Skip to main content

Currently Skimming:


Pages 35-106

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 35...
... 35   9.1 Study 1 and Study 2: Using Deterministic and Probabilistic Tools to Forecast Key Asset Management Variables at a DOT State transportation agencies are required to prepare financial plans for their 10-year TAMPs. These plans need to include forecasts of investments needed, the corresponding bridge and pavement conditions, and the revenues the agency expects to receive during the forecast period.
From page 36...
... 36 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research 9.1.1 Pilot Objectives and How the Results Help Inform Asset Risk Decisions The objectives of Study 1 and Study 2 were twofold. First was to illustrate deterministic and stochastic methods that can be used to forecast state revenues.
From page 37...
... Pilot Testing and Results 37   • Monte Carlo: The Monte Carlo method uses statistical parameters for the historical data (mean, standard deviation) and, using a random probability of occurrence per iteration, computes a value for the forecast variable using an inverse probability computation.
From page 38...
... 38 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research Methodology Steps Step 1 Obtain input data. For the pilot, the input data were gasoline and diesel sales volumes, revenues to the Transportation and Transportation Infrastructure Bond (TIB)
From page 39...
... Pilot Testing and Results 39   Step 1: Obtain Input Data Step 1 involved collecting data relating to the state revenue available to VTrans. For context, it was important that the research team understand the various sources of revenue that contribute to the funding available to VTrans and the relative significance of each.
From page 40...
... 40 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research As seen in Table 9-2, the total gasoline tax is 12.10 cents per gallon on gasoline sold. Out of this, 11.345 cents per gallon is available to the Transportation Fund.
From page 41...
... Pilot Testing and Results 41   applicable between FY 2000 and FY 2002 and is no longer in force. Therefore, this source was not included in Studies 1 and 2.
From page 42...
... 42 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research 30% 25% 20% 15% 10% 5% 0% –5% –10% –15% Figure 9-3. Annual rate of change (%)
From page 43...
... Pilot Testing and Results 43   follow the trends consistent with those observed in the preceding and succeeding years. The annual rates of change in FY 2005 and FY 2014 were computed as the average of the rates of change in the corresponding preceding and succeeding years.
From page 44...
... 44 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research in motoring traffic caused by COVID-induced travel restrictions and increases in work from home practices. The partial recovery in the second half of FY 2021 through February 2022 could indicate that although travel by the public has recently increased after the severe drop from pre- pandemic levels, it has not fully recovered.
From page 45...
... Pilot Testing and Results 45   • Estimated recovery as of November 2021: 283 − 276 = 7 million gallons • Percent recovery: 7 ÷ 39 = 18 percent • Assumed recovery as of FY 2022 for pilot testing: 25 percent (increased from 18 percent computed as of November 2021 to an estimated 25 percent as of June 2022 to account for potential continued recovery by fiscal year end) The forecasted gasoline sales volumes were computed for FY 2022 to FY 2032 after assuming that the FY 2022 sales volume would show a partial recovery of 25 percent from the FY 2021 volume.
From page 46...
... 46 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research do not provide the data to establish confidence intervals to account for uncertainty in forecasts. This is a key shortcoming of deterministic forecasts.
From page 47...
... Pilot Testing and Results 47   In the following discussion, study outputs are described for gasoline tax revenues in the following order: • Deterministic • Triple exponential smoothing using Excel • Monte Carlo Study outputs for the remaining sources of revenue for the Transportation Fund and gasoline and diesel assessments for the TIB Fund are included in Appendix E. In each case, the forecast values are shown along with the confidence intervals, followed by a brief discussion highlighting the interpretive component of the study outputs.
From page 48...
... 48 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research the estimates of uncertainty will likely be based on a review of historical data and application of best judgment based on inputs from SMEs (Step 5c)
From page 49...
... Pilot Testing and Results 49   Agencies may consider the approach and the related assumptions after careful consideration and discussions with SMEs. Table 9-8 lists the forecasted gasoline tax revenue to Vermont's Transportation Fund for FY 2022 to FY 2032, assuming a constant annual change in the gasoline sales volume of −0.36 percent and no change in the revenue basis.
From page 50...
... 50 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research illustrate an approach to incorporate uncertainty, which is not inherently present in deterministic forecasting techniques. Step 6a: Calculate Probabilistic Forecasts for Gasoline Sales Tax Revenues Using Triple Exponential Smoothing ETS forecasting options are readily available within the Forecast module under the Data tab in Excel spreadsheets.
From page 51...
... Pilot Testing and Results 51   284 million gallons for FY 2022. However, the confidence interval delivered by the Excel function diverges substantially from the forecast value in the outer years.
From page 52...
... 52 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research The rates of change and the confidence intervals computed for the 500 iterations for each year were used to compute the projected gasoline sales volume for FY 2020 and FY 2021 to estimate the forecasted FY 2021 volume, had COVID not occurred. These data were compared with actual recorded gasoline sales in FY 2021 to compute the estimated reduction in sales attributable to COVID impacts.
From page 53...
... Pilot Testing and Results 53   Projected gasoline sales for the remainder of the forecast period were then computed using the forecasted annual rates of change. The results are shown in Table 9-12.
From page 54...
... 54 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research –1 2% –1 1% –1 0% –9 % –8 % –7 % –6 % –5 % –4 % –3 % –2 % –1 % 0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10 % 11 % 12 % Figure 9-9. Monte Carlo forecast of distribution of annual rate of change (%)
From page 55...
... Pilot Testing and Results 55   Over the forecast period, the Monte Carlo method shows little variability, and the 2032 revenue from gasoline sales to the Transportation Fund is forecasted at approximately $70 million. The 95 percent confidence interval ranges between approximately $67 million and $73 million.
From page 56...
... 56 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research Assumes partial (25%) recovery of COVID impacts by 2022, allowing for continued lower gasoline sales due to sustained residual COVID impacts Figure 9-10.
From page 57...
... Pilot Testing and Results 57   annual decline, and the ETS method forecasting an approximately 0.6 percent average annual decline. The confidence interval for the Monte Carlo method was narrow at approximately 3.8 percent around the forecast values, whereas for the ETS method, it varied between approximately 7 percent and 23 percent.
From page 58...
... 58 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research Fiscal Year Actual Value Lower Confidence Value Forecasted Value Upper Confidence Value 2000 $181.20 2001 $185.90 2002 $198.80 2003 $207.80 2004 $214.60 2005 $209.00 2006 $209.90 2007 $220.90 2008 $223.10 2009 $203.60 2010 $228.10 2011 $236.10 2012 $244.50 2013 $251.20 2014 $274.40 2015 $281.70 2016 $279.60 2017 $285.60 2018 $294.00 2019 $297.60 2020 $278.80 2021 $294.83 $294.83 $294.83 $294.83 2022 $278.23 $304.79 $331.35 2023 $281.82 $308.83 $335.83 2024 $285.51 $312.97 $340.43 2025 $289.29 $317.21 $345.13 2026 $293.16 $321.56 $349.95 2027 $297.13 $326.01 $354.89 2028 $301.19 $330.57 $359.95 2029 $305.36 $335.25 $365.14 2030 $309.62 $340.03 $370.45 2031 $313.99 $344.94 $375.88 2032 $318.47 $349.96 $381.45 Table 9-14. Deterministic forecast of historical and projected VTrans revenues ($, millions)
From page 59...
... Pilot Testing and Results 59   $27 million between the techniques. However, the uncertainty in the FY 2032 forecast using the Monte Carlo method is plus or minus $31 million, while that estimated by the ETS forecast is over or under $51 million.
From page 60...
... 60 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research Fiscal Year Actual Value Lower Confidence Value Forecasted Value Upper Confidence Value 2000 $181.20 2001 $185.90 2002 $198.80 2003 $207.80 2004 $214.60 2005 $209.00 2006 $209.90 2007 $220.90 2008 $223.10 2009 $203.60 2010 $228.10 2011 $236.10 2012 $244.50 2013 $251.20 2014 $274.40 2015 $281.70 2016 $279.60 2017 $285.60 2018 $294.00 2019 $297.60 2020 $278.80 2021 $294.83 $294.83 $294.83 $294.83 2022 $281.61 $310.22 $338.83 2023 $282.88 $314.09 $345.29 2024 $284.36 $317.96 $351.57 2025 $285.96 $321.86 $357.76 2026 $287.63 $325.77 $363.90 2027 $289.36 $329.68 $370.01 2028 $291.11 $333.61 $376.11 2029 $292.89 $337.55 $382.21 2030 $294.68 $341.49 $388.31 2031 $296.47 $345.44 $394.42 2032 $298.26 $349.40 $400.54 Table 9-15. Probabilistic ETS forecast of historical and projected VTrans revenues ($, millions)
From page 61...
... Pilot Testing and Results 61   Many DOT divisions can use the methodology detailed in this pilot to incorporate uncertainties associated with financial forecasting. Depending on the area of application, DOTs may engage various SMEs with the appropriate understanding of the financial data.
From page 62...
... 62 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research Fiscal Year Actual Value Lower Confidence Value Forecasted Value Upper Confidence Value 2000 $138.25 2001 $185.90 2002 $198.80 2003 $207.80 2004 $214.60 2005 $209.00 2006 $209.90 2007 $220.90 2008 $223.10 2009 $203.60 2010 $228.10 2011 $236.10 2012 $244.50 2013 $251.20 2014 $274.40 2015 $281.70 2016 $279.60 2017 $285.60 2018 $294.00 2019 $297.60 2020 $278.80 2021 $294.83 $294.83 $294.83 $294.83 2022 $278.37 $305.06 $330.92 2023 $282.90 $309.32 $336.19 2024 $285.77 $313.70 $340.21 2025 $290.04 $318.03 $345.23 2026 $295.29 $322.45 $349.38 2027 $298.18 $327.24 $354.67 2028 $302.93 $332.30 $360.75 2029 $306.98 $337.21 $368.24 2030 $310.27 $342.39 $372.99 2031 $317.46 $347.41 $377.97 2032 $319.22 $352.04 $382.14 Table 9-16. Probabilistic Monte Carlo forecast of historical and projected VTrans revenues ($, millions)
From page 63...
... Pilot Testing and Results 63   Figure 9-14. Probabilistic Monte Carlo forecast of total VTrans revenues ($, millions)
From page 64...
... 64 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research The methodologies can be applied to forecast costs of essential commodities, such as steel, asphalt, and concrete, that impact infrastructure projects planned for the 10-year TAMP. Such estimates can then be used to forecast future costs.
From page 65...
... Pilot Testing and Results 65   optimization analysis, this function is used in a management system to maximize a selected value -- the objective -- under a set of constraints.) Run analysis to identify an optimal structures work program, including risk.
From page 66...
... 66 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research values for use in calculations. Relative weighting gives each selected subcomponent a weighting that totals 100.
From page 67...
... Pilot Testing and Results 67   scenarios. The detailed use of these formulae is described under Step 13 in Appendix F.
From page 68...
... 68 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research The system looks at the consequences of closure and structure weight assigned and generates a change in the risk value based on the projects selected by the optimization. Different types of projects have different effects on the risk subcomponents.
From page 69...
... Pilot Testing and Results 69   In the pilot test scenario with $125 million funding, the BMS suggested the following projects that affect risk: • 10 bridge replacements with widening • 4 bridge replacements without widening • 25 deck replacements with widening • 15 deck replacements without widening • 68 reinforced concrete box (RCB) replacements The scenario with $250 million funding suggested these projects that affect risk: • 10 bridge replacements with widening • 4 bridge replacements without widening • 34 deck replacements with widening • 22 deck replacements without widening • 135 RCB replacements Figure 9-16 shows the risk index improving (i.e., the risk utility increasing)
From page 70...
... 70 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research Although seemingly simple, the trends shown are the result of considerable modeling and benefit–cost optimization automatically carried out in the BMS analysis. The output also shows how risk was fully incorporated into the main analysis already carried out in BMSs.
From page 71...
... Pilot Testing and Results 71   Based on the pilot, an agency would typically need to commit some resource hours from the in-house personnel who configure and run the BMS. The configuration requires access to the BMS and the ability to run analyses and generate the resulting reports.
From page 72...
... 72 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research 9.3.3 Methodology Used in Conducting the Pilot The methodology steps describe how the analysis was conducted using DelDOT's PMS. The eight main steps of the methodology are shown in Table 9-19 and summarized in this section.
From page 73...
... Pilot Testing and Results 73   So ur ce Fl oo d Le ve ls St or m S ur ge Ra in fa ll O ve r� lo w in g Ri ve rs /S tr ea m s H ig h Ti de s Se a Le ve lR is e Cl im at e Ch an ge As so ci at ed P ro ba bi lit ie s H is to ri ca l I nf or m at io n Fu tu re P ro je ct io ns Ap pl ic ab le L oc at io ns D at a D ow nl oa d FloodFactor17 Y Y Y Y Y Y Y Y Y Y National Potentially NOAA Sea Level Rise Viewer18 Y Y Y N Y Y National Y Climate Central Water Level19 Y N N N N Y N N Y National For a price Climate Central Year20 N Y N N Y Y Y Y N Y National Climate Central Risk Zone Map21 Y Y N N Y Y Y Y N Y National Hazus22 Y Y N N N N N N N N National Y FEMA National Flood Hazard Layer Viewer23 Y N Y National Y National Storm Surge Hazard Maps24 Y Y Y N Y N N N N Y Coasts National Potentially Coastal Emergency Risk Assessment25 Y Y Y Y N Y Y National N FEMA Flood Map Service Center26 Y Y Y Y Y Y National Y DNREC Flood Planning Tool27 Y Y N Delaware Y University of Delaware Water Resources Center28 Y Y N Y Delaware Y Delaware Flood Risk Adaptation Map29 Y Y N N N Y N Y N Y Delaware Y Coastal Inundation Maps for Delaware30 Y N N N N Y N N N N Delaware Y FirstMap31 N Delaware Y DelDOT Gateway32 N Delaware Y For a price For a price N���: Blank cells indicate uncertainty about whether the data type was included or considered. NOAA = National Oceanic and Atmospheric Administration.
From page 74...
... 74 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research To ensure that the study methodology could be applied to other states, nationally available data were used for analysis. As such, the FEMA Flood Map Service Center listed in Table 9-20 was selected as the source for national flood data.
From page 75...
... Pilot Testing and Results 75   ID Spreadsheet Category Formula Sources and Assumptions 1 Name From PMS Network Master Source: DelDOT's network master in their PMS. 2 County From PMS Network Master Source: DelDOT's network master in their PMS.
From page 76...
... 76 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research meaning projects were selected to maximize overall network condition over time. The scenario included a list of either committed projects or scheduled projects for which funding was committed, as well as funding constraints for districts and work types for the remaining project selection.
From page 77...
... Pilot Testing and Results 77   scenario resulted in the selection of one risk mitigation reconstruction project in the nal year of the 15-year analysis period. – 0.5 Risk Scenario: In this scenario, the risk objective and condition objective were both weighted at 0.5.
From page 78...
... 78 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research There is a notable difference between the baseline and 0.25 risk scenarios and the 0.5 risk scenario starting in 2031, when the average OPC begins to drop more significantly through 2036 for the 0.5 risk scenario. This is attributable to the selection of 16 risk-mitigating projects that have a positive effect on the total risk but are not as beneficial to the overall condition as the projects in the original work plan.
From page 79...
... Pilot Testing and Results 79   9.3.5 Participating DOT Organizational Unit(s) This pilot was conducted with the involvement of the DelDOT pavement management team, PMS technicians, and GIS specialists.
From page 80...
... 80 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research managers could then develop recommendations based on the results of the assessment of networkwide flooding risk levels and trends that can be expected for specific budgets. 9.3.7 Challenges in Pilot Study Setup The setup of the pilot study involved a significant amount of troubleshooting within the PMS as well as difficulty with access to the system caused by technical issues.
From page 81...
... Pilot Testing and Results 81   • Threats: Variation in inflation rate; unplanned changes to available funding levels • Consequences: Impacts to forecasted condition metrics • Implementation Effort: Defined high, expected, and low values of chosen input values representing threats; ran multiple analyses to identify optimum strategies and forecast resulting metrics for high, expected, and low scenarios; and analyzed and summarized resulting metric projections 9.4.1 Pilot Objective and How the Results Help Inform Asset Risk Decisions The objective of this pilot study was to demonstrate a real-world example of the analysis of pavement program-level risk by forecasting condition based on high, expected, and low extents of program-level variables using existing tools. An expected envelope of predicted average network condition can be created to better inform decision makers about the risks to the network.
From page 82...
... 82 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research The following three scenarios were set up for analysis within the system: 1. The best-case scenario, in which the most optimistic values for construction inflation rate (3.55 percent)
From page 83...
... Pilot Testing and Results 83   represents the overall worst-case scenario in which the construction inflation rate is high and there has been a 30 percent decrease in funding. The worst-case scenario is expected to pose the highest risk to the overall pavement network condition, as this would lead to a significant reduction in treatments applied to pavements.
From page 84...
... 84 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research 0 20 40 60 80 100 O CI Avg OCI - Worst Case Avg OCI - Expected Avg OCI - Best Case Figure 9-21. Projected OCI for best-case, expected, and worst-case scenarios for funding levels and ination rates, 2021–2040.
From page 85...
... Pilot Testing and Results 85   scenarios after 2030 was partially explained by all three inflation rates being higher than ITD's typically assumed 2 percent inflation rate. Because the changes in construction costs specific to ITD's pavement projects were used to determine the inflation rates, they were more applicable for these scenarios than the 2 percent rate ITD usually uses in analysis.
From page 86...
... 86 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research the level of detail desired, an agency implementing this method would need resources and tools to determine the variation levels to be used to set up scenarios. When setting up and running scenarios, the agency will need to commit some resource hours from the technical personnel who typically manage the PMS.
From page 87...
... Pilot Testing and Results 87   to other risks. In addition, the guidance included an approach to evaluate the likelihood of climate change risks so that they can be evaluated relative to other risks.
From page 88...
... 88 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research The core teams from MDOT and MnDOT filled out one worksheet per agency with their collective feedback. MnDOT held an additional working session with its TAMP Advisory Group to vet the guidance, with a wider sampling of staff using the worksheet prompts to gather additional feedback.
From page 89...
... Pilot Testing and Results 89   • Are the definitions of vulnerability and risk assessment terminology clear? • Is the relationship between vulnerability and risk assessment terms clear?
From page 90...
... 90 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research Step 6: Revising the Guidance The research team updated the guidance based on the feedback received from the two pilot DOTs to improve the accessibility and usability of the guidance. The final guidance can be found in Appendix L.
From page 91...
... Pilot Testing and Results 91   walked through this process conceptually, both agencies felt that, with their suggested improvements listed in Table 9-28, they would be able to produce useful climate risk information to then integrate into their asset management processes. 9.5.5 Participating DOT Organizational Unit(s)
From page 92...
... 92 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research 9.5.6 Who in a DOT Could Use the Pilot Results and How Study 9 is intended to inform asset management planning. MDOT would like to use the guidance to expand its next TAMP to include a broader range of hazards, including climate hazards and network-scale impacts.
From page 93...
... Pilot Testing and Results 93   MDOT requested an additional climate data resource be included in the final guidance to provide data on fluctuating Great Lake water levels. Following the DOT's feedback, an additional resource was added to the table of climate data sources in the guidance.
From page 94...
... 94 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research 3. A summary description of the condition of NHS pavements and bridges 4.
From page 95...
... Pilot Testing and Results 95   network-wide performance. These large structures present a disproportional risk to both condition and performance targets.
From page 96...
... 96 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research 1 "IMMINENT" FAILURE CONDITION -- major deterioration or section loss present in critical structural components or obvious vertical or horizontal movement affecting structure stability. Bridge is closed to traffic but corrective action may put back in light service 0 FAILED CONDITION -- Out of service -- beyond corrective action.
From page 97...
... Pilot Testing and Results 97   Table 9-31 shows the summary of the 2020 Minnesota NBI data. The percentage of NHS bridges rated poor is 2.2 percent and the percentage of bridge deck area rated poor is 3.2 percent.
From page 98...
... NHS Bridges NHS Culverts All NHS Structures Condition Bridges (No.) Bridges (Area)
From page 99...
... Pilot Testing and Results 99   In addition, the pilot suggested that MnDOT consider selecting one or more of the following targets to address the 10X at-risk bridges and refine them for inclusion in the next TAMP: • MnDOT will repair, rehabilitate, and/or reconstruct the 10X bridges and bring their substructures, superstructures, and decks to good or fair condition within the next 30 years. • MnDOT will continue to inspect 10X bridges that are in poor condition more frequently until they are brought to a state of good repair.
From page 100...
... All Bridges All Culverts All Bridges and Culverts Condition Bridges (No.) Bridges (Area)
From page 101...
... Pilot Testing and Results 101   59.5 percent, and 3.2 percent of all NHS structures are good, fair, and poor, respectively. It also shows that the 3.2 percent poor deck area on NHS structures is attributable to 31 bridges and 11 culverts.
From page 102...
... 102 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research substructures, each structure would need engineering analysis to determine how to prevent the substructure from deteriorating to a poor condition. The need for such analysis could justify developing long-term bridge management plans that incorporate life cycle planning strategies for each structure as a TAMP objective.
From page 103...
... Pilot Testing and Results 103   As defined by 23 CFR 515.5, "Performance gap means the gaps between the current asset conditions and State DOT targets for asset condition, and the gaps in system performance effectiveness that are best addressed by improving the physical assets." The performance gap will depend on the targets established for the assets for the next 10 years of the TAMP. As more 10X bridges in poor or worse condition are treated, the overall percentage of poor bridges will decrease.
From page 104...
... 104 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research 3. Prioritize them.
From page 105...
... Pilot Testing and Results 105   federal requirements to meet NHS bridge and Interstate pavement targets. In addition, DOTs include the investment strategies and the funding needed to meet all state performance objectives and targets.
From page 106...
... 106 Risk Assessment Techniques for Transportation Asset Management: Conduct of Research 9.6.8 Resources Needed by a DOT to Implement the Study This study is timely and not difficult for DOTs to include in their TAMPs. The pilot was conducted using MnDOT's published NBI data, so no additional DOT resources were needed.

Key Terms



This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.