Multi-State In-Service Performance Evaluations of Roadside Safety Hardware (2022) / Chapter Skim
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13 APPENDIX: UTAH DEPARTMENT OF TRANSPORTATION ISPE EVALUATION OF LONGITUDINAL BARRIER TABLE OF CONTENTS List of Figures ............................................................................................................................... 13 List of Tables ................................................................................................................................
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14 Figure 7: Initial contact points, expected indicated by green, unexpected indicated by red. .........33 Figure 8.
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15 CHAPTER 1: INTRODUCTION A routine In-Service Performance Evaluation (ISPE) was undertaken using the uniform criteria presented in the ISPE Guidelines Document [NCHRP Research Report 1010: In-Service Performance Evaluation: Guidelines for the Assembly and Analysis of Data (Carrigan and Ray 2022)
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16 Table 1. Longitudinal Barrier Types used in Utah.
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17 W-Beam with steel blocks (NCHRP 230 W-Beam) W-beam barrier with steel blocks.
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18 CHAPTER 3: STUDY PERIOD AND REGION This study was a routine ISPE of longitudinal barrier. Crash data collected for this ISPE included all reported crashes occurring on the roughly 6,000 centerline miles of state-maintained roads within the State of Utah.
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19 CHAPTER 4: AVAILABLE DATA The UTAPS-CDI crash database for 2016 through 2020 was used in conjunction with the 2019 statewide roadside safety hardware asset inventory. This ISPE analysis was performed by staff from the UDOT Traffic & Safety Division, and the original data used in the analysis is available upon request.
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20 may have been associated with two different runs of barrier, but they are the same type)
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21 Table 2. Compiled ISPE Dataset and Source Material.
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22 Table 3. ISPE Dataset MAX_SEV Equivalence Table.
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23 Table 4. Equivalency of the State Motor Vehicle Body Type to Dataset Variables.
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24 Table 5. ISPE Dataset PostHE Equivalence Table.
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25 Table 6. NAME Equivalence Table to Particular Hardware NAME Jurisdiction's Description Test Level a Box Beam NCHRP-350 TL 3 b Brifen 4 Rope O-Post Cable MASH 4 c Cable Brifen NCHRP-350 TL 3 d Cable Trinity NCHRP-350 TL 3 e Constant Slope Concrete Barrier MASH TL 3 f Crescent Rail Pre-requirements g Double Sided NCHRP-350 TL 3 h Jersey Barrier 12.5 / 230 / Precast Jersey 230 NCHRP-230 TL 3 i Jersey Barrier 20 / 350 / Precast Jersey 350 NCHRP-350 TL 3 j MGS W-Beam MASH TL 3 k Other - l Jersey Parapet NCHRP-350 TL 3 m Point Hazard - n W-Beam NCHRP-350 TL 3 p W-Beam w/ Motorcycle Barrier NCHRP-350 TL 3 q CIP Jersey NCHRP-350 TL 3 r Parapet NCHRP-350 TL 3 s Precast Half Barrier NCHRP-350 TL 3 t Not used - u 42" Single Slope Parapet MASH TL 4 v CIP Constant Slope MASH TL 3 w Not used - x Precast 42" Constant Slope NCHRP-350 TL 3 y Not used - z Not used - 99 Unknown -
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26 CHAPTER 5: PERFORMANCE OUTCOMES, EVALUATION MEASURES, AND CONDITIONS 5.1 FULL DATASET An ISPE first considers the availably of known data through Condition 1. Condition 1 is met when the sampled data are not biased and the statistical power of the study is maximized.
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27 Table 7. Evaluation of Conditions 1, 2, and 3 for each Evaluation Measure.
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28 consideration of the 85th percentile confidence interval as suggested by the NCHRP Project 2233 ISPE Guidelines Document. PAL1 evaluates the performance of the longitudinal barriers across the full dataset.
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29 Table 8. Performance Assessment by Level.
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30 5.2 DATASET STRATIFIED BY VALUES OF NAME The hardware involved in each reported crash was identified as discussed in Chapter 4. There are 21 possible values of NAME based on the hardware inventory.
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31 CHAPTER 6: SUMMARY AND CONCLUSIONS This chapter includes interpretation of results, conclusions, and recommendations for future ISPEs in Utah. 6.1 INTERPRETING RESULTS OF FULL DATASET Comparison of post impact harmful events for the full dataset (i.e., PAL1)
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32 secondary collisions on the roadside (Evaluations J) , therefore, the confidence intervals are wide and these values lack precision.
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33 0.000 Eval H Eval H Eval H Eval H Any Harmful Event First Harmful Event Most Harmful Event First & Only Harmful Event Figure 6. Proportion of KA crashes for Evaluation Measure H (vehicle mix)
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34 1.00 1.00 0.30 0.30 0.20 0.20 0.100.10 0.000.00 Evaluation M R2 Evaluation M ES Figure 8. Proportion of longitudinal barrier crashes with an unexpected impact orientation (left)
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37 Brifen Trinity Slope Sided Barrier 230Barrier 350 [923]
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38 0.2000 0.1800 0.1600 0.1400 0.1200 0.1000 0.0800 0.0600 0.0400 0.0200 0.0000 Concrete [397]
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39 0.2000 0.1800 0.1600 0.1400 0.1200 0.1000 0.0800 0.0600 0.0400 0.0200 0.0000 Barrier [268]
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41 based on both the geometric considerations as well as driver behaviors. Second, cable barrier is a much less abrupt impact and as such vehicles may not "bounce" as much when they are hit, and the crashed vehicle is not redirected back into the roadway as often.
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42 study of longitudinal barriers found lower risks of fatal and serious injuries with longitudinal barriers in Utah. These results provide added benefit during the updating of current UDOT roadside design and hardware placement/selection procedures.
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43 REFERENCES Carrigan, C
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44 ISPE SUMMARY OF DATA AND RESULTS SHEETS Evaluation F (Rollover) ISPE Project ID: BARRIER20210826 Test Level: TL3 CI z Value: 1.44 Performance Assessment Level 1 (PAL1)
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45 Rollover - Other 3 11 27 27 30 0 98 5% R2 0.0518 0.0449 0.0596 None 2 20 116 236 1420 1 1795 95% PAL 4 Distribution and Results of PostHE for TOTAL limited by VEH_TYPE & SPEED_LIMIT K A B C O U Totals Dist C.I.
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46 K PAL2 Distribution and Result limited by VEH_TYPE for AHE A B C O U Totals Dist C.I.
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47 First Harmful Event 18 120 683 1277 6914 2 9014 R2_FHE 0.0153 0.0136 0.0173 Most Harmful Event 9 101 641 1242 7051 2 9046 R2_MHE 0.0122 0.0106 0.0139 First and Only Harmful Event 5 57 419 882 5324 2 6689 R2_FOHE 0.0093 0.0077 0.0111 K A PAL2 Distributi B C on Limited O by VE U H_TYPE Totals C.I.
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48 Performance Assessment Level 1 (PAL1) Distribution and Results of PostHE not limited K A B C O U Totals Dist C.I.
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49 ISPE Project ID: BARRIER20210826 Test Level: TL3 CI z Value: 1.44 Performance Assessment Level 1 (PAL1) Distribution and Results of PostHE not limited K A B C O U Totals Dist C.I.
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50 PAL 4 Distribution and Results of PostHE for TOTAL limited by VEH_TYPE & SPEED_LIMIT K A B C O U Totals Dist C.I.
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NAME 51 Evaluation F (Rollover) for Each Level of NAME BARRIER20210 ISPE Project ID: 826 Test Level: CI z Value: NAME PAL1F, R2 PAL2F, R2 PAL3F, R2 PAL4F, R2 a b 0.0400 (0.0106,0.1399)
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NAME 52 Evaluation H (Vehicle Mix) for AHE and Each Level of NAME BARRIER20210 ISPE Project ID: 826 Test Level: CI z Value: PAL1H, R2_AHE PAL2H, R2_AHE PAL3H, R2_AHE PAL4H, R2_AHE a b 0.0000 (0.0000,0.0545)
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NAME 53 Evaluation H (Vehicle Mix) for FHE and Each Level of NAME BARRIER20210 ISPE Project ID: 826 Test Level: CI z Value: PAL1H, R2_FHE PAL2H, R2_FHE PAL3H, R2_FHE PAL4H, R2_FHE a b 0.0000 (0.0000,0.0609)
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NAME 54 Evaluation H (Vehicle Mix) for MHE and Each Level of NAME BARRIER20210 ISPE Project ID: 826 Test Level: CI z Value: PAL1H, R2_MHE PAL2H, R2_MHE PAL3H, R2_MHE PAL4H, R2_MHE a b 0.0000 (0.0000,0.0575)
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55 Evaluation H (Vehicle Mix) for FOHE and Each Level of NAME BARRIER20210 ISPE Project ID: 826 Test Level: CI z Value: PAL1H, R2_FOHE PAL2H, R2_FOHE PAL3H, R2_FOHE PAL4H, R2_FOHE a b 0.0000 (0.0000,0.0899)
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56 Evaluation J (Secondary Impact on Roadside) for Each Level of NAME BARRIER20210 ISPE Project ID: 826 Test Level: CI z Value: NAME PAL1J, R2 PAL2J, R2 PAL3J, R2 PAL4J, R2 a b 0.0000 (0.0000,0.0795)
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57 Evaluation K (Secondary Impact on Road) for Each Level of NAME BARRIER20210 ISPE Project ID: 826 Test Level: CI z Value: NAME PAL1K, R2 PAL2K, R2 PAL3K, R2 PAL4K, R2 a b 0.1333 (0.0674,0.2467)
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58 Evaluation K (Secondary Impact on Road) for Each Level of NAME BARRIER20210 ISPE Project ID: 826 Test Level: CI z Value: NAME PAL1K, R2 PAL2K, R2 PAL3K, R2 PAL4K, R2 a b 0.1333 (0.0674,0.2467)
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