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Highway Performance Monitoring System (HPMS)

Field Review Guidelines

Revised June 2001

Introduction

The HPMS data are seeing wider use within FHWA, the transportation community, and a general public that is more and more concerned with where its tax dollars are going. The HPMS data are key markers of FHWA program performance: safety measures in terms of fatalities and injury crashes are benchmarked to VMT; pavement smoothness to IRI; and changes in congestion levels to estimated system delay. Federal-aid highway fund apportionments are linked to HPMS data: miles, lane-miles and VMT are all used in apportioning IM, NHS, and STP fund categories to the States. NHTSA uses public road miles to apportion safety funds to the States. Congress bases determinations of highway program funding levels in significant part on FHWA's biennial Conditions and Performance Reports that document future investment needs. These measures, functions, and reports are ultimately dependent upon the provision of timely, complete, and accurate HPMS data.

The States exercise ownership of the HPMS data; it is their data, not FHWA's. While as an agency we collect, screen, accumulate, disseminate, and use these data, they are still the data that have been prepared by the States and cooperating units of local government. The quality and integrity of these data rest with the processes that the State has put in place to create the basic data inputs. The questions, concerns, and criticisms that come from the varied data users reflect directly on the States' ability to accurately portray the condition and performance of their highway systems. FHWA can provide tools, training, and technical assistance to States, but ultimately it is a State responsibility to provide quality data.

The field offices of FHWA provide an invaluable stewardship role, a gatekeeper function. The field offices have a stake in assuring that the HPMS data provided by the States meet FHWA needs for accurate performance measures, apportionment factors, and congressional budget justification. Measuring how well the federal-aid program is working in each State, assuring that each State gets its fair share of funds, and assuring that the investment needs of each State are accurately portrayed to the Nation's leadership is an important responsibility that rests primarily at the division office level. Of necessity, this means that the field offices must partner with their State counterparts to assure that the HPMS data are the product of a rigorously defined, well managed, and adequately funded data acquisition and reporting process and that what is ultimately provided to FHWA by the State is complete, timely, and accurate.

Headquarters provides an overall coordinative role in the HPMS data process. Reporting standards are set out in the HPMS Field Manual; reporting software has been developed and provided to the States; technical assistance, advice and training are regularly provided to field offices and the States; data are reviewed against prior year reports, normative trends, and other States to identify possible shortcomings; summaries, calculations, and estimates of performance measures and apportionment factors are prepared and provided to agency managers. However, no amount of headquarters review can make up for an informed review by the State data owners and the FHWA field office stakeholders of both the data and the processes by which the data are produced.

Purpose

The purpose of these guidelines is to provide recommendations to the Divisions on how they, with the assistance of the resource centers and headquarters, can best fulfill FHWA's HPMS data quality objectives. The guidelines contain specific information on annual reporting requirements and on the review of significant data trends for length, lane miles and travel data used for apportionment purposes; they also include advisory information on conducting program and process reviews of several of the more prominent data collection activities covered by the HPMS.

The guidelines provide for maximum flexibility at the division level; it is up to each division to decide which data areas they need to focus on to improve the quality of the HPMS program for the State. Each division is responsible for developing, prioritizing, conducting, and reporting appropriate HPMS data, program, and process review activities. Although the divisions have primary responsibility for deciding the priority of process reviews to be conducted, headquarters will work with the divisions to ensure that all identified high priority data issues are thoroughly resolved as part of our ongoing data quality improvement activities.

The advisory guidelines are to be used by the field staff as an aid to developing process reviews appropriate to the particular conditions or problems that may exist in any of these technical areas for the specific State to be reviewed. While not all encompassing, they do cover the data reporting areas considered to be of the highest priority for assuring that quality HPMS data are available to meet FHWA's responsibilities for apportionment, performance measurement, and condition and performance reporting to Congress.

General

The annual review of HPMS data by each division includes four components: (1) program reviews of high priority subject areas, (2) field inventory reviews, (3) annual required reviews, and (4) annual reporting. These are discussed further in the following sections.

High Priority Subject Areas To facilitate field review activities, headquarters, as part of its annual review of HPMS data submitted by the States, will identify what we see as potential problem areas and data issues to the divisions. Data item problems are usually identified as being of high priority because they have a potential to significantly impact upon the apportionment of Federal-aid highway funds, or the biennial Condition and Performance Report to Congress, or FHWA's ability to provide required performance information; high priority data items and issues will be highlighted in the review comments returned to the divisions. These include, but are not limited to, the high priority subject areas identified in the Appendix:

High priority areas identified in the Appendix should be regularly surveyed on no more than a 3-year interval to determine if in-depth program or process examinations are needed; issues which are specifically identified in the headquarters review comments should be considered for immediate action.

The scheduling of program or process reviews for high priority areas should be determined by the division and State based upon the most vulnerable aspects of the State's HPMS program; data items having the most significant effect upon the quality of the HPMS database should receive higher priority. The divisions should review those problem areas identified by headquarters and place an emphasis on examining, in-depth, issues related to the associated data items and the State's underlying data collection and reporting processes during the following program year. Assistance in conducting process reviews can be provided by resource centers, headquarters, and other States in a peer review role. The teaming of FHWA and State resources to resolve high priority data issues is strongly encouraged as a way to foster knowledge sharing on improving HPMS data.

Field Inventory Reviews

Each division should establish a schedule to review HPMS inventory data on a basis that is consistent with good data quality management practice. Although the divisions are responsible for determining how often to conduct overall field inventory reviews of the State's HPMS data, a 3-year cycle is recommended. The objective of these reviews should be to ensure that data being entered by the States into HPMS match field conditions. This does not necessarily need to be a formal activity. Traveling to an MPO meeting by car? Mark a map with HPMS sample sections on the route you are taking and stop along the way to compare field conditions with reported data. The ITDB can be used to look at mapped sample locations and to pull up related HPMS data records via the Internet before you leave the office.

The data items reported into HPMS which should be reviewed periodically on a sample basis by the divisions include at least the following: type of facility, number of through lanes, number of peak lanes, type of signalization and percent green time, type and number of at-grade intersections, median type, shoulder type, access control, surface and pavement type, speed limit, turning lanes (urban only), peak parking (urban only), and high occupancy vehicle operations and surveillance data. The divisions should also verify by observation if the median width, shoulder width, lane width, and curve and grade data reported for the HPMS sections reviewed are reasonable.

Annual Required Reviews

Data Trends Examination

The divisions must annually certify that the State's public road mileage data, highway vehicle-miles traveled (VMT), and lane miles data are valid and suitable for use in the apportionment of Federal-aid highway funds. Each year, the divisions should examine the data trends for reported AADT, public road mileage, travel both on and off the State system, and number of lane miles for reasonableness before making the certification. Prior year trend information can be found on the FHWA Office of Highway Policy Intranet staff site at: http://intra.fhwa.dot.gov/ohpi/index.htm

Mileage Certification Review

The total extent of public road miles certified as of December 31 of the data year (23 CFR 460) must be the same as those reported in that calendar year's HPMS data. States have the primary responsibility for certifying State and local government estimates of owned roads in their respective States. In addition, the annually certified public road miles and the HPMS data base reported miles should conform to lengths reported by Federal agencies having public roads in each respective State. Entities owning public road miles that must be included in the certified total include State transportation agencies, other State agencies, county and town governments, Indian Nations, toll commissions, airports, Federal agencies and public/private partnership roads.

Annual Reporting

Divisions are responsible for demonstrating in an annual review memo to headquarters that their respective States have a satisfactory HPMS data program in place. This annual review memo is due by November 1 of each calendar year.

The review memo should cover the results of the data trends and mileage certification reviews, as well as the results of any process reviews conducted during the year. The review memo should also document any FHWA actions taken or recommendations made as a result of the review and steps the State is taking to make improvements in deficient areas or processes. High priority data areas needing improvement should be specifically noted in the review memo along with the actions taken to remedy previously identified problems. Follow up reporting by the division of issues, recommendations and results on a year-to-year basis is essential to staying on the path to quality improvement over time. And, in an era of rapidly changing staff responsibilities, it is important to maintain an adequate record of progress. Significant changes by the State in the oversight and management of programs and processes providing HPMS data should be a consideration in determining if further reviews are needed.

Additional Considerations

Whenever a review is performed, the division should address adequacy of funding for the HPMS program for both the States and MPOs. The adequacy of personnel and equipment, and training needed by State and local entities to conduct the HPMS program in a quality manner, also should be examined by the division.

Issues identified by the divisions should have a schedule for addressing problems identified in any data or process reviews. Resolution of high priority data issues should be a factor in determining priorities for funding of activities in State Planning and Research (SPR) and Unified Planning Work Programs (UPWP).

When a State contracts for data provision with a private vendor, MPO or local government, or toll facility, the State should have a reasonable means of validation to ensure that properly collected, current data are being reported. The division should review the State's process for assuring accuracy of these data.

The HPMS submittal software and the ITDB are excellent tools to use in examining the quality of data submitted by the States. The divisions are encouraged to learn how to use these tools for reviewing the quality of their States HPMS data and for conducting in-depth program and process reviews of critical HPMS data areas. The divisions should make full use of the HPMS Field Manual as a resource when developing and coordinating data and process reviews.

Quality HPMS Data An Important FHWA Agency Objective

Information and Analysis is a key cornerstone of the Malcolm Baldridge criteria which FHWA uses as a measure of our agency's performance to determine if we are meeting the needs of our customers, States, Congress, and the public in providing quality data which accurately represent the travel characteristics and extent of our Nation's road system. How we effectively manage the quality of HPMS data has a direct impact on FHWA's ability to assess our progress in meeting agency performance objectives for the Strategic and Annual Performance plans. The proactive assistance of the divisions and resource centers in working with the States and MPOs on improving the quality of HPMS data should be a critical component of planned division and resource center work activities. Improving HPMS data and processes should be included in the division's performance plan objectives and self assessments; improvements should be accomplished working with the State DOTs and MPOs. We encourage the teaming of division, resource center, headquarters and State staff to resolve issues which have a significant effect upon the quality of HPMS data, and to provide an opportunity for knowledge sharing as part of meeting our agency goals of developing high quality roadway information for our customers.

APPENDIX

Process Review Guidelines for High Priority Subject Areas

The following review areas have been identified as having a potential for significant impact on the HPMS and data quality. Under each subject area are some important issues that the Division should consider when deciding to conduct a detailed review. The identified issues are not all encompassing; they are presented to aid the Divisions as they and the State develop appropriate guidelines before conducting process reviews. The related chapters and appendices in the HPMS Field Manual and the Traffic Monitoring Guide (TMG) should also be consulted when preparing review guidelines.

Traffic Data Reporting

As part of an in-depth review of traffic data reporting, the Division should investigate the following issues:

  1. How is the State meeting the minimum 3-year HPMS reporting requirement for traffic data?

    As discussed in the HPMS Field Manual, Appendix F, traffic volume counts are to be taken for all HPMS standard sample sections and for all principal arterial (PAS) and NHS universe sections once every 3 years, preferably with 1/3 of each functional system counted each year. Monitoring of traffic on all PAS/NHS roadway sections is requested to enhance the level of precision of traffic volume data on the Interstate and NHS routes. The program should cover all urban and rural roads, not just State owned roads, and should include counts made on the State's behalf by MPO's, cities, and counties. These counts serve as the basis for developing both AADT estimates for each HPMS universe and standard sample section and, through sample expansion, system wide daily vehicle-miles of travel (DVMT). AADT reported for sections in non-count years should be current estimates based on appropriate growth factors.

  2. How does the State assign AADT data values to other roadway sections?

    Reasonable AADT estimates on all State and off-State system roadway sections, in addition to the counts taken on sample sections, the PAS, and the NHS, are needed to assign roadway sections to proper volume groups in the sampling universe. Periodic coverage counts, recommended on a 6-year cycle in the HPMS Field Manual, can be used to derive a useable estimate of mileage by volume group; some States use traffic flow mapping to accomplish this task. Correct assignment of roadway sections to volume groups is necessary to aid in sample selection and to calculate valid expansion factors; this affects the validity of all travel estimates and other expanded HPMS sample data items. Monitoring traffic on a coverage basis is discussed in Chapter 2 of the AASHTO Guidelines for Traffic Data Programs.

  3. How are the States and MPOs applying seasonal and axle correction factors to counts taken in the development of AADT values?

    A brief summary of these are explained below for reference. Additional information on the traffic factoring process can be found in Section 3 of the TMG.

    Seasonal Factor:

    Seasonal factors are used to adjust short volume counts (48-hour counts) and develop AADT estimates. This involves first calculating factors for each automatic traffic recorder (ATR) station using the ratio of AADT and monthly average daily traffic (MADT) and then averaging the factors for the ATRs falling into each of the seasonal groups (Interstate Rural, Other Rural, Interstate Urban, Other Urban and Recreational). Approximately five to eight ATR locations are recommended per seasonal group to assure the desired precision levels recommended in the TMG.

    Day-of-the-Week Factor:

    Adjustments for day of the week are to be used where it is shown to be necessary to provide data for an average day of travel. In general, the decision whether or not to use this adjustment factor should be based on the judgement of the analyst as guided by State conditions and supported by the interpretations derived from the data. To this end, adequate documentation should be maintained to support the decisions made and to allow future reexamination. Day-of-the-week factors can be computed on an individual basis for each of the seven days of the week or for combined weekday and weekend factors. Where day-of-the-week factors are used, they should be used for each of the seven days of the week.

    Axle Correction Factors:

    The application of axle correction factors is dependent on the type of equipment in use. It is important to use axle correction factors with pneumatic tube detectors as they do not account for vehicle type. The number of axles counted needs to be adjusted to reflect the vehicle mix of traffic on the roadway. Axle corrections based on vehicle classification should be applied to all counts obtained from axle sensor devices.

    The axle adjustment factor at a point is simply the ratio of vehicles to axles as determined from a classification count. The axle adjustment factor for a functional system is the average of the individual factors of all the classification locations within the specific functional system.

    Application of axle adjustment factors will depend on the particular situation. Correction factors by functional system are sufficient for the purpose of developing volume counts on a system wide basis. Documentation of axle correction factors used is required to demonstrate that:

    1. The data is representative of each specific functional system.

    2. Each season of the year is represented in the development of the axle corrections.

    3. The monitoring session durations are sufficient to account for the changes in vehicle mix from day to day (at least 48-hour counts).

    4. The total volume of vehicles observed is at least equal to that for an average day.

    5. Classification counts are well distributed among rural and urban locations.

    6. Although classification counts may have been spread over a 3-year period, the current year is included as one of the three.

    7. There are sufficient categories to represent vehicles with two to seven axles.

  4. The Division should review how the State schedules and conducts traffic data collection activities for standard sample, PAS/NHS universe, and periodic system coverage counts.

    Issues to consider include whether all mileage on or off the State system is counted, whether each HPMS standard sample and each universe PAS/NHS universe section is covered on a 3-year cycle, if there is a minimum 48-hour count performed at each site, and whether or not traffic data collection at selected sites is randomly scheduled in terms of time and location to better ensure statistical validity. Types of traffic monitoring equipment used, equipment accuracy validation, monitoring of contracted data collection and related issues also should be reviewed.

  5. What is the extent of coverage of ATRs for State and off-State system roads? What uses does the State make of its ATR data?

    Among other applications, ATR data can be used for the development of seasonal factors to expand short-term counts to AADT. Data from State's ATRs are reported to FHWA Headquarters for reporting in the monthly FHWA publication Traffic Volume Trends.

    In developing a network of continuous ATRs, the State must consider a variety of factors including highway functional classification and rural/urban character in establishing its sampling plan. The desired precision and confidence of the data must also be established. The recommended levels (from the TMG) are 10 percent precision and 95 percent confidence for the individual seasonal groups except recreational which has no precision requirement. The TMG recommends States establish five groups (Interstate Rural, Other Rural, Interstate Urban, Other Urban and Recreational) with five to eight ATRs assigned to each group, resulting in a minimum recommended statewide total of about 40 ATR stations. Larger than normal changes in AADT at ATR sites, based on past trends, should trigger an examination of reasons for the changes and the reasonableness of the reported values.

  6. Determine if reported AADT values for HPMS sections are reasonable based upon past trends.

    The HPMS submittal software identifies changes in reported AADT from year to year on HPMS sections. Larger than normal changes in AADT based on past trends should trigger an examination of reasons for the changes and the reasonableness of the reported values. The software also compares AADT and the reported number of through lanes based upon a maximum traffic capacity of 2,200 vehicles per lane per hour for interstate (2,000 for other systems) and identifies sections with possible problems. For these cases, the reported number of through lanes for the section and the AADT values reported should be examined for possible error; unreasonably high calculated highway capacity values can result from an incorrect reporting of through lanes or AADT on sample sections.

  7. How are traffic growth rate factors used by the State and MPOs determined and applied?

    Growth factors are generally determined from ATR data trends and applied to uncounted roadway sections to develop a current year AADT estimate. State-wide rural and urban growth rate factors applied to all routes or to entire functional systems can significantly bias the true growth rates of various transportation corridors of the State. The application of route specific growth factors, or growth factors for individual urban or urbanized areas, or factors for State sub-areas having similar growth characteristics (rapid versus slow growth, for instance), provide a better basis for estimating traffic growth.

  8. Are traffic growth rates realistic when compared to actual growth in counted traffic?

  9. Does the State have a systematic process in place to ensure that contractors, MPOs, and other providers of traffic data are following recommended HPMS procedures and State practices for collecting and reporting traffic data? What are the details of the State's data review procedures?

  10. How often are the State's and MPO's documentation of their traffic data development procedures updated? How current are existing procedures? FHWA should work with the State and the MPOs to ensure that their traffic estimation procedures are well documented and current. FHWA should facilitate knowledge sharing of traffic data development practices and procedures between the States and their respective MPOs.

Reference Documents:

Total Public Road Mileage Reporting

When conducting an in-depth review of public road mileage reporting, issues the Divisions should examine include:

  1. What are the procedures used for identifying and reporting centerline road miles for each roadway owner reporting public length?

  2. Does the State have a process in place to verify the public road lengths and locations of these roadways reported to them by other agencies? How often is this data verified by the State DOT?

  3. Is a mapping identification made to assure that the correct roads are identified and that duplicate reporting has been avoided across jurisdictional boundaries?

  4. For each road owner, how often are mileage statistics updated?

  5. How do reporting agencies determine the lengths of their system roadways? Is the average length of both road directions used or is a single direction measured and reported?

  6. How does the State verify that roads not open-to-the-public are not being reported in HPMS?

  7. What funding programs does the State have with local government owners to encourage the reporting of accurate lengths of public roads?

  8. What activities should be improved by contributing agencies for the reporting of public road length?

Reference Documents:

23 CFR Section 460 "Public Road Mileage For Apportionment of Highway Safety Funds" HPMS Field Manual, Chapters I, II, and IV Item 25 "Governmental Ownership" FHWA Memorandum from Gary Maring, Office of Highway Information Management, to Division Administrators "Reporting Federal and Other Government Agency Owned Public Road Mileage", January 21, 1999

Travel Data (VMT)

VMT data is an important factor in calculating Federal-aid highway apportionments. Travel is calculated from traffic data and corresponding section lengths entered into the HPMS data base. Travel by functional system and specific Interstate routes should be reviewed for significant increases or decreases. Larger than normal changes, based on past trends, should trigger an examination of reasons for the changes and the reasonableness of the reported values. Reviews should address both reported length and traffic data for functional systems and routes examined.

Issues the Divisions should examine include:

  1. Is total VMT by functional system reasonable for the reported year and are comparisons to prior years reasonable?

  2. Are total rural and total urban VMT data reasonable and are trends consistent?

  3. Determine if changes in VMT by functional system reasonably reflect recent annual trends within geographic sub-areas of the State.

  4. Is functional system VMT by urbanized area reasonable based upon past trends and are comparisons among urbanized areas reasonable?

  5. Compare reported VMT and MPO VMT estimates for consistency at the functional system and/or urbanized area levels.

  6. Are HPMS generated VMT used for air quality conformity purposes in non-attainment areas? Are there unresolved issues or problems associated with their use?

  7. Can significant changes in VMT trends be justified? Review the adequacy of the documentation supporting these travel changes.

  8. Determine how changes in route miles are reported and documented by the State or MPOs; do the route mile changes appear reasonable based on past trends? How does the State monitor local government mileage data changes?

Reference Document:

HPMS Field Manual, Appendices F and G

Off-State System HPMS Data

In some States, data reporting is often not complete for non-State system roadways. The inadequate reporting of off-State system data can adversely affect travel and pavement condition measures. Off-State system data gaps can significantly bias many HPMS data uses including condition and performance reporting, development of apportionment factors, and performance reporting against strategic objectives. State and other participants in the HPMS reassessment process reaffirmed the desirability of retaining information on all roadways in HPMS; this requires reporting of both on- and off-State system road data. In some cases, States simply do not report current data for non-State owned HPMS sample sections; in other cases, States exclude non-State owned roads from the sample entirely.

Issues the Division should examine include:

  1. Ideally, HPMS samples should have been randomly selected from State and off-State system roads. While a random sample will not guarantee proportionality, it is useful to determine if off-State system miles are somewhat proportionally represented in the HPMS sample (percentage of miles). If there is significant over representation of State system roads in the sample, has the State biased the sample through a non-random selection process by sampling only State-owned roads? Does the State continue to bias the sample by continuing to pick new HPMS sample sections from State system roads only? Does the "pool" for sample selection include all State and non-State system miles?

  2. How does the State obtain its off-State system HPMS data? How current is the data and what is the update cycle?

  3. How is the AADT used to determine volume group for sample selection obtained for off-State system roads?

  4. How does the State verify the accuracy of off-State system data entered into the HPMS data base when obtained from other sources?

  5. What data sharing and cooperation exist between the State, MPOs, or other local entities providing HPMS data?

  6. Does the State know how its MPOs/locals develop traffic or other data submitted to HPMS?

  7. Does the State have a systematic check in place to ensure that the MPOs/locals are following recommended HPMS procedures for traffic and other data? Review the State's procedures in detail.

Reference Document:

HPMS Field Manual, Chapter VII

Consistent Future AADT Estimates

Forecasted AADT from standard sample sections is used to estimate future system deficiencies and improvement needs for Congressional reporting. Forecasted traffic should be for a period covering 18 to 25 years from the HPMS data year. In urbanized areas, resulting estimates of travel should be consistent with those of MPO's at the functional system and total urbanized area levels. Reported HPMS future AADT values should be checked with the MPOs prior to submission and differences resolved, if possible. In order to retain program credibility, it is important that consistent traffic and travel forecasts are maintained for planning, air quality conformity, and other uses.

Issues the Division should examine include:

  1. How does the State obtain its future AADT estimates?

  2. What procedures are used by the State to develop future AADT estimates?

  3. Are estimates of future AADT provided by MPOs for urbanized areas and how are they estimated? If done by the State, are estimates benchmarked to MPO future travel estimates by functional system and urbanized area total? How often are future estimates provided by the MPOs updated?

  4. How is future AADT data estimated for sections in rural areas off the State system? Small urban areas?

  5. If provided by others, how does the State review estimated future AADT data for reasonableness and accuracy?

Reference Document:

HPMS Field Manual, Chapter IV, Item 97 (Future AADT)

HPMS Sample Adequacy and Sample Bias

Initially, the original HPMS sample should have been randomly selected from all roads in all geographic areas of the State. Over time, changes to the sample, both additions and deletions, should also have been accomplished through a random selection process. The use of other than random sampling can introduce bias into the sample, and sample bias can adversely affect expanded sample travel estimates and other HPMS data applications relying on an expanded sample. With greater reliance on using the expanded sample for calculating travel and performance data, good sample management is an important consideration.

Some of the issues the Division should examine include:

  1. Is there evidence of possible sample selection bias in the HPMS sample?

  2. How often does the State run the HPMS sample adequacy software to ensure that the number of samples per volume group meets HPMS sampling requirements? Are there any problems or issues in meeting sample adequacy requirements? Has the sample been updated when required? Is the sample reviewed and updated on a periodic (3-year maximum) basis?

  3. When the sample is modified, how are additions or deletions made? Does the State use a random process for sample additions and deletions? Are all roadway sections considered when selecting new samples, not just State-owned roads or adjacent roadway sections because they are convenient?

  4. For non-attainment areas, is the donut area sample panel also evaluated and updated on a periodic (3-year maximum) basis?

  5. If there is significant evidence of sample bias or a neglect of sample updating, the Division should discuss the possible need for a complete sample reselection with the State.

Reference Document:

HPMS Field Manual, Chapter VII and Appendix K

Highway Capacity Related Data

Highway capacity information is used in the Condition and Performance Report to Congress, for FHWA performance and strategic planning, and for other purposes. These uses rely upon capacity-related data from the HPMS. Some of the more significant data items which contribute to the quality of highway capacity estimates include percent trucks; turning lanes; at-grade intersections; percent green time; shoulder type and width; number of peak lanes; lane width, median width, median type, and "K" (design hour volume) and "D" (directional) factors.

Some issues the Division should examine include:

  1. How often are K and D factors updated by the States and MPOs? What is the method of estimating these data and assigning them to sample sections? These factors are generally determined from ATR data and applied to sampled roadway sections. State-wide rural and urban K and D factors applied to all routes or to entire functional systems are less desirable than the use of route specific factors for similar facilities, factors by functional system for individual urban or urbanized areas, and/or factors by route or functional system for State sub-areas having similar growth characteristics (rapid versus slow growth, for instance).

  2. Does the State have realistic numbers of at-grade intersections assigned to HPMS sections? If not, is there an effort to review these data?

  3. How often does the State update its percent truck data? What is the source of the data and how is it assigned to HPMS sample sections? These percents are generally determined from classification station count data and applied to sampled roadway sections. State-wide rural and urban truck percents applied to all routes or to entire functional systems are less desirable than the use of route specific percents for similar facilities (known through truck routes, for instance), percents by functional system for individual urban or urbanized areas, and/or percents by functional system for State sub-areas having similar economic activities and characteristics (recreation areas versus mineral extraction and mining, for instance). Is there sharing of such data with the MPOs?

  4. How does the State estimate the prevailing green times for actuated and other traffic signals?

  5. For other important capacity-related data items such as peak number of lanes, lane width, median width, shoulder width, peak parking, functional classification, section length, median type, and type of access control, does the State have a program in place to update changes to these data items and to verify that they are being correctly reported in the HPMS?

Reference Documents:

HPMS Field Manual, Appendix N Highway Capacity Manual, 1997 Edition

Pavement Data:

In response to a 1999 GAO report to Congress, FHWA has made a high level commitment to work with the States to improve the quality and consistency of pavement roughness data; the Divisions should determine the most appropriate level of review of pavement data with this commitment in mind. The assistance of Division pavement specialists should be utilized in designing and conducting pavement reviews.

The HPMS pavement roughness data monitoring process review should evaluate the State's collection of pavement condition data including collection equipment and procedures for gathering this data. The Division and State DOT should determine the frequency of performing this type of process review based upon an initial assessment of data quality and procedures used, as well as supporting information on the condition of the State's pavement management system. Headquarters' comments on annual HPMS data submittals should be considered. State procedures should be in accordance with Appendix E of the HPMS Field Manual.

In conducting process reviews on pavement roughness data, Divisions should examine the following issues:

  1. Is pavement roughness data for required functional systems collected on a 2-year cycle? If not, what update cycle is used and what are the State's plans for meeting the 2-year HPMS cycle requirement?

  2. Is old pavement roughness data retained and reported until it is replaced by new data? Is "0" reported for sections where data are not available? Does the State report measured IRI only or is IRI converted from other data such as PSR?

  3. Does the State adhere to AASHTO Provisional Standard PP37-99? If not, what are its plans for doing so?

  4. Does the State select one direction for measuring pavement roughness for HPMS sample sections for use throughout the State (for example east to west and south to north)? Does the State use the same direction for measuring an HPMS sample section each time pavement roughness data are collected?

  5. For multi-lane facilities, which lane(s) does the State use to collect roughness data? For HPMS, we recommend that the outside right lane be used in measuring pavement roughness. The same lane should be used each time pavement roughness data is collected.

  6. Are bridges and railroad crossings excluded from pavement management roughness data reported in HPMS as recommended by FHWA?

  7. Does the State collect roughness data for off-State system roadways? How is this data collected? If collected by a contractor or other non-State entity, how does the State confirm the accuracy of reported IRI data?

  8. Is the data reported in HPMS consistent with roughness data in the State's pavement management system?

Reference Documents:

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