Four-Regime Speed–Flow Relationships for Work Zones with Police Patrol and Automated Speed Enforcement

Avrenli, Kivanc A; Benekohal, Rahim F.; Ramezani, Hamidreza

doi:10.3141/2272-05

Cited by 4 publications

(3 citation statements)

References 19 publications

(17 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There are three stages (free flow, transition and congestion) to describe the traffic flow [16]. In free flow stage, there is a low traffic density and the traffic will flow stably.…”

Section: Disturbancementioning

confidence: 99%

Optimal Variable Speed Limit Control under Connected Work Zone and Connected Vehicle Environment

Du¹,

Razavi²,

Genders³

2017

Proceedings of the International Symposium on Automation and Robotics in Construction (IAARC)

View full text Add to dashboard Cite

Despite the long-term benefits gained through road maintenance projects, the work zone involved can cause serious traffic congestion and greatly increase traffic delay. Variable speed limit (VSL) enforcement provides a means to reduce the travel time and alleviate the traffic congestion in work zones. This paper presents a novel proactive VSL control algorithm for freeway work zone traffic management under connected work zone and connected vehicle environment. In a connected work zone environment, the estimated work zone capacity can be easily shared considering the work zone configuration factors such as number of lane closure, signal distance, presence of work activity, etc. After incorporating the estimated capacity which contributes to a better modeling of the traffic disturbance caused by work zone, the traffic flow predictive model was established to obtain preventive measures and avoid traffic breakdown. In addition, based on the trajectories of individual vehicles recorded and shared by connected vehicles, the objective function was developed for the VSL control algorithm to minimize the Total Travel Time which can be used to measure level of the traffic congestion. The VSL control was implemented and tested in a traffic simulator SUMO. The results showed that the designed VSL algorithm effectively decreased the total travel time with the reduction of the speed variance which potentially improved the traffic safety at work zones.

show abstract

“…There are three stages (free flow, transition and congestion) to describe the traffic flow [16]. In free flow stage, there is a low traffic density and the traffic will flow stably.…”

Section: Disturbancementioning

confidence: 99%

Optimal Variable Speed Limit Control under Connected Work Zone and Connected Vehicle Environment

Du¹,

Razavi²,

Genders³

2017

Proceedings of the International Symposium on Automation and Robotics in Construction (IAARC)

View full text Add to dashboard Cite

show abstract

“…The traffic flow rate within bottleneck area shows a slight reduction when a queue forms upstream, namely the capacity drop, while a speed reduction line appears when the queue discharges. Multi-part piecewise curves, more commonly seen in empirical studies, usually result in better estimation accuracy [12][13][14]. However, in the authors' view, with sufficient sample points, multiple piecewise curves would outperform their single-or two-piece counterparts on goodness of fit, but setting too many traffic regimes could weaken transferability of the estimated model.…”

Section: Introductionmentioning

confidence: 99%

“…Field traffic data was applied to determine the influence of merging vehicles on lane speed-flow relationships of work zone traffic. As one of the fundamental diagrams, the speed-flow diagram is often used to evaluate work-zone traffic conditions at the macroscopic level [1,12,14,18,19], so it was also applied in the current study. Variance of lane utilizations at multiple locations was used to identify spatial distribution of merging behaviors along work zones.…”

Section: Introductionmentioning

confidence: 99%

Merging Vehicles and Lane Speed-Flow Relationship in a Work Zone

Zhang

2018

Sustainability

View full text Add to dashboard Cite

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.

show abstract

Effectiveness of road safety interventions: An evidence and gap map

Goel,

Tiwari,

Varghese

et al. 2024

Campbell Systematic Reviews

View full text Add to dashboard Cite

BackgroundRoad Traffic injuries (RTI) are among the top ten leading causes of death in the world resulting in 1.35 million deaths every year, about 93% of which occur in low‐ and middle‐income countries (LMICs). Despite several global resolutions to reduce traffic injuries, they have continued to grow in many countries. Many high‐income countries have successfully reduced RTI by using a public health approach and implementing evidence‐based interventions. As many LMICs develop their highway infrastructure, adopting a similar scientific approach towards road safety is crucial. The evidence also needs to be evaluated to assess external validity because measures that have worked in high‐income countries may not translate equally well to other contexts. An evidence gap map for RTI is the first step towards understanding what evidence is available, from where, and the key gaps in knowledge.ObjectivesThe objective of this evidence gap map (EGM) is to identify existing evidence from all effectiveness studies and systematic reviews related to road safety interventions. In addition, the EGM identifies gaps in evidence where new primary studies and systematic reviews could add value. This will help direct future research and discussions based on systematic evidence towards the approaches and interventions which are most effective in the road safety sector. This could enable the generation of evidence for informing policy at global, regional or national levels.Search MethodsThe EGM includes systematic reviews and impact evaluations assessing the effect of interventions for RTI reported in academic databases, organization websites, and grey literature sources. The studies were searched up to December 2019.Selection CriteriaThe interventions were divided into five broad categories: (a) human factors (e.g., enforcement or road user education), (b) road design, infrastructure and traffic control, (c) legal and institutional framework, (d) post‐crash pre‐hospital care, and (e) vehicle factors (except car design for occupant protection) and protective devices. Included studies reported two primary outcomes: fatal crashes and non‐fatal injury crashes; and four intermediate outcomes: change in use of seat belts, change in use of helmets, change in speed, and change in alcohol/drug use. Studies were excluded if they did not report injury or fatality as one of the outcomes.Data Collection and AnalysisThe EGM is presented in the form of a matrix with two primary dimensions: interventions (rows) and outcomes (columns). Additional dimensions are country income groups, region, quality level for systematic reviews, type of study design used (e.g., case‐control), type of road user studied (e.g., pedestrian, cyclists), age groups, and road type. The EGM is available online where the matrix of interventions and outcomes can be filtered by one or more dimensions. The webpage includes a bibliography of the selected studies and titles and abstracts available for preview. Quality appraisal for systematic reviews was conducted using a critical appraisal tool for systematic reviews, AMSTAR 2.Main ResultsThe EGM identified 1859 studies of which 322 were systematic reviews, 7 were protocol studies and 1530 were impact evaluations. Some studies included more than one intervention, outcome, study method, or study region. The studies were distributed among intervention categories as: human factors (n = 771), road design, infrastructure and traffic control (n = 661), legal and institutional framework (n = 424), post‐crash pre‐hospital care (n = 118) and vehicle factors and protective devices (n = 111). Fatal crashes as outcomes were reported in 1414 records and non‐fatal injury crashes in 1252 records. Among the four intermediate outcomes, speed was most commonly reported (n = 298) followed by alcohol (n = 206), use of seatbelts (n = 167), and use of helmets (n = 66). Ninety‐six percent of the studies were reported from high‐income countries (HIC), 4.5% from upper‐middle‐income countries, and only 1.4% from lower‐middle and low‐income countries. There were 25 systematic reviews of high quality, 4 of moderate quality, and 293 of low quality.Authors' ConclusionsThe EGM shows that the distribution of available road safety evidence is skewed across the world. A vast majority of the literature is from HICs. In contrast, only a small fraction of the literature reports on the many LMICs that are fast expanding their road infrastructure, experiencing rapid changes in traffic patterns, and witnessing growth in road injuries. This bias in literature explains why many interventions that are of high importance in the context of LMICs remain poorly studied. Besides, many interventions that have been tested only in HICs may not work equally effectively in LMICs. Another important finding was that a large majority of systematic reviews are of low quality. The scarcity of evidence on many important interventions and lack of good quality evidence‐synthesis have significant implications for future road safety research and practice in LMICs. The EGM presented here will help identify priority areas for researchers, while directing practitioners and policy makers towards proven interventions.

show abstract

Four-Regime Speed–Flow Relationships for Work Zones with Police Patrol and Automated Speed Enforcement

Cited by 4 publications

References 19 publications

Optimal Variable Speed Limit Control under Connected Work Zone and Connected Vehicle Environment

Optimal Variable Speed Limit Control under Connected Work Zone and Connected Vehicle Environment

Merging Vehicles and Lane Speed-Flow Relationship in a Work Zone

Effectiveness of road safety interventions: An evidence and gap map

Contact Info

Product

Resources

About