Development of safety performance functions and crash modification factors for expressway ramps

Choi, Yosoon; Park, Sung Ho; Ko, Han-Geom; Kim, Kyung Hyun; Yun, Ilsoo

doi:10.1007/s12205-017-0582-1

Cited by 9 publications

(10 citation statements)

References 7 publications

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“…Lastly, for the third situation, at 0 X = , the entrance ramp in front of it has little impact on the pressure potential The separation of variable technique is applied to solve the solution of the initial-boundary value problem (IBVP) in (5). However, in this paper, we do not attach specific derivation because we want to focus on the objectives of our paper.…”

Section: Research Design and Approachmentioning

confidence: 99%

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The Behavior of the Instantaneous Speed Ratio at Merging Area of Traffic Flowing on Federal Highway

Basri¹,

Mohamed²,

Adnan³

et al. 2021

cea

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The purposes of this study are to determine the ratio of instantaneous speed on Federal highway at Kilometer 32.9 from Kuala Lumpur to Shah Alam, to analyse the implications of the instantaneous speed ratio's numerical findings, and to examine the behaviour of convergence for each level of easiness to flow. The continuous flow model is one of the traffic flow theories that conclude the traffic flow is identical to the equation of heat. The research design used in this study is a comparative model. The continuous flow model uses a boundary value problem as well as additional constraints to solve the differential equation solution. The videotaping approach was used to select a sample of highway traffic data on the tapered acceleration path. The findings of this study disclosed that the ratio of instantaneous speed converged slower at lower levels of easiness to flow than at higher levels of easiness to flow. The ratio of instantaneous speed was found to be more accurate when the additional iteration numbers were considered and the traffic's instantaneous speed ratio on the Federal highway at Kilometer 32.9 from Kuala Lumpur to Shah Alam was less than 1.39 at location 0.4 of 1. That value is less than 1.4 as proposed by the theoretical model. In conclusion, the mathematical model was found to be accurate in estimating the safe distance and speed of vehicles on merging area so that the collision can be minimized and for the assessment and decision-making of the configuration of the traffic flow. As the implication, this study offers the potential to increase the efficiency of the traffic flowing through the entrance ramp.

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Section: Research Design and Approachmentioning

confidence: 99%

“…However, some studies on the entrance ramp design concentrate on the development of the entrance ramp rather than evaluating the existing entrance ramp. This covers study by [1], [2], [3], [4], [5] and [6]. Therefore, it is considerable for us to widen the discussion regarding the configuration of the entrance ramp in Malaysia.…”

Section: Introductionmentioning

confidence: 99%

The Behavior of the Instantaneous Speed Ratio at Merging Area of Traffic Flowing on Federal Highway

Basri¹,

Mohamed²,

Adnan³

et al. 2021

cea

View full text Add to dashboard Cite

show abstract

“…The popular and well-known method for estimating the parameters of GMM is the maximum likelihood estimation (MLE). To train samples TTC i , the MLE function of GMM can be written as Equation (5).…”

Section: Ttcs' Distribution Prediction With Gmmmentioning

confidence: 99%

“…It is found that ramp AADT, the number of exit ramp lanes, ramp alignment [5], speed-changing lane length [6][7][8], vehicle characteristics (steering, acceleration, and speed) [9,10], the number of lanes of ramps [11,12], driving behaviors [13,14], etc., are closely related to ramp crashes.…”

Section: Introductionmentioning

confidence: 99%

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Crash Risk Assessment of Off-Ramps, Based on the Gaussian Mixture Model Using Video Trajectories

Hao

Cui

et al. 2020

Sustainability

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The focus of this paper is the crash risk assessment of off-ramps in Xi’an. The time-to-collision (TTC) is used for the measurement and cross-comparison of the crash risk of each location. Five sites from the urban expressway in Xi’an were selected to explore the TTC distribution. An unmanned aerial vehicle and a camera were used to collect traffic flow data for 20 min at each site. The parameters, including speed, deceleration rate, truck percentage, traffic volume, and vehicle trajectories, were extracted from video images. The TTCs were calculated for each vehicle. The Gaussian mixture model (GMM) was proposed to predict the TTC probability density functions (PDFs) and cumulative density functions (CDFs) for five sites. The Kolmogorov–Smirnov (K-S) test indicated that the samples followed the estimated GMM distribution. The relationship between the crash risk level and influencing factors was studied by an ordinal logistic regression model and a naive Bayesian model. The results showed that the naive Bayesian model had an accuracy of 86.71%, while the ordinal logistic regression model had an accuracy of 84.81%. The naive Bayesian model outperformed the ordinal logistic regression model, and it could be applied to the real-time collision warning system.

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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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Development of safety performance functions and crash modification factors for expressway ramps

Cited by 9 publications

References 7 publications

The Behavior of the Instantaneous Speed Ratio at Merging Area of Traffic Flowing on Federal Highway

The Behavior of the Instantaneous Speed Ratio at Merging Area of Traffic Flowing on Federal Highway

Crash Risk Assessment of Off-Ramps, Based on the Gaussian Mixture Model Using Video Trajectories

Effectiveness of road safety interventions: An evidence and gap map

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