Frequently Asked Questions

This page is a collection of the most common questions and answers regarding FREEVAL-PA.This collection will be updated as new questions arise. If you have a new question that is not answered here or in the FREEVAL-PA Manual, please ask the question in the Discussion Forums.

• Installation and Software Support
  • How do I install the FREEVAL-PA software?

    The FREEVAL-PA User Guide provides step-by-step instructions and screenshots regarding the installation process. A quick reference guide is provided below:

    1. Click here to access the Documents & Downloads" webpage. 
    2. Once on the "Documents & Downloads" page find the section labeled "Freeval-PA Installer Package File(.MSI)
    3. Click to expand the label to expand the section. 
    4. Click "FREEVAL-PA Version 1.02” (*Note - Version 1.02 is the current version but is subject to change)
    5. On "Download Details" click the button labeled, "Click to Download" (*Note download may take several minutes, please let the download complete prior to moving to step 6.)
    6. Navigate to the location of the downloaded zip file and extract all files.
    7. Once the Windows Installer File has been extracted, double-click the file to launch a guided installation wizard.
       (***Note - Admin privileges will be required to complete this step.***)
    8. If desired specify an install location, but in general the default location (C:\Program Files\) should suffice. 
    9. Once the installation wizard has finished, the program is ready to launch.
    10. The FREEVAL-PA installer will automatically create a desktop shortcut and a start menu entry for the FREEVAL-PA software.
  • Will the FREEVAL-PA Software be updated in the future?

    PennDOT will periodically release updates to the FREEVAL-PA software, which will be posted to this website. Minor updates and bug fixes will be denoted with a “.01” version increment (e.g. Version 1.02, 1.03), the inclusion of new modules and procedures with a “.1” version increment (e.g. Version 1.1, 1.2), and major updates of the software with a “1.0” version increment (e.g. Version 1.0, Version 2.0). Each update will be accompanied by release notes to describe what is contained in the update.

  • Does FREEVAL-PA have any licensing restrictions?

    FREEVAL-PA is distributed freely for use within the state of Pennsylvania, and specifically for the support of PennDOT projects. The software is free to use but should not be expanded or modified without written permission from PennDOT.

  • Who do I contact for software support?

    For software support, please submit a discussion question through the website, and PennDOT or the developer team will respond.

  • How do I update Freeval software?

    To update the FREEVAL-PA software, the old version should be removed using the installer file, or the ‘add/remove’ programs feature within Windows. Then the new version of FREEVAL-PA should be downloaded and installed using the procedure described in the user guide.

• Analysis Overview and Use Cases
  • When do I use Planning-Level features?

    The planning-level modules in FREEVAL-PA are intended to allow for quick screening of scenarios, including for work zone lane closures. The planning analysis provides results very quickly, without the need for detailed inputs and calibration. It is a quick estimation method to evaluate the volume-to-capacity ratio (v/c) for different scenarios. But it will not provide detailed delay and queuing performance measures like the detailed analysis. Potential use cases for the planning-level features are high-level screening of lane closure impacts for a given segment, evaluating potential work hours by time-of-day, and exploring impacts of traffic growth or diversion on the v/c patterns.

  • When do I complete a Detailed Analysis?

    The detailed analysis should be used whenever more detailed performance measures are desired (queue lengths, delays and travel time, LOS), and when an extended facility with different segment geometries (merge, diverge, weaving) is being evaluated.

  • What is the PennDOT Segmentation Database and when should I use it?

    The geometries for all limited access facilities maintained by PennDOT (including Interstates, and limited access US, and State roads in Pennsylvania) have been mapped and are saved in PennDOT's Segmentation Database. These pre-mapped roadway segments can be used as a base for FREEVAL project evaluations. The database contains the Highway Capacity Manual (HCM) segment type, number of lanes, acceleration and deceleration lane lengths, weaving geometry details, grade information, and truck percentages. The database is intended to streamline a FREEVAL-PA detailed analysis, but the user is still required to confirm all inputs and calibrate a model to assure the entries are correct.

  • Are Planning-Level and Detailed-Analysis features connected in any way?

    The planning-level analysis can be conducted independently of the detailed analysis. If a planning-level screening indicates that further analysis is needed, the user should start a detailed analysis. In this case the two are not connected, and the user does not need to specify a facility or use the segmentation database.

    The planning-level features can also be accessed from within the detailed analysis modules once a facility has been defined. In this case, the planning-level analysis will pull features from the detailed inputs, can be used to provide high-level screen of individual segments, or to conduct a lane reservation screening analysis for all segments within a facility. These use cases are described in the planning-level training module of the FREEVAL-PA introductory course.

  • How do I conduct a future build analysis?

    The best way to complete a future build analysis is to "save as" a base FREEVAL-PA File and modify it as a new FREEVAL-PA file. The workflow is to complete a FREEVAL-PA analysis for existing conditions (base year no-build), calibrate the facility, and complete the base year no-build analysis, including generating reports. The user can then save additional copies of the base file for future alternatives (future no-build, future build, etc.). This will result in multiple FREEVAL-PA files that can be stored in the same folder, and each can be used to generate a standalone report for each that are then compared. This workflow is consistent with other software tools.

    Refer to Section V - Future Alternatives of the user manual for more guidance for some of the more common alternatives, including (a) traditional widening or geometric improvements, (b) interchange additions/modifications, and (c) TSMO strategy evaluation.

  • How do I complete a Detailed Analysis?

    To complete a detailed analysis, first update the existing Geometric Inputs, Capacity, and Demand (on the home screen). Then move to the next tab, "Detailed Analysis Calibration" and calibrate the model using existing field data.  Then explore the facility segments and analyze alternative scenarios using the "Detailed Segment Explorer" tab or the "Detailed Scenario" tab. 

  • What is the difference between a ‘scenario’ analysis and an ‘alternatives’ analysis in FREEVAL-PA?

    A ‘scenario analysis’ in FREEVAL-PA is conducted within a single FREEVAL-PA file and is generally limited to minor changes for the scenario (e.g. capacity of one or more segments). The scenario analysis is designed to evaluate the impacts of work zones, incidents, or weather events on an existing facility – WITHOUT CHANGING the underlying facility geometry or the input demand pattern. The scenario analysis module allows for direct comparison of performance measures (e.g. delays, travel times, queue lengths) within one FREEVAL-PA file, including the creation of a scenario comparison report.

    An ‘alternatives analysis’ is conducted in different FREEVAL-PA files, much like would be done in other traffic operations or simulation software. In this case, the users save the FREEVAL-PA file under a different file name to make modifications. Alternatives allow the user to change the underlying geometry of the facility (e.g. adding a lane, adding or modifying an interchange, adding a part-time shoulder user system, etc.), the underlying demand (e.g. overall demand with future growth, changing demand pattern by time of day, peak spreading strategies, etc.), or a combination of the two. Any comparison between scenarios in done outside of FREEVAL-PA by either comparing the two output reports or comparing results in a spreadsheet

    PRO TIP: All FREEVAL-PA input and output tables have copy and paste capability!

• Changing Project of Facility Limits
  • How do I edit geometry?

    The geometry of a facility can be edited by clicking on the Geometric Inputs button in the Project Info tab of the FREEVAL-PA project home dashboard.  When the base facility for a work zone or standard operational analysis is generated from the PennDOT Segmentation Database, the user will only need to edit the geometry in rare cases.  However, when analyzing a custom facility or build conditions for an alternative, the user will need to make use of these inputs to change facility attributes such as HCM segment type, segment length, number of lanes and terrain type.

  • How do I edit segments?

    The length and number of segments can be edited by clicking on the Geometric Inputs button in the Project Info tab of the FREEVAL-PA project home dashboard and clicking Add Segment, Delete Segment, or Insert Segment as desired. When the base facility for a work zone or standard operational analysis is generated from the PennDOT Segmentation Database, the user will only need to add segments in rare cases, including:

    • to better understand the impacts of congestion in a long, basic segment
    • when considering the development of a new interchange

    However, when analyzing a custom facility or build conditions, the user will need to make use of these inputs to develop the facility.

  • How do I change the number of analysis periods?

    FREEVAL-PA allows up to a 24-hour analysis in one single evaluation, by evaluating 96 individual time periods. The 24-hour analysis is the default in FREEVAL-PA, and performance measures can be extracted for just a subset of time periods to arrive at for example AM Peak Hour or PM Peak Hour results. The 24-hour time period can also be shifted to start at a time other than midnight (the default) to for example allow for the evaluation of nighttime construction activities (evaluating when to close and when to re-open lanes in a single file).

    To change the number of analysis periods, the user should select the “Change Project Limits” button on the Project Information tab of FREEVAL-PA.

  • How to save or share a FREEVAL-PA file?

    FREEVAL-PA has the ability save any detailed analysis as a .seed file. This file stores all inputs of the detailed analysis and can be emailed, shared, and opened on other computers to generate the same results. The “save as” feature can be used to change the file name for different alternatives to be evaluated.

    Since the planning-level analysis is a very quick assessment with minimal inputs, no standalone load/save functionality is provided. The best way to “save” a planning analysis is through a screenshot of the results.

    Pro Tip: Under the “settings” menu, the user can specify the default folder location to open and save FREEVAL-PA files.

• Methodology and Background Information
  • What is the HCM freeway facilities method?

    The Highway Capacity Manual (HCM) freeway facility method allows for computation of the HCM capacity and Level of Service (LOS) for a series of contiguous freeway segments, including basic, merge, diverge, and weaving segments. The freeway facilities method was first introduced in the HCM2000 and has been continuously developed since that time to include additional functionality. For an undersaturated freeway facility (all segment demands are below capacity for all time periods) the method conducts the segment-specific HCM calculations and aggregates the performance measures across time and space. For oversaturated facilities (at least one segment with demand exceeding capacity), the method tracks the queue accumulation and dissipation over time and space much like a microsimulation tool would.

    The main characteristics of the HCM freeway facilities methodology (relative to the individual freeway segment methods) are:

    • Combines the analysis of multiple segments along an extended length of a freeway (ideally less than 15 miles in length)
    • Performs the operations over multiple (15 min) analysis periods
    • Incorporates segment methodologies for basic segments, merge/diverge segments, and weaving segments
    • Considers oversaturated conditions with queue spillback
  • What types of analyses can the HCM method be used for?

    The types of analyses the HCM method can be used for includes:

    • Alternatives Analysis, including widening, geometric improvements, interchange modifications, etc.
    • Work Zone Analyses, including lane closures, shoulder closures, diversion, etc.
    • Weather or Incident Analyses
    • Transportation System Management and Operations (TSMO) strategies, including part-time shoulder use (TSMO), ramp metering, variable speed limits, etc.
    • Whole-year reliability analysis considering changes in demand and capacity due to recurring and non-recurring sources of congestion
    • Special studies, including evacuation modeling or other custom applications
• Model Inputs and Calibration
  • When do I calibrate a facility?

    A facility should always be calibrated when performing a Detailed Analysis. To calibrate a FREEVAL model, the following six steps should be followed:

    1. Obtain calibration field data. The best source of field data are probe-based speed and travel time data from PennDOT’s RITIS portal. To calibrate FREEVAL, the user should ideally have a 24-hour profile of end-to-end facility travel times, as well as speed observations for each segment and time period across the facility. The calibration data should be for the ‘average’ day that the FREEVAL-PA base file represents, not including special event traffic, work zones, incidents, or weather impacts – unless the particular FREEVAL file is intended to be calibrated for those conditions.
    2. Calibrate Free-Flow Speed (FFS) Adjustment Factors (SAF). The user should look at uncongested time periods (i.e. late at night) and get the segment speeds. For any segments where the FFS is significantly less than the free-flow speed used, adjust it down by a factor of SAF=observed/theoretical ... for example SAF=50/55 mi/h = 0.91. This step should be performed first, given that FFS also impacts capacity. All segments should have a base free-flow speed on the order of speed limit + 5 mi/h (e.g. 60 if posted at 55), which are then calibrated down using segment-specific SAFs. While FREEVAL-PA allows the SAF to change by time of day, the same SAF should generally applied to the entire 24-hour period for a given segment. Exceptions include special circumstances, such as the FFS dropping during eastbound morning commute hours due to sun glare.
    3. Apply "Seed Capacity Adjustment Factors (CAF)" for bottleneck segments. The PennDOT default capacities available in FREEVAL-PA are a good initial step to get capacities for merge, diverge, and weaving bottlenecks to more realistic values. But capacities for some bottlenecks may be even less than the PennDOT defaults, particularly for older freeway segments. If available, sensor data can be used to field-measure capacities following the HCM procedure. Alternatively, capacity calibration can be an iterative process.
       To calculate a CAF, the segment capacity is divided by the HCM base capacity to arrive at the capacity adjustment factor. For example, at FFS=60 mi/h the HCM base capacity is 2,300. If a bottleneck segment has a capacity of 2,100, the resulting CAF=2,100/2,300=0.91. For a bottleneck with a capacity of 2,000, the calculation is CAF=2000/2300=0.87.
       Similar to SAFs, CAFs for bottlenecks generally apply for the entire 24-hour period. Special CAFs for shorter duration events (e.g. nighttime work zones, incidents, or weather events) are specified separately after the base calibration is completed.
       PRO TIP: FREEVAL-PA includes a capacity display to double-check the computations math. 
    4. At this point, the user should evaluate the facility end-to-end travel times and speed contours and compare to the field data. It may be useful to save these initial calibration results, before making further changes.
    5. Next, the user should calibrate unusual/tight geometries to reflect further adjustments that may be needed. These additional CAFs should also be entered in the "Seed Capacity Adjustment Factor" input. In some cases, CAFs can be adjusted up relative to step 3, if the predicted queuing is more severe than the field data shows. But in most cases, this step will further reduce capacities since field data shows more severe queuing than FREEVAL prediction. Step 5 may involve multiple iterations to get close to the field-observed data. The iteration may also include demand adjustments (see Step 6), but generally should not change the SAFs previously calibrated for off-peak conditions.
       PRO TIP: In making these adjustments, it is important that the user has a good understanding of freeway operations and causes of congestion. For example, queuing generally occurs upstream of a bottleneck, so the FREEVAL-PA capacity adjustments are applied to the segment immediately downstream of the queue.  
    6. As a final calibration step, the user can adjust volume inputs through "demand adjustment factors". This is most commonly used when FREEVAL-PA correctly identifies a bottleneck location but may not correctly represent the duration of the congestion (time periods the bottleneck is active). In this case, the underlying volume profile should be checked to make sure that the arrival patterns at the bottleneck match field data. When sensor data used to set up FREEVAL is obtained from a congested freeway, it is possible that the bottleneck volumes and counts were metered by upstream congestion. In this case, the user can adjust volumes up or down using demand adjustment factors to increase or decrease congestion, respectively. Demand adjustments should be a last resort and may be an indication that there is a problem with the original volumes entered into the tool.  
  • Where do I find reliable calibration data?

    Calibration data covers three separate data sources:

    1. Volume data
    2. Speed and Travel Time Data
    3. Capacity data.

    Volume data can be obtained from PennDOT’s TIRe website (https://gis.penndot.gov/TIRe) for sensors across the state. Input volumes for a FREEVAL-PA analysis should generally be obtained upstream of any congestion to assure that true demands are measured. Volumes can also be obtained for on-ramps and off-ramps if available, or ramp volumes can be calculated by subtracting upstream and downstream mainline sensors. Volume data can also be helpful at interim locations on a facility to validate volumes processed by a facility. Just as for other traffic analysis tools, the volume development process typically occurs in advance of the operational analysis in FREEVAL-PA.

    Speed and Travel Time data are obtained from PennDOT’s portal to the RITIS probe database. Consultants can request access for PennDOT projects to this data source. The probe data can be filtered for a specific facility and time period (days, weeks, months) to match the desired FREEVAL calibration. The RITIS portal also provides online displays of end-to-end travel times, as well as speed contours that can be used for calibration.

    Capacity data can also be obtained from PennDOT’s TIRe website for specific bottleneck locations of interest. A detailed procedure for estimating freeway bottleneck capacity is contained in Highway Capacity Manual (HCM) Chapter 26 - Freeway and Highway Segments: Supplemental, which is available for free on the HCM Volume 4 website (https://hcmvolume4.org/).

  • What inputs are needed for a detailed analysis?

    The minimum required data to conduct a detailed analysis in FREEVAL-PA are:

    1. Facility Geometry (number and type of segment);
    2. Geometric Details (merge, diverge, and weaving geometry details);
    3. Grades and truck percentages; and
    4. Volumes for all entry and exit points to the facility

    Using the FREEVAL-PA segmentation database, items 1 through 3 are available for all limited access facilities in PA, not including the turnpike. For item 4, FREEVAL-PA can be set up initially with an Average Annual Daily Traffic (AADT) value for the mainline input and all on-ramps and off-ramps, which can then be distributed with one of three default volume profiles to arrive at the needed 96-time periods in a 24-hour analysis (see below for details).  As such, very little information is needed to initially configure a facility. However, it is emphasized that while this initial set-up is quick, additional work is needed to calibrate a facility using the procedures and data sources described above.

  • Has the base model already been calibrated when obtained through the segmentation database?

    No! The segmentation database contains the geometric data for all limited access facilities in PA (not including the Turnpike), but not facility-specific calibration data. The database contains segment types (basic, merge, diverge, weaving), segment lengths, segment geometry (number of lanes, acceleration and deceleration lane lengths, weaving geometry), roadway grades, and truck percentages. The database does not contain traffic volume data (as these vary based on the analysis performed), nor the specific calibration details. As such, every detailed analysis in FREEVAL-PA should contain a calibration step as described in the user guide and the FAQs.

  • Where do I find the best base CAFs and how do I apply them to the model?

    The CAF, or Capacity Adjustment Factor, represents the ratio between the specific bottleneck capacity and the “ideal” segment capacity in the HCM. The idea capacity for a basic segment with free-flow speed (FFS) of 70 mi/h or higher is equal to 2,400 pc/h/ln (passenger cars per hour per lane). For lower free-flow speeds, the ideal capacity is reduced by 50 pc/h/ln for each 5 mi/h drop in FFS (65 mi/h à 2,350 pc/h/ln; 60 mi/h à 2,300 pc/h/ln, etc.). The bottleneck capacity can be estimated using the PennDOT defaults included in FREEVAL-PA, from field-measured capacity estimates following the HCM procedure (see FAQ on calibration data), or through an iterative calibration process (see FAQ on calibration steps). The CAF is then calculated by dividing actual capacity by ideal capacity to obtain a CAF that is typically less than 1.0. For example, a bottleneck segment with capacity of 2,000 pc/h/ln and a free-flow speed of 70 mi/h, the CAF is calculated as CAF=2,000/2,400=0.83.

    FREEVAL-PA also allows for specification of CAFs to reflect capacity impacts of non-recurring sources of congestion, including work zones, incidents, and weather. These adjustments are applied through the FREEVAL-PA scenario manager (see FAQ on Scenario vs. Alternative Analysis). These CAFs are multiplicative to the calibration factor. For example, in the bottleneck example above with capacity of 2,000 pc/h/ln and resulting in a calibration CAFcalib of 0.833, a work zone would further reduce the capacity. If the work zone capacity is 1,600 pc/h/ln, the resulting work zone adjustment CAFWZ=1,600/2,000=0.800. Alternatively, the same work zone could have been modeled through one overall CAFTOTAL=1,600/2,400=0.67, which yields the same result as CAFcalib*CAFWZ=0.833*0.800=0.67. However, while the computational results are the same, it is recommended to keep the two CAFs distinct whenever possible. This will allow more careful tracking of the different adjustments, and will further allow the scenario comparison (in this case calibrated base vs. work zone) in the scenario manager within FREEVAL-PA.

  • What are the default volume profiles?

    To facilitate the volume input process, three default volume profiles are available in the FREEVAL-PA tool (AM peak hour, PM peak hour, and Rural/Weekend). The volume profiles are used to distribute the Average Annual Daily Traffic (AADT) inputs across the 96 fifteen-minute analysis periods. The three default profiles represent the following conditions:

    • The AM peak hour profile is used for a route with a morning commute pattern.
    • The PM peak hour profile is used for a route with an afternoon commute pattern.
    • The Rural/Weekend profile is used for a route without a clear AM or PM peaking pattern.

    Each profile also has different levels such as: average, 15th and 85th percentile, and maximum to allow further customization. While these default volume profiles allow for an initial assessment, it is strongly recommended to replace these with facility-specific volume profiles that can be developed from sensor data obtained from PennDOT’s TIRe website as described above.  In the Detailed Analysis part of the program the user may specify custom volume profiles to reflect facility-specific patterns. This is particularly important for the mainline input, as well as for major merge and diverge points along the facility.

  • When should FREEVAL-PA inputs be modified?

    Once all the facility inputs have been entered and a preliminary evaluation of the outputs has been performed, it is expected that analysts will need to use the methodology to further calibrate the facility, to test various scenarios, or to perform sensitivity analyses. FREEVAL-PA is designed to allow the user to revise input data and make changes to geometry, demand, and other input variables to test the effect of such changes on the operations of the facility. Motivations to revise inputs include:  

    • Calibrating a facility to match observed flows.  
    • Testing sensitivity of increased volumes due to traffic growth or traffic diversion to other routes. 
    • Testing geometric changes such as added lanes, different ramp configurations, or alternate weaving patterns in select segments. 
    • Testing the operational effects of work zones and/or incidents through changes in segment capacity and/or free-flow speeds.  

    FREEVAL-PA provides four types of adjustment factors that are intended to assist the user in performing facility calibration and basic sensitivity analyses:

    • Origin/Destination Demand Adjustment Factors, 
    • Capacity Adjustment Factors, 
    • Free Flow Speed (FFS) Adjustment Factors, and  
    • Driver Population Adjustment Factors.