Crash Modification Functions for Passing Relief Lanes on Two-Lane Rural Roads

2020 ◽  
Vol 2674 (9) ◽  
pp. 586-592
Author(s):  
Bhagwant Persaud ◽  
Alireza Jafari Anarkooli ◽  
Shahram Almasi ◽  
Craig Lyon
Keyword(s):  
Linear Modeling ◽  
Rural Roads ◽  
Design Decisions ◽  
Actual Length ◽  
Highway Safety Manual ◽  
Reference Sections ◽  
Original Length ◽  
Traffic Volumes ◽  
Crash Modification Factors ◽  
Mcmc Simulation

Passing relief lanes on two-lane rural roads provide passing opportunities that would otherwise be scarce where there are extensive no-passing zones, high opposing traffic volumes, or both. This paper addresses the safety effects of installing a passing lane or lengthening an existing one. It stands to reason that the effect of installing a passing lane will depend on the actual length of that lane. By extension, it is also reasonable to expect that the safety effects of lengthening an existing one will depend not only on the amount of the lengthening, but also on the original length. Yet, knowledge that can be applied to estimate these two sets of effects in a design process is lacking. The crash modification factors (CMFs) in the Highway Safety Manual (HSM) and in the CMF Clearinghouse for installing a passing lane are all single-valued, of the order of 0.75. And neither source provides CMFs for lengthening an existing passing lane. This paper seeks to address these voids by developing continuous crash modification functions (CMFunctions) for both sets of design decisions using Michigan, U.S., and Ontario, Canada, crash, geometric, and traffic data for passing lane and reference sections. Generalized linear modeling and full Bayes Markov Chain Monte Carlo (FB MCMC) simulation are used to develop cross-section regression models from which crash modification functions are derived and compared. The results are consistent with those from credible before-after studies, so are recommended for implementation in practice, in particular for HSM applications.

Prediction of Design Hourly Volume on Rural Roads

2020 ◽  
pp. 036119812096556
Author(s):  
Miloš Petković ◽  
Vladan Tubić ◽  
Nemanja Stepanović
Keyword(s):  
Coefficient Of Determination ◽  
Rural Roads ◽  
The Road ◽  
Annual Average Daily Traffic ◽  
Proposed Model ◽  
Traffic Volumes ◽  
Implementation Costs ◽  
On The Road ◽  
Predicted Values ◽  
Design Hourly Volume

Design hourly volume (DHV) represents one of the most significant parameters in the procedures of developing and evaluating road designs. DHV values can be accurately and precisely calculated only on the road sections with the implemented automatic traffic counters (ATCs) which constantly monitor the traffic volume. Unfortunately, many road sections do not contain ATCs primarily because of the implementation costs. Consequently, for many years, the DHV values have been defined on the basis of occasional counting and the factors related to traffic flow variability over time. However, it has been determined that this approach has significant limitations and that the predicted values considerably deviate from the actual values. Therefore, the main objective of this paper is to develop a model which will enable DHV prediction on rural roads in cases of insufficient data. The suggested model is based on the correlation between DHVs and the parameters defining the characteristics of traffic flows, that is, the relationship between the traffic volumes on design working days and non-working days, and annual average daily traffic. The results of the conducted research indicate that the application of the proposed model enables the prediction of DHV values with a significant level of data accuracy and reliability. The coefficient of determination (R2) shows that more than 98% of the variance of the calculated DHVs was explained by the observed DHV values, while the mean error ranged from 4.86% to 7.84% depending on the number of hours for which DHV was predicted.

scholarly journals Crash Prediction Models for Horizontal Curve Segments on Two-Lane Rural Roads in Thailand

2021 ◽  
Vol 13 (16) ◽  
pp. 9011
Author(s):  
Nopadon Kronprasert ◽  
Katesirint Boontan ◽  
Patipat Kanha
Keyword(s):  
Prediction Models ◽  
Safety Performance ◽  
Horizontal Curve ◽  
Crash Frequency ◽  
Rural Roads ◽  
Crash Prediction ◽  
Road Crashes ◽  
Highway Safety Manual ◽  
Safety Performance Functions ◽  
Crash Prediction Models

The number of road crashes continues to rise significantly in Thailand. Curve segments on two-lane rural roads are among the most hazardous locations which lead to road crashes and tremendous economic losses; therefore, a detailed examination of its risk is required. This study aims to develop crash prediction models using Safety Performance Functions (SPFs) as a tool to identify the relationship among road alignment, road geometric and traffic conditions, and crash frequency for two-lane rural horizontal curve segments. Relevant data associated with 86,599 curve segments on two-lane rural road networks in Thailand were collected including road alignment data from a GPS vehicle tracking technology, road attribute data from rural road asset databases, and historical crash data from crash reports. Safety Performance Functions (SPFs) for horizontal curve segments were developed, using Poisson regression, negative binomial regression, and calibrated Highway Safety Manual models. The results showed that the most significant parameter affecting crash frequency is lane width, followed by curve length, traffic volume, curve radius, and types of curves (i.e., circular curves, compound curves, reverse curves, and broken-back curves). Comparing among crash prediction models developed, the calibrated Highway Safety Manual SPF outperforms the others in prediction accuracy.

scholarly journals Using Recycled Aggregates from Construction and Demolition Waste in Unbound Layers of Pavements

2020 ◽  
Vol 12 (22) ◽  
pp. 9386
Author(s):  
Sajjad Pourkhorshidi ◽  
Cesare Sangiorgi ◽  
Daniele Torreggiani ◽  
Patrizia Tassinari
Keyword(s):  
Construction And Demolition Waste ◽  
Recycled Aggregates ◽  
Demolition Waste ◽  
Rural Roads ◽  
Recycled Materials ◽  
Natural Resource Conservation ◽  
Traffic Loads ◽  
Harmful Emissions ◽  
Traffic Volumes ◽  
Pavement Construction

Pavements are an expensive part of transportation infrastructures, as their construction and maintenance require large amounts of resources and materials every year and all over the world. A sustainable solution for considering environmental concerns about roads and pavements, in general, is utilizing recycled materials for their construction. This has been shown to lower the carbon footprint of the construction sector and to result in natural resource conservation, in reduction of harmful emissions and in minimization of overall costs for pavement construction and maintenance. One of the main groups of recycled materials which has attracted much attention since the end of the last century is construction and demolition waste aggregates (CDW). This paper reviews the completed studies referring to the use of the construction and demolition waste aggregates in unbound layers of pavements and compare the in-hand results from various engineering assessments of these aggregates and mixes. A number of tests and evaluations are applied in order to enhance the required quality and durability of the pavements under given traffic volumes traffic loads and climate actions. Today, unbound recycled aggregates (RA) are mainly used in the lower layers, such as subgrade, capping, sub-base and base, but in rural roads they can be adopted also for bound layers, towards the surface of the structure and may be constituents of bound layers and of novel surfacing applications.

Developing Crash Modification Factors for Horizontal Curves on Rural Two-Lane Undivided Highways Using a Cross-Sectional Study

2017 ◽  
Vol 2636 (1) ◽  
pp. 53-61 ◽  
Author(s):  
Lingtao Wu ◽  
Dominique Lord ◽  
Srinivas Reddy Geedipally
Keyword(s):  
Regression Models ◽  
Cross Sectional Study ◽  
Highway Safety ◽  
Sectional Study ◽  
Cross Sectional ◽  
Highway Safety Manual ◽  
Horizontal Curves ◽  
Before And After ◽  
Crash Modification Factors ◽  
Curve Radius

Horizontal curves have been identified as experiencing more crashes than tangent sections on roadways, especially on rural two-lane highways. The first edition of the Highway Safety Manual provides crash modification functions (CM functions) for curves on rural two-lane highways. The CM functions proposed in the manual may suffer from both outdated data and analysis technique. Before-and-after studies are usually the preferred method for estimating the safety effects of treatments. Unfortunately, this method is not feasible for curves. Previous studies have frequently used regression models for developing CM functions for horizontal curves. As recently documented in the literature, some potential problems exist with using regression models to develop crash modification factors. This research utilized a cross-sectional study to develop curvature CM functions. Curves located on Texas rural two-lane undivided highways were divided into a number of bins based on the curve radius. Safety was predicted with the assumption that these curves had been tangents. The observed number of crashes that occurred on the curves was compared with the dummy tangents and for different bins. The results showed that the horizontal curve radius has a significant role in the risk of a crash. From these results, a new CM function was developed. The prediction performance of the Highway Safety Manual CM function was compared with the new CM function in this study and another function that was recently proposed in the literature. It was found that the new CM function documented in this study outperformed both.

Some Limitations of the Models in the Highway Safety Manual to Predict Run-off-Road Crashes

2013 ◽  
Vol 2377 (1) ◽  
pp. 38-48
Author(s):  
Shaw-Pin Miaou
Keyword(s):  
Prediction Models ◽  
Highway Safety ◽  
Roadside Safety ◽  
Highway Safety Manual ◽  
Run Off ◽  
Section Design ◽  
Single Vehicle ◽  
Crash Modification Factors ◽  
Model Equations ◽  
Crash Prediction Models

Crash-prediction models in the current edition of the Highway Safety Manual (HSM) have been developed to predict crash frequency by collision type and severity level for specific types of roadways and sites. Each model is made up of three major components: safety performance functions (SPFs), crash modification factors, and calibration factors. The objective of this study was to identify the limitations of the prediction models in estimating single-vehicle, run-off-road (SVROR) crashes for roadside safety analyses and suggest needed changes and developments. The paper presents a review of the state of the models in HSM and focuses on SPFs. Data from FHWA's safety effects of cross-section design for two-lane roads database were used to gain insight about the characteristics of SVROR crashes and total crashes, and to identify the limitations of the current models in predicting the frequency, type, and severity of SVROR crashes. Three major areas of limitations of SPFs are discussed: (a) assumptions involved in development, (b) variables that are potentially important to roadside design but not considered, and (c) statistical bias and uncertainty of the model equations.

scholarly journals Evaluating the Safety Impacts of Increased Speed Limits on Freeways in Kansas Using Before-And-After Study Approach

2018 ◽  
Vol 11 (1) ◽  
pp. 119 ◽  
Author(s):  
Reza Shirazinejad ◽  
Sunanda Dissanayake ◽  
Ahmed Al-Bayati ◽  
David York
Keyword(s):  
Traffic Safety ◽  
Economic Benefits ◽  
Group Method ◽  
Speed Limit ◽  
Speed Limits ◽  
Study Approach ◽  
Highway Safety Manual ◽  
Before And After ◽  
Crash Modification Factors ◽  
Before And After Study

In the summer of 2011, a change in the Kansas laws came into effect, increasing the speed limit on a selected set of freeway sections from 70 mph to 75 mph. Higher speeds were thought to have economic benefits, mostly because the travel time reduction means people reach their destinations more quickly. In this study, the sections where the speed limits remained unchanged, are compared to freeway sections that have been influenced by speed limit increase, to evaluate safety effectiveness. The study utilizes the before-and-after study with comparison group method to assess the safety effects provided in the Highway Safety Manual (HSM). Two crash datasets, obtained by considering three years before and three years after the speed limit increase, were compared in order to evaluate the safety effects of the speed limit change. The crash modification factors (CMFs) were estimated, which showed that there was a 27% increase in total crashes and a 35% increase in fatal and injury crashes across all sections after the speed limit change, and these increases were statistically significant at 95% confidence level. These confounding results show that the speed limit increase has not been beneficial for traffic safety in Kansas, and hence it is important to be cautious in such future situations. Also, additional data have been presented which would be beneficial in identifying and understanding any behavior change in drivers following a speed limit increase.

Alternative Approach for Combining Multiple Crash Modification Factors Using Adjustment Function and Analytic Hierarchy Process

2017 ◽  
Vol 2636 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Juneyoung Park ◽  
Mohamed A. Abdel-Aty
Keyword(s):  
Specific Method ◽  
Improve Performance ◽  
Analytic Hierarchy ◽  
Highway Safety Manual ◽  
Alternative Approach ◽  
Critical Issues ◽  
Crash Modification Factors ◽  
Multiple Treatments ◽  
Hierarchy Process ◽  
Combining Methods

The safety effects of multiple treatments have recently emerged as an important issue of validation for the Highway Safety Manual procedures to improve performance of the predictive process. To estimate the combined safety effects of multiple crash modification factors (CMFs) more reliably, several combining approaches have been suggested. However, several critical issues still exist for the combining methods, such as overestimation, region-specific method, and a nonscientific approach. Therefore, this study suggests a novel adjustment method to combine multiple CMFs and to enhance the reliability of combining the safety effects of multiple treatments. Various combinations of CMFs for single and multiple treatments were estimated or obtained from previous studies and used for an exploratory analysis. Moreover, an alternative combining approach with the development of an adjustment function was suggested through comparison with the existing combining methods by using a multicriterion decision-making process. The results show that the proposed alternative combining method provides better estimates than the existing methods and can account for different roadway types and severity levels. Thus, it can be recommended that the safety effects of multiple treatments be estimated with the proposed new combining approach to overcome the overestimation issue and produce results that are more reliable.

scholarly journals Safety performance functions in Dedicated Bus Lane of BRT on Caracas Avenue Corridor at Bogotá city

Inge CUC ◽  
2019 ◽  
Vol 15 (2) ◽  
pp. 66-77
Author(s):  
Kelly Andrea Rodríguez Polo ◽  
Santiago Henao Pérez
Keyword(s):  
Traffic Accidents ◽  
Negative Binomial ◽  
Central Line ◽  
Safety Performance ◽  
Transport Systems ◽  
Accident Prediction ◽  
Highway Safety Manual ◽  
Safety Performance Functions ◽  
Traffic Volumes ◽  
Bus Lane

Introduction- Road safety is a global concern due to the fact that traffic accidents represent serious temporary and / or permanent damage to the health of those involved. On the other hand, the Bus Rapid Transit (BRT) systems carries a large volume of passengers and during their operation; they are involved in this problem. Objective- Accident prediction model implemented in the Highway Safety Manual 2010 or HSM is an alternative to evaluate the strategies that allow to reduce accidents in this type of systems. However, there is not specified safety performance functions (SPFs) developed for BRT systems. In the present work, the accident model of HSM is adapted by calibration of general SPFs expressions of the manual and also, SPFs were developed for BRTs installed on the central-line of main roads and use an exclusive lane of all other transport systems (both public or private) and mobility (e.g. bike paths). Method / Results - Crashes reports and traffic volumes data supplied by the Department of Transportation of Bogotá were used. The model was calibrated using the safety performance functions (SPFs) of the HSM and a specific developed functions for the BRT conditions. These SPFs were developed using a negative binomial model in roadway segments and intersections. Conclusions- Through the validation, it was found that the functions developed have a better fit than the established SPF of the HSM. The developed SPFs can be used as a tool to define safety performance guidelines of Bogotá's BRT corridors in the coming years.

Sign in / Sign up

Export Citation Format

Share Document