SWUTC Research Project Description
Calibration of the Louisiana Highway Safety Manual
University: Louisiana State University
Principal Investigator:
Brian Wolshon
Gulf Coast Research Center for Evacuation and Transportation Resiliency
(225) 578-5247
Project Monitor:
Dan Magri
Louisiana Department of Transportation and Development
Baton Rouge, LA
Funding Source: USDOT
Total Project Cost: $75,000
Project Number: 600451-00102
Date Started: 11/1/12
Estimated Completion Date: 10/31/13
Project Summary
Project Abstract:
The State of Louisiana consistently ranks near the bottom in national statistics regarding highway safety, particularly traffic crash related fatalities. To counter these conditions, the Louisiana Department of Transportation and Development (DOTD) has initiated several programs over the recent decade. The past several decades have also seen many new highway safety related innovations on a national‐level. One of the most promising recent developments has been the recent publication of the Highway Safety Manual (HSM) by the American Association of State Highway and Transportation Officials (AASHTO). The HSM includes analytical tools and techniques for quantifying the safety effects of planning and design alternatives and configurations and operations and maintenance decisions. However, since the HSM has been developed based on national trends and statistics, it must be “adjusted” for local use. These adjustments allow it to better fit local conditions. The objective of this project is to calibrate the Part C predictive model as outlined in Appendix A of the Highway Safety Manual for roadway segments in Louisiana, specifically, Rural Two‐Lane‐Two‐Way Roads; Rural Multilane Highways; and Urban and Suburban Arterials. A single calibration for each of the aforementioned roadway segments will be conducted and applicable to the entire state of Louisiana. In addition, a comparative analysis will be conducted to compare the SPFs developed specifically for Louisiana to the SPFs determined as a result of calibrating the current HSM models to Louisiana conditions. Among the outcomes of this research will be to recommend whether the Louisiana DOTD should use the state specific SPFs or the calibrated SPFs for future projects.
Project Objectives:
The objective of this project is to calibrate the Part C predictive model as outlined in Appendix A of the Highway Safety Manual for roadway segments in Louisiana, specifically, Rural Two-Lane-Two-Way Roads; Rural Multilane Highways; and Urban and Suburban Arterials. A single calibration for each of the aforementioned roadway segments will be conducted and applicable to the entire state of Louisiana. In addition, a comparative analysis will be conducted to compare the SPFs developed specifically for Louisiana to the SPFs determined as a result of calibrating the current HSM models to Louisiana conditions. The development of the Louisiana specific SPFs will be performed by others and is not part of this scope of work. Among the outcomes of this research will be to recommend whether the Louisiana DOTD should use the state specific SPFs or the calibrated SPFs for future projects.
Task Descriptions:
Task 1: Literature and State-of-the-Practice Review
Task 2: Data Collection and Analysis
Task 3: Prepare and present the project review committee with an interim report
Task 4: HSM Calibration
Task 5: Comparative Analysis
Task 6: Final Report
Implementation of Research Outcomes:
In this research, Highway Safety Manual (HSM) predictive model calibration factors were calculated using a series of iterations in which the amount of data and assumed crash conditions were varied from one iteration to the next. The overall results of this work demonstrate the extent of the variability and sensitivity of HSM calibration factors to the inclusion of data that may or may not be included in roadway databases and how crashes that occur within various distances away from intersections are included or excluded.
Among the general findings was that the more data that was included in the computational process, the more reliable the calibration factor became. A somewhat unexpected finding, however, was that reasonably accurate calibration factors may be attainable without enormous time expenditures.
The results of this research were transferred to the Louisiana Transportation Research Center and the Louisiana Department of Transportation and Development for application in their roadway crash prediction models. It is anticipated that the factors developed from this research will serve these two entities for the next several years, before ultimately being updated and replaced.
Products developed by this research:
Presentation: Calibration of the Highway Safety Manual for Louisiana, Brian Wolshon, presented to the 2014 Louisiana Transportation Safety Summit, Baton Rouge, LA, March 2014
Presentation: Development of Louisiana-Specific Highway Safety Crash Calibration Factors, Brian Wolshon, presented to the Deep South Section Meeting of the Institute of Transportation Engineers, Baton Rouge, LA, February 2014.
Journal Article Submitted for Review: Influences of Data Inclusion on HSM Calibration and Crash Prediction, Bridget Robicheaux and Brian Wolshon, under review by the Journal of Transportation Safety and Security.
Impacts/Benefits of Implementation:
The past decade has seen many new highway safety related advancements on a national level. Among the most significant of these was the 2010 publication of the Highway Safety Manual (HSM) by the American Association of State Highway and Transportation Officials (AASHTO). The HSM includes analytical tools and techniques for quantifying the safety effects of planning options; evaluating safer design alternatives; and supporting operational and maintenance decisions.
This research effort informs and supports future users of the HSM by examining how data inclusion affects the HSM calibration factor development process. This is important because, given the limitations of data availability and collection/coding methods, the research focus turned to testing methods that might be used to address these issues and better understand their quantitative effects on the resulting factors. Ultimately, this research could have a long-term impact on the use of the HSM by State DOT’s in accurately evaluating safety. Better understanding of safety and the impact of roadway factors can lead less hazardous roadways and fewer motor vehicle related fatalities nationwide.
Web Links:
Final Technical Report