Unpredictable and heterogeneous weather conditions and road incidents are common factors that impact highway traffic speeds. A better understanding of the interplay of different factors that affect roadway traffic speeds is essential for policymakers to mitigate congestion and improve road safety. This study investigates the effect of precipitation and incidents on the speed of traffic in the eastbound direction of I-64 in Virginia. To the best of our knowledge, this is the first study that studies the relationship between precipitation and incidents as factors that would have a combined effect on traffic stream speeds. Furthermore, using a mixture model of two linear regressions, we were able to model the two different regimes that the traffic speed could be classified into, namely, free-flow and congested. Using INRIX traffic data from 2013 through 2016 along a 25.6-mi section of Interstate 64 in Virginia, results show that the reduction of traffic speed only due to incidents ranges from 41% to 75% if the road is already congested. In this case, precipitation was found to be statistically insignificant. However, regardless of the incident impact, the effect of light rain in free-flow conditions ranges from insignificant to a 4% speed reduction while the effect of heavy rain ranges from a 0.6% to a 6.5% speed reduction when the incident severity is low but has a roughly double effect when the incident severity is high.

中文翻译：

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降雨和突发事件对交通流速度的共同影响

不可预测的，异质的天气状况和道路事故是影响高速公路交通速度的常见因素。更好地了解影响道路交通速度的不同因素之间的相互作用对于决策者减轻拥堵和改善道路安全至关重要。这项研究调查了降雨和事件对弗吉尼亚州I-64东行方向交通速度的影响。据我们所知，这是第一项研究降水和突发事件之间关系的因素，这是对交通流速度产生综合影响的因素。此外，使用两个线性回归的混合模型，我们能够对交通速度可以分为自由流动和拥堵的两种不同模式进行建模。使用2013年至2016年的INRIX交通数据以及弗吉尼亚州州际64号州际公路25.6英里的部分，结果显示，如果道路已经拥堵，仅由于事故而导致的交通速度降低幅度为41％至75％。在这种情况下，发现降水量在统计上不重要。但是，不管事件的影响如何，在自由流动条件下，小雨的影响范围从微不足道的降低到4％，而当事件的严重程度较低时，大雨的影响范围从0.6％到6.5％的降低范围。但在事件严重性较高时，具有大致双重效果。发现降水在统计上不重要。但是，不管事件的影响如何，在自由流动条件下，小雨的影响范围从微不足道的降低到4％，而当事件的严重程度较低时，大雨的影响范围从0.6％到6.5％的降低范围。但在事件严重性较高时，具有大致双重效果。发现降水在统计上不重要。但是，不管事件的影响如何，在自由流动条件下，小雨的影响范围从微不足道的降低到4％，而当事件的严重程度较低时，大雨的影响范围从0.6％到6.5％的降低范围。但在事件严重性较高时，具有大致双重效果。