Operating Speed on a Buffer-Separated Managed Lane

Fitzpatrick, Kay; Avelar, Raul; Lindheimer, Tomás

doi:10.3141/2616-01

Cited by 3 publications

(2 citation statements)

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“…In Part I of this paper series (Wright et al, 2019), we proposed several macroscopic modeling elements for the purpose of mathematically describing a freeway equipped with a managed lane facility (a "managed lane-freeway network"). Part I discusses the road-topological considerations of modeling two parallel traffic flows, as well as mathematical descriptions for several of the complex emergent (and sometimes counteracting) phenomena that have been observed on managed lane-freeway networks, like the so-called friction (Liu et al, 2011;Fitzpatrick et al, 2017) and smoothing (Menendez and Daganzo, 2007;Cassidy et al, 2010;Jang and Cassidy, 2012) effects.…”

Section: Introductionmentioning

confidence: 99%

Macroscopic Modeling, Calibration, and Simulation of Managed Lane-Freeway Networks, Part II: Network-scale Calibration and Case Studies

Wright,

Horowitz,

Kurzhanskiy

2019

Preprint

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In Part I of this paper series, several macroscopic traffic model elements for mathematically describing freeway networks equipped with managed lane facilities were proposed. These modeling techniques seek to capture at the macroscopic the complex phenomena that occur on managed lane-freeway networks, where two parallel traffic flows interact with each other both in the physical sense (how and where cars flow between the two lane groups) and the physiological sense (how driving behaviors are changed by being adjacent to a quantitatively and qualitatively different traffic flow).The local descriptions we developed in Part I are not the only modeling complexity introduced in managed lane-freeway networks. The complex topologies mean that network-scale modeling of a freeway corridor is increased in complexity as well. The already-difficult model calibration problem for a dynamic model of a freeway becomes more complex when the freeway becomes, in effect, two interrelating flow streams. In the present paper, we present an iterative-learning-based approach to calibrating our model's physical and driver-behavioral parameters. We consider the common situation where a complex traffic model needs to be calibrated to recreate real-world baseline traffic behavior, such that counterfactuals can be generated by training purposes. Our method is used to identify traditional freeway parameters as well as the proposed parameters that describe managed lane-freeway-network-specific behaviors. We validate our model and calibration methodology with case studies of simulations of two managed lane-equipped California freeways.

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Section: Introductionmentioning

confidence: 99%

Macroscopic Modeling, Calibration, and Simulation of Managed Lane-Freeway Networks, Part II: Network-scale Calibration and Case Studies

Wright,

Horowitz,

Kurzhanskiy

2019

Preprint

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“…Buffer separation and other geometric strategies can help to preserve these benefits. Recent research has found that higher speeds are associated with wider buffers ( 2 ). The wider ML buffer separation, travel lane, or shoulder width may also positively influence safety.…”

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confidence: 99%

Safety Evaluation of Cross-Sectional Elements of Freeway Managed Lanes

Avelar

Fitzpatrick

2018

Transportation Research Record: Journal of the Transportation R

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This paper investigated the safety implications of managed-lane cross-sectional elements. The objective of the Federal Highway Administration project was to investigate the relationship between crashes and buffer-separated managed lane dimensions. The results from several previous research studies have demonstrated that reductions in freeway lane width or shoulder width are associated with more crashes. This research found that a narrower managed-lane envelope width (i.e., left shoulder, managed-lane, and buffer width combined) is also associated with more freeway crashes for crashes of all severity levels including fatal and injury. Wider envelopes are associated a reduction in total freeway crashes, of all severities, of 2.8% in Texas, and 2.0% in California, for each additional foot of envelope width. In California, wider envelopes are associated with a reduction of 4.4% in managed-lane-related crashes resulting in fatalities and injuries at all severity levels, for each additional foot of envelope width. The analysis was conducted on nonweaving managed-lane segments that included a single managed-lane separated from the general-purpose lanes with a flush buffer area. The dataset included crashes on 128.0 miles of freeway in California (all 128.0 miles with flush buffers) and 60.4 miles of freeway in Texas (41.7 miles with pylon buffers and 18.7 miles with flush buffers). The California sites included freeways with three or four general-purpose lanes, and the Texas freeways had three to five general-purpose lanes.

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Effectiveness of road safety interventions: An evidence and gap map

Goel,

Tiwari,

Varghese

et al. 2024

Campbell Systematic Reviews

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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.

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Operating Speed on a Buffer-Separated Managed Lane

Cited by 3 publications

References 5 publications

Macroscopic Modeling, Calibration, and Simulation of Managed Lane-Freeway Networks, Part II: Network-scale Calibration and Case Studies

Macroscopic Modeling, Calibration, and Simulation of Managed Lane-Freeway Networks, Part II: Network-scale Calibration and Case Studies

Safety Evaluation of Cross-Sectional Elements of Freeway Managed Lanes

Effectiveness of road safety interventions: An evidence and gap map

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