Questions? Call 800-624-6242 About | Ordering | New Menu | Items in cart [0] SEARCH

Rights & Permissions Free PDF Access Sign in to download PDF book and chapters Free Resources Display this book on your site! Related Titles NCHRP Report 613: Guidelines for Selection of Speed Reduction Treatments at High-Speed Intersections NCHRP Report 518: Safety Evaluation of Permanent Raised Pavement Markers Other Related Titles NCHRP Report 641: Guidance for the Design and Application of Shoulder and Centerline Rumble Strips (2009) National Cooperative Highway Research Program (NCHRP) Citation Manager Export the bibliographic data for this book in your chosen format Web Search Builder Use this book's key terms to search within this book, across our collection, or across the Web. Skim This Chapter Skim this chapter and use this chapter's key terms to search within this book. Reference Finder Paste in your own text to find books that relate to your topic. Citation Manager Donnell, Eric T, Garvey, Philip M, Bauer, Karin M, Harwood, Douglas W, Gilmore, David K, Dunn, Joanna M, Lyon, Craig, Persaud, Bhagwant, Bokenkroger, Courtney D, Torbic, Darren John, Hutton, Jessica M, Ronchetto, J J, Sommer, H J, Transportation Research Board. "Appendix E - SPF Results for TOT, FI, SVROR, and SVROR FI Crashes on Selected Roadways Without Shoulder Rumble Strips." NCHRP Report 641: Guidance for the Design and Application of Shoulder and Centerline Rumble Strips. Washington, DC: The National Academies Press, 2009. Please select a format: Page 19   E-mail Share on facebook Facebook Share on delicious Delicious Share on stumbleupon Stumble Share on twitter Twitter More Sharing ServicesMore Page 19 Front Matter (R1-R251) Appendix D - Roadside Hazard Rating Category Descriptions (14-18) Appendix E - SPF Results for TOT, FI, SVROR, and SVROR FI Crashes on Selected Roadways Without Shoulder Rumble Strips (19-21) Appendix F - GLM Analysis Results for Safety Effectiveness of Shoulder Rumble Strips (22-26) Appendix G - GLM Analysis Results for Effect of Shoulder Rumble Strip Offset and Recovery Area on Safety (27-30) Appendix H - SPF Results for TOT, FI, and SSOD Crashes on Selected Roadways Without Centerline Rumble Strips (31-32) Abbreviations used without definitions in TRB publications (33-33)

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 19
158 APPENDIX E SPF Results for TOT, FI, SVROR, and SVROR FI Crashes on Selected Roadways Without Shoulder Rumble Strips This appendix presents the SPF results developed based on It should be noted that the analyses for SVROR crashes all nontreatment sites (i.e., sites without shoulder rumble strips: includes SVROR crashes to the right and to the left. No effort BA-No RS and CS-No RS) in the four roadway categories for is made to distinguish crashes by side of the road; however, the four crash types of interest (Tables E-1 to E-4). These SPFs by including RHR for both the outside and inside shoulders/ were developed using negative binomial regression analysis. roadsides of divided highways, the analyses account for the Each line in each table provides the regression coefficients and differences between ROR crashes to the right and left. Also, their precision estimates for a given SPF. For example, using for states that treat both sides of a divided highway as sepa- Table E-1 for urban freeways in Pennsylvania: rate sites (i.e., Missouri and Pennsylvania), the RHR variables in the models represent the values for a single side of the divided Expected total crashes mi yr highway. When both sides of a divided highway are treated as = exp ( -8.17 + 0.83 ln ADT + 0.10 RHR Out + 0.19 RHR IN ) a single site (i.e., Minnesota sites), the RHR variables in the model represent average values for both directions of travel. = e -8.17 × ADT 0.83 × e0.10 RHR_Out × e0.10 RHR_In Similarly, the RHR variable in the model for rural two-lane An empty cell in a table indicates the corresponding regres- roads represents the average RHR for both sides of the roadway. sion coefficient was not statistically significant at the 0.15 level Thus, the analysis accounts for SVROR right and SVROR left or the coefficient's sign was not of the expected direction. Note crashes, without necessarily distinguishing between the two that inside RHR does not apply to rural two-lane roads. crash types.

OCR for page 20
Table E-1. SPF results for TOT crashes based on all nontreatment sites. Number Intercept lnADT Outside RHR Inside RHR Overdispersion of 2 Roadway type State sites a b R LR Estimate SE Estimate SE p­value Estimate SE p­value Estimate SE p­value Estimate SE Urban freeways PA 90 ­8.17 1.07 0.83 0.11 <.0001 0.10 0.05 0.051 0.19 0.05 0.0001 0.10 0.03 0.70 MO 35 ­11.69 2.79 1.31 0.28 <.0001 0.16 0.05 0.37 Rural freeways c PA 34 ­0.15 2.59 0.08 0.27 0.782 0.10 0.06 0.002 MN 33 ­8.10 1.36 0.87 0.15 <.0001 0.23 0.08 0.005 0.11 0.04 0.62 Rural multilane divided highways (nonfreeways) MO 26 ­12.84 4.42 1.50 0.47 0.002 0.64 0.19 0.25 PA 13 ­13.01 6.58 1.48 0.69 0.033 0.28 0.15 0.26 MN 56 ­4.75 0.58 0.44 0.08 <.0001 0.33 0.07 <.0001 0.21 0.06 0.60 Rural two­lane roads MO 37 ­5.95 2.68 0.51 0.25 0.039 0.61 0.34 0.075 1.49 0.39 0.15 PA 110 ­4.99 0.91 0.62 0.11 <.0001 0.31 0.06 0.23 a SE: standard error of estimate. b p-value: significance level. c ADT not significant at 0.15 significance level. Table E-2. SPF results for FI crashes based on all nontreatment sites. Number Intercept lnADT Outside RHR Inside RHR Overdispersion of 2 Roadway type State sites Estimate SEa Estimate SE p­valueb Estimate SE p­value Estimate SE p­value Estimate SE R LR Urban freeways PA 90 ­8.42 1.32 0.77 0.13 <.0001 0.11 0.06 0.079 0.22 0.06 0.0001 0.12 0.04 0.61 MO 35 ­13.37 3.20 1.36 0.32 <.0001 0.12 0.05 0.36 Rural freeways c PA 34 ­4.54 3.38 0.45 0.35 0.199 0.10 0.09 0.05 Rural multilane divided MN 33 ­8.00 1.74 0.75 0.19 <.0001 0.20 0.11 0.064 0.15 0.06 0.44 highways MO 26 ­18.77 4.73 2.01 0.51 <.0001 0.46 0.20 0.35 (nonfreeways) PA 13 ­13.12 7.75 1.42 0.82 0.082 0.33 0.20 0.19 MN 56 ­5.71 0.65 0.43 0.09 <.0001 0.33 0.07 <.0001 0.08 0.05 0.59 Rural two­lane roads MO 37 ­7.03 2.65 0.44 0.25 0.078 0.77 0.32 0.018 1.24 0.36 0.18 PA 110 ­6.05 1.08 0.68 0.13 <.0001 0.38 0.09 0.20 a SE: standard error of estimate. b p­value: significance level. c ADT not significant at 0.15 significance level.

OCR for page 21
Table E-3. SPF results for SVROR crashes based on all nontreatment sites. Number Intercept lnADT Outside RHR Inside RHR Overdispersion of p­ a b 2 Roadway type State sites Estimate SE Estimate SE p­value Estimate SE p­value Estimate SE value Estimate SE R LR Urban freeways PA 90 ­6.22 1.23 0.60 0.12 <.0001 0.11 0.06 0.083 0.12 0.06 0.030 0.10 0.03 0.46 MO 35 ­10.23 3.71 1.09 0.37 0.003 0.26 0.08 0.19 Rural freeways c PA 34 0.22 0.10 0.16 0.09 nc Rural multilane MN 33 ­9.81 1.82 0.99 0.19 <.0001 0.17 0.07 0.44 divided highways MO 26 ­16.28 4.81 1.76 0.52 0.001 0.53 0.19 0.29 (nonfreeways) PA 13 ­20.34 7.42 2.21 0.78 0.005 0.19 0.14 0.37 d MN 56 ­3.62 0.74 0.07 0.10 0.475 0.49 0.09 <.0001 0.21 0.10 0.40 d Rural two­lane roads MO 37 ­5.68 2.77 0.25 0.26 0.331 0.82 0.35 0.019 1.40 0.39 0.16 PA 110 ­3.05 1.11 0.34 0.13 0.012 0.48 0.10 0.05 a SE: standard error of estimate. b p-value: significance level. c 2 Means model; R LR not calculated. d ADT not significant at 0.15 significance level. Table E-4. SPF results for SVROR FI crashes based on all nontreatment sites. Number Intercept lnADT Outside RHR Inside RHR Overdispersion of 2 Roadway type State sites Estimate SEa Estimate SE p­valueb Estimate SE p­value Estimate SE p­value Estimate SE R LR Urban freeways PA 90 ­6.88 1.36 0.62 0.13 <.0001 0.11 0.08 0.130 0.12 0.05 0.25 MO 35 ­10.33 4.04 1.01 0.40 0.012 0.21 0.09 0.15 Rural freeways c PA 34 ­0.52 0.11 0.14 0.12 nc MN 33 ­8.61 2.26 0.79 0.24 0.001 0.23 0.10 0.25 Rural multilane divided highways (nonfreeways) MO 26 ­17.50 5.08 1.82 0.54 0.001 0.44 0.20 0.28 PA 13 ­20.03 9.38 2.11 0.99 0.032 0.33 0.22 0.26 d MN 56 ­3.73 1.06 0.15 0.14 0.258 0.58 0.24 0.02 d Rural two­lane roads MO 37 ­6.00 2.61 0.13 0.26 0.611 0.93 0.31 0.003 1.10 0.39 0.21 PA 110 ­3.58 1.25 0.32 0.15 0.034 0.49 0.13 0.04 a SE: standard error of estimate. b p-value: significance level. c 2 Means model; R LR not calculated. d ADT not significant at 0.15 significance level.