顶部护栏安装高度分别为864毫米（34英寸）和914毫米（36英寸）的MGS进行了两次小型乘用车的全尺寸碰撞测试。然后将测试结果用于校准计算机模拟模型。
在第一次测试中，一辆小型汽车以102公里/小时（63.6英里/小时）的速度和25.0°的角度撞击了护栏高度为864毫米（34英寸）的MGS，并成功改变行驶方向。在第二次测试中，另一辆小型汽车以103公里/小时（64.1英里/小时）的速度和25.6°的角度撞击了护栏高度为914毫米（36英寸）的MGS，测试成功。两种系统高度均满足《安全硬件评估手册》（MASH）测试等级3（TL - 3）的评估标准。然后将测试结果用于校准计算机模拟模型。确定36英寸的安装高度是能够安全容纳并改变小型汽车行驶方向的最大护栏高度。模拟结果证实，更高的护栏高度（即37英寸）可能会导致小型汽车钻入下方。此外，模拟结果表明，安装在坡度高达6:1的引道斜坡上的34英寸和36英寸高的MGS能够成功容纳乘用车模型。
确定914毫米（36英寸）的安装高度是能够安全容纳并改变1100C车辆行驶方向且不会导致车辆钻入下方或在支柱上过度受阻的最大护栏高度。还就高度增加后的MGS的安全性能提供了建议。
