HERS-ST Highway Economic Requirements System - State Version: User's Guide
Chapter 7 Working with Input Data (Control, Parameter, Outputs)
This chapter addresses the internal Control, Parameter, and Output settings that HERS-ST uses during an analysis. The information in this chapter describes these settings and the preparation needed for use in HERS-ST.
The HERS-ST software includes default values for all of the Control and Parameter inputs used by the model. The default values are those that were used in the investment analyses of the FHWA Conditions and Performance Report to Congress. When HERS-ST processes an analysis, the Control, Parameter, and Output settings provide the following information:
|Control||Analysis objective, method, cost units, weight, traffic, and other analytical factors.|
|Parameter||Improvement costs, deficiency levels, and numerous other parameters that affect the analysis models.|
|Outputs||Data capture options for the System Conditions, Section Conditions, and Improvement Statistics.|
Setting the control data enables you to specify the analysis objective, method, cost units, output information, and other settings to control the analysis. A Workset can have any number of control settings, although only one set can be active at a time. The active control setting is indicated by an option button displayed to the left of the control settings label in the Workset tree.
You can edit the control settings using the standard interview, which provides a logical organization of pages to display the most common settings. Of course, you also may choose to accept the default settings for the analysis.
To make a Control active, you must select it using the option button displayed to the left of the control setting in the Workset tree.
The control settings interview provides the means to edit the HERS-ST control settings. The control interview is displayed by double-clicking the control settings branch in the Workset tree (Figure 7-1), or selecting the Display item in its popup menu.
Figure 7-1. Workset Tree (Settings).
On the General Information page of the control settings interview you enter a name and description for the settings (Figure 7-2). The last user to modify the settings and a corresponding timestamp are also displayed. You will also enter a scenario name and description for these settings.
Figure 7-2. Control Settings (General).
The control settings are not applied until the interview is finished. You may click the Apply button at any point in the interview process. If the name of the set of control settings is changed, you will be asked if you want to create a new set of control settings or rename the existing.
The Objective page (Figure 7-3) settings determine the type and method of the analysis. You can select from the four analysis types and select how to partition the highway system. Depending on which options are selected, the next two pages may not apply to your scenario.
Chapter 3 describes each of the four types of analysis objectives in more detail.
Figure 7-3. Control Settings (Objective).
If you select the objective to maximize benefits as constrained by funds, you will see the Available Funds page (Figure 7-4). This page shows the amount of funding available for each funding period by functional classification for up to four funding periods.
When a field is left blank, the value for the previous funding period is used.
Figure 7-4. Control Settings (Available Funds).
If you select the objective to minimize improvement costs as constrained by performance and you have not chosen to maintain the current conditions, you will see the Performance Goals page (Figure 7-5). This page shows the performance goal for each funding period by functional classification for up to four funding periods. The values are entered in dollars or incidents per vehicle-mile or in maintenance costs per mile depending on the type of performance goal selected.
When a field is left blank, the value for the previous funding period is used.
Figure 7-5. Control Settings (Performance Goals).
If you selected the performance constrained analysis objective, the constraint weights page (Figure 7-6) is displayed. The information is organized by cost components with each component having an entry for each of the nine functional classes distinguished by HERS-ST. The actual cost components listed are those appropriate for the specified type of goal.
Figure 7-6. Control Settings (Constraint Weights).
The constraint weights are used to establish a relative weight that each component contributes to the performance goal. Setting an entry to zero removes that cost component and functional class combination from the performance goal. To evenly weight each cost component, set all the entries to one. All entries must between the values of zero to one.
On the Other Settings page (Figure 7-7) you set a variety of miscellaneous options including the Funding Period configuration and other settings that are commonly modified.
Figure 7-7. Control Settings (Other Settings).
- Discount Rate. Annual rate used to discount future benefits and costs.
- Length of Funding Period. Identifies the duration of a single funding period in years. HERS-ST uses the funding period as the length of the benefit-cost analysis period to base the decision of whether to improve a highway section. With a shorter period, the number of improvements meeting the benefit-cost criteria drops.
- Number of Funding Periods. The number of funding periods to be analyzed. In HERS-ST, funding and performance constraints are limited to four periods. When processing more than four periods, HERS will use the entries for the fourth funding period for all subsequent periods.
- PSR for Unpaved Sections. This value is used as the PSR for all unpaved sections.
- AADT Calculation Method. Type of Average Annual Daily Traffic (AADT) calculation to perform. This field identifies which of three types of algorithms to use in forecasting future baseline traffic volume.
- Upper Limit for AADT / Capacity Ratio. This field establishes the maximum AADT/Capacity ratio that a highway section can have. HERS will use this value, and adjust the capacity accordingly, on sections whose AADT/Capacity ratio exceeds this value.
- Maximum Annual Traffic Growth Rate. This field identifies the maximum percentage of annual traffic growth rate that a highway section can have.
The Units page collects settings for the units of measurement used in the analysis (Figure 7-8). The units of cost entries allow you to scale output cost data and the units of VMT allow you to scale the calculated vehicle miles traveled.
Figure 7-8. Control Settings (Units).
Setting the parameter data enables you to specify significant information, such as pavement specifications, improvement costs, and deficiency thresholds for the HERS-ST analysis. A Workset can have any number of parameter settings, although only one can be active at a time. The active set of parameter settings is indicated by an option button displayed to the left of the parameter settings label in the Workset tree.
You can edit the parameter data using the standard interview, which provides a logical organization of pages to display the most common settings. Of course, you also may choose to accept the default settings for the analysis.
To make a Parameter active, you must select it using the option button displayed to the left of the parameter setting in the Workset tree.
The parameter settings interview provides the means to edit the HERS-ST parameter settings. The parameter interview is displayed by double-clicking the parameter settings branch in the Workset tree (Figure 7-1), or selecting the Display item in its popup menu.
On the General Information page of the parameter settings interview, you enter a name and description for the settings (Figure 7-9). The last user to modify the settings and a corresponding timestamp are also displayed.
Figure 7-9. Parameter Settings (General).
The parameter settings are not applied until the interview is finished. You may click the Apply button at any point in the interview process. If the name of the set of parameter settings is changed, you will be asked if you want to create a new set of parameter settings or rename the existing set.
The Improvement Costs page (Figure 7-10) is used to specify the cost of improving each functional class in different urban areas and rural terrains. Improvement costs are specified for resurfacing and reconstruction with or without lane widening, shoulder improvements, the cost of adding lanes, and alignment improvements. These costs are entered for each urban functional class in small and large urbanized areas and for each rural class on flat, rolling, and mountainous terrains.
Figure 7-10. Parameter Settings (Improvement Costs).
The improvement costs are adjusted for each highway section based on the Local Cost Factor (LCF) field in the highway data.
The Deficiency Levels page (Figure 7-11) displays threshold settings to determine when a section is considered deficient.
For the PSR thresholds, larger values represent better conditions, so sections that measure less than the specified threshold are considered deficient. The opposite is true for VCR thresholds.
The thresholds are organized for each functional classification and subdivided by Average Annual Daily Traffic (AADT) volume. The rural classes are further subdivided into the three terrain types of Flat, Rolling and Mountainous. Three sets of thresholds are available.
- Deficiency Levels. The deficiency level identifies deficiencies that warrant analysis. Setting the deficiency level close to the design standard will cause HERS-ST to analyze improvements that would be extremely unlikely to be cost-beneficial and will greatly increase computational time.
- User Thresholds. The user thresholds allow you to create custom trigger points to create tailored views of the highway system. Information about the highway sections that fall below the user-defined thresholds are written to the System Conditions mileage and VMT deficiency tables (see Chapter 9).
- Reconstruction Levels. The reconstruction level represents the level at which resurfacing the pavement is no longer an option and reconstruction is the only means to restore the pavement. Only PSR has a reconstruction level.
Figure 7-11. Parameter Settings (Deficiency Levels).
The price index values (Figure 7-12) represent the price index relative to the reference year for the listed items. The reference year is the year to which costs for each item apply. The price index allows you to modify the costs for each item by a percentage to adjust values to the current year.
Figure 7-12. Parameter Settings (Price Index).
The Pavement Factors page (Figure 7-13) provides various factors that affect the deterioration rate and maximum life of both flexible and rigid pavement.
- PDR Adjustment Factors. These factors adjust the Pavement Deterioration Rate (PDR) for each functional class.
- Life Expectancy. These values specify the life expectancy of flexible and rigid pavement types.
Figure 7-13. Parameter Settings (Pavement Factors).
On the Other Settings page (Figure 7-14) you set a variety of miscellaneous options.
- Design Period. This field specifies the design life of the pavement and is used in estimating the future traffic volume for the purpose of determining lane requirements. HERS-ST projects the AADT growth from the year an improvement is implemented through the life of the design period.
- Maximum Pavement Deterioration Rate. This field limits the amount that the PSR can be decreased in a year.
Figure 7-14. Parameter Settings (Other Settings).
To make an Output active, you must select it using the option button displayed to the left of the output setting in the Workset tree.
The output settings enable you to specify what information you want HERS-ST to capture from its analysis. A Workset can have zero or more output settings defined, although only one can be active at a time. The active output setting is indicated by an option button displayed to the left of its label in the Workset tree.
The output settings interface provides the means to edit the HERS-ST output settings. The interface is displayed by double-clicking the output settings branch in the Workset tree (Figure 7-1), or selecting the Display item in its popup menu.
On the General Information page of the output settings interface you enter a name and description for the settings (Figure 7-15). The last user to modify the settings and a corresponding timestamp are also displayed.
Figure 7-15. Output Settings (General).
The Improvement Statistics page (Figure 7-16) provides a means to select the improvement types you want to capture and the statistical categories you are interested in. Place a check mark next to the items that you wish to capture. You also have the option to disable the data capture for this type of system data.
Some of the statistical categories have sub-categories with them. These are displayed hierarchically beneath their parent branch in the categories tree. You can capture all of the sub-categories by placing a check mark next to the top-level branch in the tree, or you can capture individual sub-categories.
Figure 7-16. Output Settings (Improvement Statistics).
The System Conditions page (Figure 7-17) provides a means to select the system conditions information you are interested in. The system condition categories are displayed in two hierarchical trees, one for condition categories and the other for deficiency categories. Some branches also contain sub-categories. You can select all or some of the sub-categories as needed. You also have the option to disable the data capture for this entire type of data.
Figure 7-17. Output Settings (System Conditions).
The Section Conditions page (Figure 7-18) provides a means to select the section conditions information you are interested in. A list of data fields is provided in a hierarchal tree.
Unlike the other data types, the section conditions options determine if data are captured and placed in the individual data fields of each section record; the overall number of records (one for each highway section) is not affected.
Three options are provided to control when section conditions information is captured as follows:
- Include the Initial Section Conditions. Disable this option to prevent HERSST from capturing the initial state of the highway system before the analysis is performed. This data can be considered redundant since it mirrors the information in the highway data; however you may want to capture it for comparison analysis on changes that occur in the highway system.
- Only include Section Conditions data with a Recommended Improvement. This option is useful to capture information about the conditions of only those highway sections that have had an improvement. Since many highway sections will not need an improvement within a funding period, the option can greatly reduce the number of records captured in the database.
- Only capture the Section Conditions at the end of the last Funding Period. This option will ignore the section conditions that are reported during the analysis period and will only capture the section conditions at the end of the last funding period.
Figure 7-18. Output Settings (Section Conditions).
1. Double-click Control Settings in the workset tree.
2. Double-click the new control settings branch in the workset tree or select the Display item from its popup menu. The Control Settings window displays.
3. Enter a name for the Control Settings.
5. Click Next. Specify the analysis objective options and whether you want to include any improvement overrides.
6. Click Next. Depending on your objective, enter the available funds or performance goals for the analysis.
7. Click Next. If necessary, accept or edit the constraint weights.
8. Click Next. Accept or edit your optional settings.
9. Click Next. Set the units of measurement to be used in the analysis.
10. Click Apply.
- Double-click Parameter Settings in the workset tree.
- Double-click the new Parameter Settings branch in the workset tree or select the Display item from its popup menu. The Parameter Settings window displays.
- Enter a name for the Parameter Settings.
- Click Next. Accept or enter the improvement costs.
- Click Next. Click on the User Thresholds option button and accept or enter the deficiency levels for the deficiency types.
- Click Next. Accept or enter the price index for each index type based on its reference year, or modify the reference year to correspond to the price index.
- Click Next. Accept or edit the pavement factors.
- Click Next. Accept or edit your optional settings.
- Click Apply.
- Double-click Output Settings in the workset tree.
- Double-click the new Output Settings branch in the workset tree or select the Display item from its popup menu. The Output Settings window displays.
- Enter a name for the Output Settings.
- Click on the Improvement Statistics tab. Accept or enter the default data capture options for the improvement statistics.
- Click on the System Conditions tab. Accept or enter the default data capture options for the system conditions.
- Click on the Section Conditions tab. Accept or enter the default data capture options for the section conditions.
- Close the window.