Abstract
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.
Highlights
Unclear weather conditions and incidents are common factors that impact traffic speed
To apply the proposed model, speed data corresponding to each traffic message channel (TMC) was divided by the posted limit speed at that TMC
We fitted the mixture of two linear regressions using this data. e model will be useful to describe the change of the mean of the speed distribution of the congested regime, as the first component, and free-flow regime, as the second component, as a function of the precipitation level and the percentage of lane closure
Summary
Unclear weather conditions and incidents are common factors that impact traffic speed. With the increase in travel demand and number of vehicles, congestion has amplified impairing the efficiency of the road network, especially highways. To alleviate this consequence, developing novel Intelligent Transportation System (ITS) technologies and reforming policies for traffic management and operations has become substantial. By the same token, quantifying the extent of weather conditions and incidents on traffic stream speeds is a key in effective and real-time traffic management and operation. Weather is an important factor that impacts traffic stream speeds, and causes 15% of all nonrecurring congestion in the United States [10]. Novel traffic management strategies to mitigate the effect of traffic incidents are essential to incident management agencies around the world
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