Abstract
In addition to closed merge lanes as physical bottlenecks of work zones, traffic oscillations caused by merging vehicles at multiple locations could reduce work-zone capacity. This study took a step-wise procedure to reveal spatial distributions of merging vehicles along work zones and their influence on speed-flow relationships of lane traffic flows. Field data showed that inserting vehicles from merge lanes could spread their influence over adjacent unclosed through lanes. Moreover, with increases in total volume, merging vehicles could choose their inserting positions further upstream of the work zone, which could induce oscillations near the insertion point. At the identified upstream bottlenecks, capacity drop was found in speed-flow diagrams of through-lane traffic, but it was not found in the diagrams of merge-lane traffic flows. Lack of sufficient demand and special merging behaviors on merge lanes could be attributed to the distinct speed-flow relationship. Two-part piecewise regression models were developed to fit the speed-flow relationships of uncongested and congested flows of through lanes. By comparing the estimated speed-flow models, it was found that when a queue is forming, the extent of the capacity drop and speed reduction is different for through lanes. Queue discharge uses different lengths of time on through lanes and multiple merging locations.
Highlights
As transportation infrastructure ages, work zones are frequently established on highways for pavement rehabilitation and facility repair, causing traffic congestion in the work-zone segment
Lane traffic flow was deduced from these videos, and lane speed was collected by a radar velometer at each site
Obvious capacity drop can be seen in these diagrams, which means that the traffic oscillations caused by merging vehicles exist in both the median lane and inside lane
Summary
Work zones are frequently established on highways for pavement rehabilitation and facility repair, causing traffic congestion in the work-zone segment. In real traffic, merging vehicles could emerge at more locations upstream of the work zone, so their disturbances on through-lane traffic could be more frequent, making the oscillation patterns more complex In this view, it is necessary to collect traffic data at various work-zone sites, rather than at single sites, as most studies are currently done. Variance of lane utilizations at multiple locations was used to identify spatial distribution of merging behaviors along work zones Based on this knowledge, the study sites where merging behaviors frequently occur can be identified, and traffic data collected at these sites were applied to model lane speed-flow relationships. The knowledge obtained from this paper is expected to be a reference for work-zone control plan design and control device deployment, such as dynamic merging control, speed limit signs, and deceleration rumble strips
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
