Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers (2022) / Chapter Skim
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From page 153... ...
E-1 A P P E N D I X E Probability of Passing Across the Opposing Lanes (THREOL) CONTENTS Chapter 1 Introduction Chapter 2 Model Considerations Avoiding Measuring the Same Variable Twice Method Chapter 3 Data Used for Modeling Chapter 4 Model Development Chapter 5 Application of Modeling Results References
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E-2 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers Traffic volume in the opposing direction is thought to affect the probability of a crossmedian crash, P(CMC)
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Probability of Passing Across the Opposing Lanes (THREOL) E-3 The conditional probability of a cross-median crash (CMC)
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E-4 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers In other words, the probability of both a crossover crash (CO) and MRE compared with the P(MRE)
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Probability of Passing Across the Opposing Lanes (THREOL) E-5 explanatory variables to the response variable using the method of maximum likelihood to quantify the magnitude of each predictor relationships.
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E-6 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers using the recorded route and milepost of each crash. The resulting data set included a list of segments.
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Probability of Passing Across the Opposing Lanes (THREOL) E-7 Table E-1 Descriptive Statistics for P(CMC)
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E-8 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers Recall the number of crashes per year was tabulated in the data set. A negative binomial model was fit to the dataset of head-on crashes and the log of the segment length in miles was included as an offset to allow for the frequency of head-on crashes to be evaluated per year per mile.
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Probability of Passing Across the Opposing Lanes (THREOL) E-9 Table E-2 Negative Binomial Model for Cross-Over Crashes Coefficients: Parameter Estimate Standard Error P-Value 95% Confidence Interval (Intercept)
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E-10 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers • Consider only segments where the DOC = 0 (21,918)
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Probability of Passing Across the Opposing Lanes (THREOL) E-11 Table E-4 Negative Binomial Model for Cross-Over Crashes Coefficients: Parameter Estimate Standard Error P-value 95% Confidence Interval (Intercept)
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E-12 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers Further, this model must be offset by MVMT for use with the Cooper data model. The simpler model where the confounders are explicitly controlled through limiting segments considered, as documented in Table E-4, is preferred because (1)
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Probability of Passing Across the Opposing Lanes (THREOL) E-13 Table E-6 Primary Right Base Encroachments per MVMT for Four-Lane Divided Highways (Ray 2012)
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E-14 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers used. The result for an estimate of the encroachment rate from one left-side encroachment on a four-lane divided highway is, therefore, as follows: Finally, half the frequency of CO/MVMT is then divided by the left-encroachment frequency to determine the probability of a CMC given a CME has occurred P(CMC|CME)
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Probability of Passing Across the Opposing Lanes (THREOL) E-15 assumed to be one.
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E-16 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers If a vehicle enters opposing lanes but does not have a crash with opposing traffic, the vehicle occupants will not experience any harm associated with entering opposing lanes. The proportion of the vehicles passing through, rather than having a crash must therefore be tabulated (i.e., THREOL)
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Probability of Passing Across the Opposing Lanes (THREOL) E-17 REFERENCES Carrigan, Christine E
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Abbreviations and acronyms used without denitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FAST Fixing America's Surface Transportation Act (2015) FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration GHSA Governors Highway Safety Association HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012)
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