Abstract Fog is a weather condition that reduces visibility of the driving scene, while slow traffic may be formed due to the bottleneck on freeways. This phenomenon may lead to higher rear-end crash risk when vehicles approach slow traffic, since drivers might not observe the speed reduction ahead of them timely with the reduced visibility and could not have enough time to respond. This study aims to develop a variable speed limit (VSL) control strategy to reduce the rear-end crash risk at freeway bottlenecks under fog conditions. A VSL control algorithm was developed with consideration of the different relationships between the gap and visibility distance. The VSL strategy was also tested in the fully connected vehicles (CV) environment. A feedback control framework was developed to combine the VSL and CV control. The proposed VSL strategy was implemented and tested for a freeway section with a bottleneck through the micro-simulation software VISSIM and the intelligent driver model (IDM) was employed to account for car following in the CV environment. Finally, two measurements, which include time-to-collision at braking (TTCbrake) and total travel time (TTT), were employed to evaluate the effectiveness of the proposed control strategy. The results demonstrated that the VSL control played an important role in reducing rear-end crash risk and the effects of the VSL control could be affected by compliance rates. In addition, it was found that the CV environment could further enhance the safety benefits of VSL control and improve the traffic efficiency.

中文翻译：

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结合联网车辆和可变限速策略，降低雾天追尾风险

摘要 雾是一种降低行车场景能见度的天气状况，而高速公路上的瓶颈可能会导致交通缓慢。当车辆接近慢速交通时，这种现象可能会导致更高的追尾事故风险，因为司机可能无法及时观察到前方的速度降低，能见度降低，并且没有足够的时间做出反应。本研究旨在开发一种可变限速 (VSL) 控制策略，以降低雾天条件下高速公路瓶颈处的追尾事故风险。考虑到间隙和可见距离之间的不同关系，开发了VSL控制算法。VSL 策略也在完全连接的车辆 (CV) 环境中进行了测试。开发了一个反馈控制框架来结合 VSL 和 CV 控制。通过微观仿真软件 VISSIM 对具有瓶颈的高速公路路段实施和测试了所提出的 VSL 策略，并采用智能驾驶员模型 (IDM) 来解决 CV 环境中的汽车跟随问题。最后，包括制动时碰撞时间 (TTCbrake) 和总行程时间 (TTT) 的两个测量被用来评估所提出的控制策略的有效性。结果表明，VSL 控制在降低追尾事故风险方面发挥了重要作用，并且 VSL 控制的效果可能会受到合规率的影响。此外，发现CV环境可以进一步增强VSL控制的安全效益并提高交通效率。