Roadside Hardware Replacement Analysis: User Guide (2021) / Chapter Skim
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3 network safety. Appreciating the underlying risk reductions and costs of upgrading are fundamental to developing effective upgrading policies.
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4 Table 1. Roadside Hardware Replacement Analysis Steps.
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5 Table 1. Roadside Hardware Replacement Analysis Steps.
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6 Figure 1. Roadside Hardware Replacement Analysis Workbook.
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7 3.2 RISK ASSESSMENTS FOR EXISTING HARDWARE Knowing how well the existing hardware is performing is a necessary first step in the assessment of the roadside hardware replacement analysis process. Performance of roadside hardware in this analysis procedure is defined as the risk of observing a fatal or serious injury policereported crash involving the subject roadside hardware given a crash occurs.
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8 3.2.3 Step 3: Number of Fatal and Serious Injury Crashes with Existing Hardware The number of fatal and serious injury crashes for each type of existing roadside hardware to be considered is a subset of the data collected in the Step 2. Fatal and serious injuries are assessed using the injury scale used on most police reports.
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9 3.2.5 Step 5: Mean Risk and Confidence Interval The risk of a fatal or serious injury crash involving the subject existing hardware (REHj) is determined by dividing the number of fatal and serious injury crashes found in Step 3 by the total number of crashes found in Step 2 as follows: REH = NFSCNC → Step5 = Step3Step2 REHj is a direct measure of the performance of the existing hardware since it describes the risk of a fatal or serious injury based on the observed police-reported crash data obtained earlier in Step 1.
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10 device. On the other hand, if the 85th CI was ±0.0020 for guardrail B, the difference is likely a real difference in performance.
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11 then be extrapolated based on the total miles of roadway in the area. For guardrails, median barriers, and bridge railings the quantity is entered in ft whereas for terminals, transitions, and other discreet objects they entered in units of "each." Enter the quantity of existing hardware in the same area used to collect police-reported crash data (QEHj)
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12 The police-reported crash rate (CREHj) is automatically calculated and entered into the box for Step 8.
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13 do not depend on how the AADT is estimated, only the value in the design year is required. One common method for projecting future traffic volume is simple geometric growth as follows: AADT = AADT ∙ (1 + G)
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14 3.5 ECONOMIC ANALYSIS The last portion of the analysis is an economic analysis where the expected annual number of the fatal and serious crashes avoided on the project are transformed into a dollar value and compared to the total cost of replacing the existing hardware with new upgraded hardware. 3.5.1 Step 17: Annual Number of Fatal and Serious Injury Crashes Avoided The reduction of risk resulting from installing the new replacement hardware is expected to result in fewer fatal and serious injury crashes.
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From page 21... ...
15 2016 the recommend value was $9.6 million (17)
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