Department of Civil Engineering, University of Louisiana at Lafayette, Lafayette, Louisiana.
Special Studies, Louisiana Transportation Research Center, Baton Rouge, Louisiana.
Traffic Inj Prev. 2024;25(3):544-552. doi: 10.1080/15389588.2024.2314596. Epub 2024 Mar 4.
Cable median barriers (CMBs) are installed on freeway medians to prevent cross-median crashes and reduce the severity of median-related crashes. Though CMBs are effective in preventing cross-median crashes, they are also known to increase the number of property damage-only (PDO) crashes. The higher frequency of PDO crashes could result in increased CMB maintenance and repair expenses. The aim of this study is to evaluate the safety impact and economic justification of CMBs in Louisiana.
Initially, a flowchart was developed using Louisiana crash data to identify targeted crashes, such as median-related and cross-median crashes. This was followed by a 3-year observational before-and-after crash analysis with an emphasis on head-on collisions and crashes involving large trucks. Using a 4-step improved prediction method, crash modification factors were then developed to quantitatively assess the impact of CMBs on crash outcomes, accounting for and adjusting to changes in the annual average daily traffic (AADT) and relevant crash frequencies before and after CMB implementation. Finally, an exhaustive benefit-cost analysis was conducted to determine the cost-effectiveness of CMBs.
The results revealed that CMBs significantly reduced cross-median crashes of all severities. However, an increase in PDO crashes was observed in both total and median-related crashes. Large truck cross-median crashes and head-on collisions also decreased significantly after CMB implementation. Testing Level 4 (TL-4) CMBs were found to be more effective in preventing vehicles from crossing the median and in reducing crashes of higher severity levels. The benefit-cost ratios, calculated using economic crash unit costs for both total and targeted crashes, were greater than 1. Notably, the estimated benefit-cost ratios were considerably higher, demonstrating that CMBs are cost-effective countermeasures for enhancing traffic safety.
This study contributes to the understanding of CMB performance from both traffic safety and economic perspectives. The findings may assist transportation agencies in making decisions regarding the management of CMB systems. Based on the comprehensive analysis of CMBs on Louisiana freeways, this project has revealed that CMBs are an effective and economically justified crash countermeasure. Thus, further implementation of CMBs is recommended until better alternatives are available.
在高速公路中央分隔带安装电缆中隔带（CMB），以防止对向碰撞和降低与中央分隔带相关的碰撞的严重程度。虽然 CMB 能有效防止对向碰撞，但也会增加仅造成财产损失的碰撞（PDO）的数量。更多的 PDO 碰撞可能导致 CMB 的维护和维修费用增加。本研究的目的是评估路易斯安那州 CMB 的安全影响和经济合理性。
最初，使用路易斯安那州的碰撞数据制定了一个流程图，以识别目标碰撞，如与中央分隔带相关的碰撞和对向碰撞。随后，进行了为期 3 年的观察性前后碰撞分析，重点是正面碰撞和涉及大型卡车的碰撞。使用 4 步改进的预测方法，开发了碰撞修正因子，以定量评估 CMB 对碰撞结果的影响，同时考虑并调整 CMB 实施前后年度平均日交通量（AADT）和相关碰撞频率的变化。最后，进行了详尽的成本效益分析，以确定 CMB 的成本效益。
结果表明，CMB 显著降低了所有严重程度的对向碰撞。然而，总碰撞和与中央分隔带相关的碰撞中都观察到 PDO 碰撞的增加。大型卡车对向碰撞和正面碰撞在 CMB 实施后也显著减少。测试级 4（TL-4）CMB 被发现更有效地防止车辆越过中央分隔带，并降低更严重程度的碰撞。使用总碰撞和目标碰撞的经济碰撞单位成本计算的成本效益比均大于 1。值得注意的是，估计的成本效益比高得多，表明 CMB 是提高交通安全的具有成本效益的措施。
本研究从交通安全和经济角度对 CMB 的性能进行了探讨。研究结果可能有助于交通管理机构在管理 CMB 系统方面做出决策。基于对路易斯安那州高速公路 CMB 的综合分析，本项目表明 CMB 是一种有效的、具有经济合理性的防撞措施。因此，建议在更好的替代方案出现之前，继续实施 CMB。
