Appraisal of the Interactive Highway Safety Design Model’s Crash Prediction and Design Consistency Modules: Case Studies from Pennsylvania

2009 ◽  
Vol 135 (2) ◽  
pp. 62-73 ◽  
Author(s):  
Eric T. Donnell ◽  
Francis Gross ◽  
Brandon P. Stodart ◽  
Kenneth S. Opiela
Keyword(s):  
Case Studies ◽  
Highway Safety ◽  
Crash Prediction ◽  
Safety Design ◽  
Design Consistency

Speed-Profile Model for Two-Lane Rural Highways

2000 ◽  
Vol 1737 (1) ◽  
pp. 42-49 ◽  
Author(s):  
Kay Fitzpatrick ◽  
Jon M. Collins
Keyword(s):  
Highway Safety ◽  
Geometric Features ◽  
Speed Profile ◽  
Model Design ◽  
Rural Highways ◽  
Profile Model ◽  
Safety Design ◽  
Acceleration And Deceleration ◽  
Speed Prediction ◽  
Design Consistency

Design consistency refers to highway geometry’s conformance with driver expectancy. Generally, drivers make fewer errors at geometric features that conform with their expectations. A proposed method for evaluating design consistency is to predict the speed along an alignment by using a speed-profile model. A speed-profile model was developed by using the following: speed prediction equations that calculate the expected speed at horizontal, vertical, or combination curves; assumed desired speed for the roadway; TWOPAS equations that determine the performance-limited speeds at every point; acceleration and deceleration rates; and several documented assumptions. The speed-profile model can be used to evaluate the design consistency of a facility or to generate a speed profile along an alignment. In conclusion, the speed-profile model developed appears to provide a suitable basis for the Interactive Highway Safety Design Model design consistency module.

Improved speed-profile model for two-lane rural highways

2003 ◽  
Vol 30 (6) ◽  
pp. 1055-1065 ◽  
Author(s):  
Said M Easa
Keyword(s):  
Highway Safety ◽  
Extended Model ◽  
Speed Profile ◽  
Rural Highways ◽  
Profile Model ◽  
Horizontal Curves ◽  
Sight Distance ◽  
Safety Design ◽  
Speed Change ◽  
Design Consistency

The speed-profile model has been suggested as a valuable tool for evaluating geometric design consistency for two-lane rural highways with isolated and combined horizontal and vertical alignments. The model determines the operating speeds on the speed-change (SC) segment, which is the distance between speed-limiting curves. The speed-limiting curves are the horizontal curves and the limited sight-distance crest vertical curves on horizontal tangents, where the sight distance required by the design guides is not satisfied. The model assumes that deceleration begins where required, which implies that the next curve is visible when deceleration starts. This paper presents an extension to the speed-profile model to incorporate the effect of sight obstruction on operating speeds and deceleration rates. The SC segment may include nonlimited sight–distance crest vertical and sag vertical curves. These curves may present sight obstruction. A procedure to determine whether the sight line is obstructed is developed. If it does, simple formulas are applied for revising the operating-speed profile. The extended model is suitable for inclusion in the design consistency module of the interactive highway safety design model.Key words: speed profile, model, two-lane highways, alignments, design consistency.

Interactive Highway Safety Design Model: Issues Related to Driver Modeling

1998 ◽  
Vol 1631 (1) ◽  
pp. 20-27 ◽  
Author(s):  
William H. Levison
Keyword(s):  
Decision Processes ◽  
Highway Safety ◽  
Design Model ◽  
Accident Analysis ◽  
Policy Review ◽  
Federal Highway ◽  
Safety Design ◽  
Design Consistency ◽  
And Control ◽  
Geometric Designs

The Federal Highway Administration has undertaken a multiyear project to develop the Interactive Highway Safety Design Model (IHSDM), which is a set of software tools to analyze candidate highway geometric designs from a safety standpoint. The IHSDM is envisioned to contain five analysis tools or “modules”: (1) policy review, (2) design consistency, (3) accident analysis, (4) traffic analysis, and (5) driver/vehicle analysis. The structure of the driver/vehicle module is reviewed, with emphasis on the driver component. Modeling issues regarding decision and control are discussed. Major issues include (1) perceptual and decision processes in planning speed and path profiles during curve approach and curve negotiation, and (2) nonlinear versus linear aspects of control.

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.

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.

Computational Techniques Used in the Driver Performance Model of the Interactive Highway Safety Design Model

2001 ◽  
Vol 1779 (1) ◽  
pp. 17-25 ◽  
Author(s):  
William H. Levison ◽  
Ozgur Simsek ◽  
Alvah C. Bittner ◽  
Steven J. Hunn
Keyword(s):  
Computer Aided Design ◽  
Driving Simulator ◽  
Research Area ◽  
Highway Safety ◽  
Performance Model ◽  
Design Model ◽  
Computational Techniques ◽  
Design Environment ◽  
Driver Performance ◽  
Safety Design

The Interactive Highway Safety Design Model (IHSDM) is a high-priority research area for FHWA. IHSDM is a software system for evaluating the safety of alternative highway designs in a computer-aided design environment. The initial phase of this research program is to develop IHSDM for use in the design of two-lane rural highways. IHSDM includes a driver-vehicle module that simulates the moment-to-moment actions of a single driver-vehicle unit. Reviewed are the computational approaches that have guided the implementation of the driver performance model (DPM) that along with a vehicle model and other components constitute the driver-vehicle module. Five major computational functions of DPM are reviewed: perception, speed decision, path decision, speed control, and path control. Comparison of model results with data from a driving simulator demonstrates the ability of DPM to account for the horizontal curve deflection angle on the speed profile.

Empirical Investigation of Interactive Highway Safety Design Model Accident Prediction Algorithm: Rural Intersections

2003 ◽  
Vol 1840 (1) ◽  
pp. 78-86 ◽  
Author(s):  
Craig Lyon ◽  
Jutaek Oh ◽  
Bhagwant Persaud ◽  
Simon Washington ◽  
Joe Bared
Keyword(s):  
Research Effort ◽  
Methodological Approach ◽  
The United States ◽  
Highway Safety ◽  
Design Model ◽  
Prediction Algorithm ◽  
Parameter Estimates ◽  
Wide Range ◽  
Safety Design ◽  
The Impact

One major gap in transportation system safety management is the ability to assess the safety ramifications of design changes for both new road projects and modifications to existing roads. To fulfill this need, FHWA and its many partners are developing a safety forecasting tool, the Interactive Highway Safety Design Model (IHSDM). The tool will be used by roadway design engineers, safety analysts, and planners throughout the United States. As such, the statistical models embedded in IHSDM will need to be able to forecast safety impacts under a wide range of roadway configurations and environmental conditions for a wide range of driver populations and will need to be able to capture elements of driving risk across states. One of the IHSDM algorithms developed by FHWA and its contractors is for forecasting accidents on rural road segments and rural intersections. The methodological approach is to use predictive models for specific base conditions, with traffic volume information as the sole explanatory variable for crashes, and then to apply regional or state calibration factors and accident modification factors (AMFs) to estimate the impact on accidents of geometric characteristics that differ from the base model conditions. In the majority of past approaches, AMFs are derived from parameter estimates associated with the explanatory variables. A recent study for FHWA used a multistate database to examine in detail the use of the algorithm with the base model-AMF approach and explored alternative base model forms as well as the use of full models that included nontraffic-related variables and other approaches to estimate AMFs. That research effort is reported. The results support the IHSDM methodology.

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