Safety Performance of Crossroad Ramp Terminals at Single-Point and Tight Diamond Interchanges

2021 ◽  
pp. 036119812110299
Author(s):  
Darren J. Torbic ◽  
Richard J. Porter ◽  
Jeff Gooch ◽  
Kristin Kersavage
Keyword(s):  
Urban Areas ◽  
Prediction Models ◽  
Single Point ◽  
Highway Safety ◽  
Safety Performance ◽  
Crash Prediction ◽  
Highway Safety Manual ◽  
Predictive Methods ◽  
Diamond Interchanges ◽  
Crash Prediction Models

Single-point diamond interchanges and tight diamond interchanges are two alternative interchange types that are considered in urban areas where right-of-way is usually limited. The Highway Safety Manual First Edition predictive methods for freeways and interchanges are capable of estimating the safety performance of freeway mainline, freeway-ramp terminal, and ramp proper segments associated with these interchange types. However, limited research has been conducted to predict and compare the safety performance of the crossroad ramp terminals for these two alternative interchange designs, as would be necessary for a performance-based approach to interchange alternatives analysis. Planners, designers, and safety managers would benefit from having tools to compare the safety performance of these crossroad ramp terminals to make more informed decisions about their use and application in the urban environment. Research was undertaken with the objective of developing new intersection crash prediction models for crossroad ramp terminals at single-point diamond interchanges and crossroad ramp terminals at tight diamond interchanges. In general, it was found that the crash prediction models for crossroad ramp terminals at single-point diamond interchanges predicted more crashes than the models for crossroad ramp terminals at tight diamond interchanges in higher volume conditions. The differences were primarily driven by the property-damage-only crash predictions. Comparisons of the crash prediction models suggested that the two sets of models appear compatible and provide reasonable results over the range of applicable traffic volume conditions.

New Intersection Crash Prediction Models for the Second Edition of the Highway Safety Manual

2021 ◽  
pp. 036119812110398
Author(s):  
Darren J. Torbic ◽  
Daniel Cook ◽  
Joseph Grotheer ◽  
Richard Porter ◽  
Jeffrey Gooch ◽  
...  
Keyword(s):  
Traffic Control ◽  
Prediction Models ◽  
Highway Safety ◽  
Crash Severity ◽  
Crash Prediction ◽  
Part C ◽  
Highway Safety Manual ◽  
Rural And Urban ◽  
Diamond Interchanges ◽  
Crash Prediction Models

The objective of this research was to develop new intersection crash prediction models for consideration in the second edition of the Highway Safety Manual (HSM), consistent with existing methods in HSM Part C and comprehensive in their ability to address a wide range of intersection configurations and traffic control types in rural and urban areas. The focus of the research was on developing safety performance functions (SPFs) for intersection configurations and traffic control types not currently addressed in HSM Part C. SPFs were developed for the following general intersection configurations and traffic control types: rural and urban all-way stop-controlled intersections; rural three-leg intersections with signal control; intersections on high-speed urban and suburban arterials (i.e., arterials with speed limits greater than or equal to 50 mph); urban five-leg intersections with signal control; three-leg intersections where the through movements make turning maneuvers at the intersections; crossroad ramp terminals at single-point diamond interchanges; and crossroad ramp terminals at tight diamond interchanges. Development of severity distribution functions (SDFs) for use in combination with SPFs to estimate crash severity as a function of geometric design elements and traffic control features was explored; but owing to challenges and inconsistencies in developing and interpreting the SDFs, it was recommended for the second edition of the HSM that crash severity for the new intersection configurations and traffic control types be addressed in a manner consistent with existing methods in Chapters 10, 11, and 12 of the first edition, without use of SDFs.

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.

Calibration of the Highway Safety ManualGiven Safety Performance Functions for RuralMultilane Segments and Intersections in Kansas

2017 ◽  
Author(s):  
Syeda Rubaiyat Aziz ◽  
Sunanda Dissanayake
Keyword(s):  
Safety Evaluation ◽  
Highway Safety ◽  
Safety Performance ◽  
Regression Coefficients ◽  
Local Conditions ◽  
Crash Prediction ◽  
Highway Safety Manual ◽  
Satisfactory Level ◽  
Safety Performance Functions ◽  
Predictive Methods

The Highway Safety Manual (HSM) provides models and methodologies for safety evaluation and prediction of safety performance of various types of roadways. However, predictive methods in the HSM are of limited use if they are not calibrated for local conditions. In this study, calibration procedures given in the HSM were followed for rural segments and intersections in Kansas. Results indicated that HSM overpredicts fatal and injury crashes and underpredicts total crashes on rural multilane roadway segments in Kansas. Therefore, existing safety performance functions (SPFs) must be adjusted for Kansas conditions, in order to increase accuracy of crash prediction. This study examined a way to adjust HSM calibration procedures by development of new regression coefficients for existing HSM-given SPF. Final calibration factors obtained through modified SPFs indicated significant improvement in crash prediction for rural multilane segments in Kansas. Additionally, obtained calibration factors indicated that the HSM is capable of predicting crashes at intersections at satisfactory level.

Assessing Transferability of Highway Safety Manual Crash Prediction Models to Data from Italy

2014 ◽  
Vol 2433 (1) ◽  
pp. 129-135 ◽  
Author(s):  
Francesca Russo ◽  
Mariarosaria Busiello ◽  
Salvatore A. Biancardo ◽  
Gianluca Dell'Acqua
Keyword(s):  
Prediction Models ◽  
Highway Safety ◽  
Crash Prediction ◽  
Highway Safety Manual ◽  
Crash Prediction Models

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.

Application of Highway Safety Manual Method for Ramp Crash Prediction to Loop and Diamond Ramps

2017 ◽  
Vol 2636 (1) ◽  
pp. 43-52 ◽  
Author(s):  
Darren J. Torbic ◽  
Douglas W. Harwood ◽  
Karin M. Bauer
Keyword(s):  
Prediction Method ◽  
Highway Safety ◽  
Safety Performance ◽  
Prediction Methods ◽  
Crash Prediction ◽  
Crash Data ◽  
Manual Method ◽  
Highway Safety Manual ◽  
Separate Calibration

The AASHTO Highway Safety Manual (HSM) now includes crash prediction procedures for ramps. Research was undertaken to assess how well these new crash prediction methods represented the safety performance of two ramp types with distinctly different geometrics: loop ramps and diamond ramps. The HSM crash prediction procedures were applied to 235 loop ramps and 243 diamond ramps in two states—California and Washington—and the results were compared with 5 years of actual crash data for the same ramps. The results indicate that the HSM crash prediction method can be applied to both loop and diamond ramps, but to compare the safety performance of these two ramp types properly, separate calibration of loop and diamond ramps is needed.

A Comparative Analysis on Performance of Severe Crash Prediction Methods

2018 ◽  
Vol 2672 (30) ◽  
pp. 109-119 ◽  
Author(s):  
Raul E. Avelar ◽  
Karen Dixon ◽  
Sruthi Ashraf
Keyword(s):  
Prediction Models ◽  
Distribution Functions ◽  
Safety Performance ◽  
Future Research ◽  
Alternative Analysis ◽  
Crash Prediction ◽  
Explanatory Variables ◽  
Safety Performance Functions ◽  
Comprehensive Comparison ◽  
Crash Prediction Models

The objective of this paper is to compare the performance and tradeoffs between two alternative analysis methods for developing crash prediction models for severe crashes: a direct estimation of severe crashes using frequency models, and an indirect but popular approach of combining frequency of total crashes models and some form of severity distribution functions (SDFs). The researchers conducted a comprehensive comparison of these modeling methods to illustrate the strengths and weaknesses of each alternative, and to inform future research that intends to develop such models. An examination of the theoretical characteristics of the modeling approach is presented and discussed. The performance of the two modeling alternatives is compared using two different datasets. The results of those comparisons showed very similar performances by both techniques. Finally, a sensitivity analysis is presented to explore how the performance of these techniques vary by degree of dispersion and observed correlation levels of total and severe injury crashes (KAB; injury scale in which K = fatal [killed], A = incapacitating injury, B = nonincapacitating injury) with potential explanatory variables. The results from these analyses tended to favor the use of SDFs in combination with total crashes safety performance functions (SPFs), as the prediction tended to show reduced dispersion under most conditions. However, performance of the KAB SPF model outperformed the combination of SDF and SPF for total crashes when KAB and non-KAB crashes had a common predictor but with effects in opposite directions.

Sign in / Sign up

Export Citation Format

Share Document