Guidelines for Shielding Bridge Piers (2018) / Chapter Skim
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From page 54... ...
54 Discussion of Proposed RDG Occupant Protection Guidelines Appendix B: Proposed RDG Occupant Protection Guidelines provides a proposal regarding occupant protection for inclusion in a future edition of the RDG. Unlike the AASHTO LRFD Bridge Design Specifications, the RDG does not contain a single section that is applicable only to impacts with bridge piers.
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55 1. The annual frequency of passenger vehicle encroachments in each direction (PVEi)
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56 Two-Way AADT Undivided Highways PT veh/day 5 10 15 20 25 30 35 40 1,000 0.0165 0.0157 0.0148 0.0139 0.0130 0.0122 0.0113 0.0104 2,000 0.0268 0.0254 0.0240 0.0226 0.0212 0.0198 0.0183 0.0169 3,000 0.0326 0.0309 0.0292 0.0275 0.0258 0.0240 0.0223 0.0206 4,000 0.0353 0.0334 0.0316 0.0297 0.0279 0.0260 0.0241 0.0223 5,000–41,000 0.0358 0.0339 0.0320 0.0301 0.0282 0.0264 0.0245 0.0226 42,000 0.0371 0.0351 0.0332 0.0312 0.0293 0.0273 0.0254 0.0234 43,000 0.0380 0.0360 0.0340 0.0320 0.0300 0.0280 0.0260 0.0240 44,000 0.0389 0.0368 0.0348 0.0327 0.0307 0.0286 0.0266 0.0245 45,000 0.0397 0.0377 0.0356 0.0335 0.0314 0.0293 0.0272 0.0251 ≥46,000 0.0406 0.0385 0.0364 0.0342 0.0321 0.0299 0.0278 0.0257 Two-Way AADT Divided Highways PT veh/day 5 10 15 20 25 30 35 40 1,000 0.0114 0.0108 0.0102 0.0096 0.0090 0.0084 0.0078 0.0072 5,000 0.0485 0.0459 0.0434 0.0408 0.0383 0.0357 0.0332 0.0306 10,000 0.0789 0.0747 0.0706 0.0664 0.0623 0.0581 0.0540 0.0498 15,000 0.0962 0.0912 0.0861 0.0810 0.0760 0.0709 0.0658 0.0608 20,000 0.1044 0.0989 0.0934 0.0879 0.0824 0.0769 0.0714 0.0659 24,000–47,000 0.1062 0.1006 0.0950 0.0894 0.0838 0.0782 0.0727 0.0671 50,000 0.1143 0.1082 0.1022 0.0962 0.0902 0.0842 0.0782 0.0722 55,000 0.1257 0.1191 0.1125 0.1058 0.0992 0.0926 0.0860 0.0794 60,000 0.1371 0.1299 0.1227 0.1155 0.1082 0.1010 0.0938 0.0866 65,000 0.1485 0.1407 0.1329 0.1251 0.1173 0.1094 0.1016 0.0938 70,000 0.1600 0.1515 0.1431 0.1347 0.1263 0.1179 0.1094 0.1010 75,000 0.1714 0.1624 0.1533 0.1443 0.1353 0.1263 0.1173 0.1082 80,000 0.1828 0.1732 0.1636 0.1540 0.1443 0.1347 0.1251 0.1155 85,000 0.1942 0.1840 0.1738 0.1636 0.1533 0.1431 0.1329 0.1227 ≥ 90,000 0.2057 0.1948 0.1840 0.1732 0.1624 0.1515 0.1407 0.1299 †Encroachment data are not available for one-way roadways.Traditionally, one-way roadways have been evaluated using the encroachment model for divided highways.The one-way AADT value should be multiplied by 2 and used to determine PV ENCRDIV BASE for use in the remaining calculations. Table 24.
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From page 57... ...
57 smoothed Cooper data used in the heavy-vehicle portion of the guidelines is also used here for the same reasons. Heavyvehicle encroachments were already considered in the LRFD portion of the guidelines; therefore, only passenger vehicles are considered in this step.
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58 column with a variable diameter. The pier component was studied at a variety of offsets measured from the edge of the travel lane to the pier face.
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59 The probability of a crash for each level of offset and diameter was determined as shown in Figure 32. The dependent variable [P(C|PVEi)
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60 4.2.4 Probability of a Severe or Fatal Crash Given a Collision with an Unshielded Pier Component: P(KACUSP|C) Next a model for the conditional probability of a severe or fatal (KA)
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61 "8 – Ran off road right," "9 – Ran off road left," "10 – Cross median/centerline," or "11 – Downhill runaway" in Event 1 followed by "27" in Event 2 and a blank in Event 3 were considered clean bridge-pier crashes. Washington.
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63 State/Years Number Reported Cases Number Estimated Unreported EFCCR65 Bridge Pier First and Only Object Struck NJ 2001–2013 25 72 0.0075 NC 2003–2012 52 72 0.0889 OH 2000–2012 86 203 0.0623 WA 1993–1996 and 1999–2011 46 60 0.3303 WY 2008–2013 30 113 0.0473 Combined 239 520 0.0784 Table 31. Summary of bridge pier EFCCRs.
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64 4.2.4.4 Step 3: Estimate Unreported Crashes Step 3 of the EFCCR procedure includes the determination or estimation of the percentage of unreported crashes. These values are added to the field-observed crashes to obtain the full distribution of both reported and unreported crashes.
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65 Table 38. Counts are not estimated when there are no data at a PSL level; therefore, some cells in Table 38 contain no values.
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66 The resulting value can be used in the guidelines and adjusted using the site-specific PSL, as follows: KA KA 65 PSLPSL CUSP 65 3 3P C P C ii ( )
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From page 67... ...
67 crashes/edge-mile/year. AASHTO SCOBS T7 and the AASHTO Technical Committee on Roadside Safety (TCRS)
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