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HPMS Reassessment 2010+

Final Report

Prepared by:

Office of Highway Policy Information
Federal Highway Administration

Appendix D: Issue Papers

Pavement-Related Data Issues


1. Frequency of submitted/reported IRI data.

  • Require States to report IRI and IRI Year annually on a universe basis on the NHS. (The collection of IRI data off the NHS could remain on a 2-year cycle, since its primary use is to support a biennial report and is published in tables).

2. Consistency of submitted/reported IRI data.

  • Better “enforce” the current collection procedures and requirements of IRI in the HPMS based on AASHTO PP37-04.
  • Report various metadata and date of collection, including IRI Year, on IRI from the States (as currently defined in HM-66 of Highway Statistics or modify).
  • Continue reporting average of both right and left wheel path quarter-car IRI in HPMS (MRI).
  • Report IRI data on structures and railroad crossings where IRI is required.

3. Collect additional pavement data items and drop less useful ones.

  • Implement standards (AASHTO) and collection procedures in HPMS for the collection of all of the defined additional pavement data items as required sample data items. Define and require reporting of metadata for applicable data items.
  • Drop reporting of SN. Need for this data item is obsolete and redundant based on acquisition of new data items.
  • Collect additional pavement data items through a mix of required fields, optional fields, phased-in reporting, and Statewide default tables.
    • Rutting/Faulting: Add as required sample data items (data to be collected via profilometer at same time as IRI).
    • IRI Year: Add for all sections where IRI is required (including structures).
    • Cracking: Add % cracking (regardless of severity) as an optional sample data item, to allow States to provide information if their data is consistent with a standard FHWA definition.
    • Add a separate HPMS table for data items that only change when an improvement occurs. Include the historic data items as listed above and shown in the table on page 9.
    • Date of Last Overlay and Date of Last Reconstruction: Add as required sample data items.
    • Thickness of Latest Overlay: Optional sample data field until next post-2010 overlay.
    • Existing Asphalt Bound Thickness, Existing Concrete Thickness, Base Type, Base Thickness: Optional sample data fields until next post-2010 reconstruction. For off State-system, allow States to code based on State design standards (i.e., the standards that the local governments would have been expected to follow), if these types of data are not readily available from local governments.
    • Asphalt Mix Binder Type, Dowel Bars, Joint Spacing: Add a separate HPMS table to collect Statewide defaults by functional class.
    • Sub-grade AASHTO Soil Type: FHWA would code from maps while allowing States to override.

Freight Related Data Issues


  1. Truck Volume Data

    Since states already collect this information to meet the TMG guidelines that 30 percent of all volume counts should be classification counts, the requirement would be to report the actual truck AADTs for two categories of trucks, single unit and combinations. The percent single unit and combination trucks during the peak hour would continue to be reported for all sample sections. The vehicle classification categories on the HPMS Summary Form will be redefined to agree with the single unit trucks definition of categories 4-7.

    States would be required to report average truck volumes that represent average conditions for that location. This means that the actual truck counts obtained would need to be adjusted just as volume data is adjusted to represent average conditions or an AADTT as promoted in the 2001 TMG. States would be allowed to use existing procedures or may need to develop an interim process to adjust raw truck count data to represent average conditions until their traffic monitoring programs have collected sufficient data to calculate reliable AADTTs.

    Research may be needed on a process to easily calculate truck AADTs, to standardize peak hour definitions, explore use of ITS technology, and relevance to truck commodity surveys.

  2. Truck Forecast Data

    This additional data collection activity would not be added to HPMS reporting requirements. Other sources of this data would be used by those that have a need for it from State procedures. Another option would be to use either the State’s process or the values used by their pavement design section to estimate future axle loadings derived from existing truck loading information to estimate future truck traffic.

  3. Truck Parking

    Information on truck parking facilities may be available from other sources, such as Rand McNally, and would not be added to HPMS. Other databases and publications illustrating locations and descriptions of truck routes and other information useful to truckers may be a source of truck parking information.

Capacity Related Data Issues for HPMS Reassessment


  1. Highway surveillance systems
    There are other sources of information for this data besides HPMS that should be used. These data items would be deleted from HPMS.

  2. Capacity calculations

    Overridden capacity values may already exist at the state or may need to be a separate calculation. The edit routines in the submittal software would be changed so that the V/SF calculations of less than 1.4 would be acceptable as accurate data. States would be asked to explain their process for calculating capacity and the override values reported in HPMS.

  3. K and D factors

    It appears that coding K and D factors is not an issue for States since this data is readily available from existing databases including many off State system locations. States are encouraged to continue using existing procedures for collecting this data based on guidance from the Highway Capacity Manual and other documents. Since capacity is usually not an issue on lower functional classes, estimates currently being used appear to meet the user needs. It is recommended that there be no change in the collection and coding of this data for HPMS.

  4. Widening feasibility

    Since this is already a data item, a better description of how to code it would be developed for both data collectors and data users. The number of lanes that could be added would still be coded and if widening is not feasible, then code the features that are an obstacle to widening.

    Information would be developed on the cost to widening, which features could be eliminated to allow widening, and the cost to eliminate these features. States would identify obstacles within a specific distance from the roadway that would greatly complicate widening, and report this condition as a separate data item.

  5. Counter-peak lanes

    This would be a new data item to add the number of lanes in the counter-peak direction.

Boundaries and Functional Classification


  • Allow options for updating urban and urbanized areas and air quality boundaries
  • Revise functional classification codes to eliminate separate urban and rural classifications (please note the rural, small urban, and urbanized area designation is kept as a separate item)
  • Allow designation of Other Freeways & Expressways in rural and as an option Minor Collectors in rural
  • Update the guidance and provide additional training
  • Develop functional classification for non-centerline facilities (discussed in Interchanges paper)


HPMS needs to evolve towards a geo-spatial data submission format in which HPMS data records are linked to a well-defined geo-spatial highway network base map: therefore, many of the geographic identifier fields in the current HPMS record will become unnecessary. Geo-spatial analysis tools will be further developed to allow the data to be selected and summarized by any geographic area. CAUTION: Geo-spatial (i.e., GIS) analysis techniques enable spatially referenced data to be summarized by any geographic area, as long as that area has well defined geographic boundaries, represented in a geo-spatial database. Additional efforts would be best spent to assist States that were unable to reach a satisfactory level of geo-spatial reporting.

Adjustments to the latest Census-defined urban and urbanized area boundaries would be optional by State. The minimum default boundaries would be the most recent Census-defined urban and urbanized area boundaries. If a State chooses to adjust boundaries, then it would be given a very tight schedule (TBA) for submitting them following the release of information from Census.

After a grace period (TBA) and with no submittal of revised boundaries since the last decennial Census, FHWA would proposed to use the latest Census-defined urban and urbanized area boundaries to bump out existing adjusted urban and urbanized area boundaries as well as to define any new small urban or urbanized areas in order to prepare the HPMS data for purposes such as Highway Statistics, performance trends, etc. One of the HPMS goals is to maintain consistency of definitions for performance trends and Highway Statistics as well as use by the general public.

States that submit their HPMS data using a geo-spatial format would not be required to report the following data items on each HPMS record: Donut Sample (Item 7), Rural/Urban Designation (Item 13), Urbanized Area Code (Item 15), Nonattainment Area Code (Item 16). These data items, along with Urban/Rural and Nonattainment Area expansion factors, would be calculated automatically by FHWA as part of the HPMS data preparation process. Those States that do not submit their HPMS data using a geo-spatial format would continue to code these geographic identifiers in each HPMS data record.

Functional Classification:
Functional System Code Code
Principal Arterials:  
Interstate 1
Other Freeways & Expressways 2
Other 4
Minor Arterials 6
Collectors (Major) 7
Minor Collectors 8
Locals 9

Functional Classes (Item 17) would be consolidated to eliminate the distinction between urban and rural classes (i.e. a segment could be coded as “minor arterial”, not “urban minor arterial” or “rural minor arterial.” Classes could be reduced to only Interstate, Other Freeways & Expressways, Other Principal Arterials, Minor Arterials, Collectors (Major), Minor Collectors, and Locals. The Major Collectors in rural and Collectors in urban would be combined under one code. Those States that do classify public roads as Minor Collectors could as an option report them as Minor Collectors in HPMS. Any public roads not classified as Arterials or Collectors would be classified as Locals.

States would classify all the facilities that are considered Freeways & Expressways in urban and rural. The rural/small urban/urbanized area information would be reported in the Rural/Urban Designation Item or as part of the geo-spatial code.

Update the Functional Classification Guidance and applicable administrative instructions and provide the appropriate functional classification training to staff.

The generated functional system (Item 18)would be dropped.

Any decision for reporting the non-centerline facilities, i.e., ramps and other intermittent auxiliary roads, as well as number of lanes and AADT on them would be stated in the Interchanges paper. Development of some functional class guidance for coding of non-centerline auxiliary facilities may be considered if such facilities are to be reported (see Interchanges paper). No decision has been made to add any other private roads, except those that already are considered as public roads because they serve the public, i.e., toll facilities that operate under the State’s or local government’s blessing.

Process Improvement Background Paper



The pavement metadata that are being proposed describe the processes used for collecting and reporting the IRI data. These data would need to be expanded if additional pavement data items are added to HPMS. Also, if the IRI requirements are changed, some of these data items could be eliminated. It has been proposed that the following data items be optional with the submittal of the 2006 HPMS data in June 2007 and required for the data reported in 2008 and beyond:

  • Type of vehicle (sonar, multi-laser, scanning laser, other)
  • Inclusion of structures
  • Inclusion of railroad crossings
  • Measurement wheel path
  • Measurement lane
  • IRI simulation (half-car, quarter-car, other)
  • Adherence to provisional standard AASHTO PP37-04 (yes, no, partially)

    Like the pavement metadata, the reporting of traffic metadata would also be optional in 2007 and required in 2008 and beyond. These data primarily look at compliance of the State’s traffic data collection processes with those outlined in the Traffic Monitoring Guide (TMG) and the Traffic Management Systems for Highways (TMS/H) guidance produced by FHWA.

  • Current years data — all sections updated
  • Traffic program meets TMS/H requirements
  • Use of short-term counts (< 48 hrs.)
  • All sample sections counted at least once every three years
  • Process in place to verify data, including local data where used

Government Ownership Code

Finally, it is being proposed that the Governmental Ownership code be changed to match the coding of Ownership in the NBI. Governmental Ownership would be changed from a one to two digit field with the following coding options:

01 — State Highway Agency 63 — Bureau of Fish and Wildlife
02 — County Highway Agency 64 — U.S. Forest Service
03 — Town or Township Highway Agency 66 — National Park Service
04 — City or Municipal Highway Agency 67 — Tennessee Valley Authority
11 — State Park, Forest, or Reservation Agency 68 — Bureau of Land Management
12 — Local Park, Forest, or Reservation Agency 69 — Bureau of Reclamation
21 — Other State Agency 70 — Corps of Engineers (Civilian)
25 — Other Local Agency 71 — Corps of Engineers (Military)
26 — Private (other than railroad) 72 — Air Force
27 - Railroad 73 — Navy/Marines
31 — State Toll Authority 74 — Army
32 — Local Toll Authority 75 — NASA
60 — Other Federal Agency (not listed below) 76 — Metropolitan Washington Airports Service
61 — Indian Tribal Government 80 — Unknown
62 — Bureau of Indian Affairs  

Toll Facility Identifier

The FHWA Office of Highway Policy Information will develop the toll facility codes as part of developing the new data model, and published in the 2007 Toll Facility Report. Data on toll facilities are proposed to be collected in a separate table in HPMS as outlined in the new data model. Each toll facility will be represented as single record with a beginning and ending LRS, and the toll facility code.

Data Quality Background Paper


A few of the recommendations voiced by the state DOT’s and FHWA are listed below regarding data quality for new data elements and existing data.

New Data Model

State DOT’s are hoping that the use of already-existing GIS-based databases from each state will allow for a smoother transition for the new data requirements. The pilot program, which is described in the Data Model issue paper, along with input from a team of State GIS and HPMS staff should help insure that the new data model will not be extensively burdensome for most States.

Field Manual

The guidance to the States in the HPMS Field Manual appears to be the source of some data consistency and quality concerns. The Office of Highway Policy Information will work with the data users and data providers to rewrite the Field Manual as part of the HPMS Reassessment. The revised Field Manual will employ additional, more detailed descriptions and where appropriate, more illustrations. Whenever possible, actual State examples will be incorporated. A team of data users and State data providers will be put together to rewrite the manual. The target completion data for the new Field Manual is December 2007.


Each state DOT will continue to work with their District offices and data collection contractors to guarantee that the data is collected correctly and timely and is input properly for submittal.

The new risk assessment based HPMS Field Reviews will be conducted by FHWA Division Offices on an annual basis. These reviews will focus less on reviewing actual data and more on the data collection and reporting processes. Staffing and SPR program reviews will also be included in these reviews. The detection of possible program deficiencies will trigger a more in-depth process review. The results of the Field Reviews are to be submitted to the Office of Highway Policy Information by November 1st.

Data Validation

FHWA will continue to improve its validation software to make certain that invalid data does not appear within any field in the database (e.g., a 4 is not coded in a field with valid inputs of 1, 2, or 3). FHWA will also work with users of the HPMS data to determine if/what invalid data may be appearing in the database that is sent to the users.

The role of the validation software should be reviewed, especially in light of the data falsification that appears to be taking place in order to resolve data verification errors. The verification software is intended to improve data quality, but it appears that in some instances it is doing just the opposite. FHWA needs to determine the extent to which this is happening, and if there is anything that can be done at the administrative level to alleviate this. This appears to be as much an education and outreach issue as it is a data validation issue.

New Data Model


There are two possible approaches to disaggregating the current HPMS submittal file that have been discussed in the outreach workshops and in subsequent webinars. While there are some subtle differences between the two approaches, they both are essentially the same and both would employ the same data model. The first would create multiple tables within the HPMS submittal similar to the current table that States submit. These tables would be functionally grouped, comma delimited files. These files would then be combined through a process known as dynamic segmentation within the HPMS software using the State provided geospatial networks and the State’s LRS. The uniformity of the LRS across the tables would be critical for this method to be successful. An advantage of using comma-delimited files is that the existing HPMS software, especially the Oracle database, would not require major changes. As the Reassessment has progressed, this previous statement has proven to not be entirely correct. While it is true that converting the HPMS database from a flat-file database to a geospatial database would be a sea change, both would require about the same level of effort. It appears at this time that converting the database to a geospatial database would provide benefits exceeding any extra costs that might be incurred.

Currently, LRS is only collected on Principal Arterials and the NHS. It is being proposed that this would be expanded to include all functional classes through rural Major Collector and urban Collector, since this would cover all roads that are eligible for federal funds. The States’ geospatial networks would also need to include all these roads. It was initially thought that this might be a concern for some States, especially for those sample sections off the State network, but in the workshops and webinars most States indicated that they have a complete geospatial network or networks through Major Collector. A couple of States indicated that they have two separate networks, one for State system roads and the other for off-State system roads. The HPMS software and database would probably be able to handle two networks and data for one State, but this will need to be explored further in the pilot.

The second approach that is being considered would allow States to submit their HPMS data as a GIS file or geospatial database with multiple layers; each layer representing a logical grouping of data (pavement, traffic, ITS etc). As previously mentioned, from the FHWA perspective, this is the desired approach. Most States indicated that they would be supportive of providing the HPMS data in a GIS format; with most agreeing that this is probably the best method to employ for future data submittal. However, there were a few States that indicated that they would have trouble linking data for sample sections off the State highway system to their existing State network. Additionally, there are a couple of States that currently would not be able to provide data in a GIS format. Most, if not all of these States did indicate that changing HPMS to a GIS format might provide the impetus that they need to develop a State GIS system, which most seemed to feel was desirable.

Figure 1 - Data Model

Graphic showing the flow and use of the various types of data in the new HPMS data model.

It’s possible to implement this approach while still allowing States to submit their data in the current format. Depending on how the HPMS database is structured, the submittal file could be used as submitted, or it could be disaggregated. The possibility also exists for States to submit a disaggregated file for the sample and universe sections on the State highway system along with a second file, in the current format, for those sample sections off the State highway system. This would be more complicated to implement within the HPMS software and database, but would likely be easier for many States since these data for the HPMS sections off the State highway system often only exist in the State’s HPMS database, and not in the State’s separate management systems. This will have to be explored as part of the pilot.

The Submittal Package

Graphic showing the different event tables in the HPMS data model along with the data items in each table.

The submittal package would include a geometry file in the form of a shapefile or other acceptable format that has measured and calibrated routes. The package would also contain a series of event tables. These tables would contain the core of the HPMS data that would link to the geometry file. For example, the Lanes table will have a record that has the LRS, BEGIN_LRS, END_LRS, THROUGH_LANES, and TYPE_FACILITY. The LRS field would serve as a common identifier that would be used for linking all data tables and attaching them to the State provided geospatial network.

The submittal package would also contain a Global Information which would include information that applies to every record such as Units, Year or Data, Summary data etc. This would also include the comment letter and submittal history information.

While States are welcome to use an existing public or commercial network, FHWA is not at this time considering using a single network (TIGER, Commercial) to create a national backbone network. The benefits of using State provided networks out weigh the costs associated with creating and maintaining a national backbone network. While FHW does have a business need for a routable national network, the primary geospatial need is for State networks that can be used for integrating various datasets and for performing data analysis at the State level and national level. Since States are already maintain a geospatial network for their own business needs, it makes sense to modify HPMS to use these networks rather than duplicating this effort at the national level for a very minimal increase in geospatial data analysis and reporting capabilities.

The following are the requirements for the State geospatial networks. It should be noted that these recommendations take into consideration the comments provided by the data users and data providers in the Reassessment workshops and webinars. At this time, FHWA is not prepared to further define the many other “attributes” of the State geospatial networks. The State pilot will attempt to identify those network attributes that need to be standardized in HPMS. Data providers and data customers not involved in the State pilot are encouraged to submit their recommendations on additional network standards.

  • Scope — It is recommended that the State supplied geospatial networks be dual carriageway. The State pilot should consider if this could be a phased implementation that would allow States with single line networks time to develop a dual carriageway network. A dual carriageway network will ensure that the HPMS data and the associated networks will be linkable with all data sets. States will need to indicate the inventory direction in their metadata.
  • Extent — The State supplied geospatial network will need to include all roads through rural Major Collector and urban Collector both on and off the State highway system. For those States that maintain the roads functionally classified below rural Major Collector and urban Collector in their State network, these systems can also be included in their HPMS submittal and do not have to be taken out.
  • Accuracy — It is desirable that the State supplied geospatial networks have an accuracy of 1:10,000, although networks up to 1:24,000 will be accepted. Through the survey of State GIS staff at GIS-T, 50% of the States indicated that their networks have an accuracy of 1:10,000 or better, with all but three of the responding States indicating that they have a network with an accuracy of 1:24,000 or better.
  • Interstate Connectivity — While there are offices within the FHWA that require a routable national network, it is anticipated that the previously mentioned research project will result in a method that can be used to convert the individual State networks into a routable national network; this should address the State-to-State connectivity need of all FHWA users. The connectivity of the data to the network will be through the States’ own LRS.
  • Intrastate Connectivity - States are encouraged to use an LRS for HPMS reporting that is consistent with the LRS being used for all other federal data reporting. Through the HPMS Reassessment, FHWA is proposing “one network and one LRS for all Federal data reporting.” This theme has been widely embraced by most States and most if not all of the Federal agencies engaged through the Reassessment.

Maintenance — The proposed data model will use the State supplied geospatial networks, which need to correspond to the HPMS data being submitted that year. To insure a 100% match between the HPMS data and the geospatial network, States are encouraged to submit a new network every year.

Sampling Background Issue Paper


Below is a summary and discussion of various recommendations and options for consideration in the current HPMS reassessment effort or for future consideration and study. The basic sampling scheme for HPMS is not recommended for significant change at this time. Below are three sections into which the issues are separated: Immediate implementation is applicable only to #1 below, short-term study is applicable for #2 (completed by September 2007), and long term study is recommended for the remainder until which time a further/future in-depth study can be made.

Immediate Implementation

Universe/Summary AADT: Present scheme of sampling within urbanized areas, small urban areas, and rural by functional system and by volume strata could be retained (a study proposal should be scheduled for a future years when more research monies would be expected to be available). The State should report estimated AADT’s at least within a special study area(s) to populate the rest of the Minor Arterials and Collectors (Major) universe not already reported with AADTs (Data Item 33) for any NHS or STRAHNET or standard sample segment in order to avoid having to develop donut areas and add donut samples. If this would be an acceptable option, the Donut Area Sample AADT Volume Group Identifier (Item 31) as well as the entire donut sampling procedure could be deleted. FHWA also proposes to include AADT (Item 33) as a required item for all reported Federal-aid highway segments. Inclusion of AADT for all Minor Arterials and Collectors (Major) segments would greatly simplify the estimation of VMT for specific geographic areas as well as nonattainment or maintenance areas by pollutant. Currently, only the standard and donut samples required AADTs to be reported on all Minor Arterials, rural Major Collectors, and urban Collectors. Please note that AADT reporting was already required on a universe basis for all Principal Arterials and NHS and STRAHNET and samples on Minor Arterials, rural Major Collectors, and urban Collectors.

The current Summary Template used for the air quality nonattainment & maintenance areas would be modified to accommodate reporting a combined estimate of DVMT for the lowest systems by area and pollutant; these lowest systems would include any rural Minor Collectors and rural/urban Locals located within the nonattainment or maintenance area. The Donut scheme would be deleted in favor of reporting estimated AADTs in special study areas to populate the rest of the AADT cells on the minor arterials and collectors (major) segments that are not already samples or part of the NHS or STRAHNET.

The statisticians need to make a recommendation how to keep the sample panel representative of the entire urbanized area in cases where large additions are added to an existing urbanized area sample panel. The Urbanized Area Sampling Technique (Item 14) would be dropped. A decision needs to be made regarding allowance of sub-area sampling within a large urbanized area.

  • Item 7 -- Is Donut Sample — eliminated
  • Item 14 -- Urbanized Area Sampling Technique — eliminated
  • Item 31 -- Donut Area Sample AADT Volume Group Identifier — eliminated
  • Item 33 -- AADT — estimated AADTs would be allowed to populate the minor arterials and (major) collectors at a minimum for nonattainment/maintenance areas that are not on a sample, NHS, or STRAHNET
  • Item 48 — Donut Area Sample Expansion Factor — eliminated

    Short Term Study

    AADT volume group strata adjustment: FHWA proposes establishing a single AADT Volume Group (Item 32) stratification that would apply across all geographic area types (i.e., rural, small urban, urbanized, nonattainment, etc.) The suggested AADT volume group strata shown below should be evaluated to determine the impact of various options (i.e., wider volume ranges as the volume increases, use same volume ranges across urban/rural, etc.). AADT volume group strata adjustment should be tested to determine the impact of various options (i.e., wider volume ranges as the volume increases, use same volume ranges across urban/rural, etc.). The expectation is that this change has the green light. A generic set of common AADT Volume Groups is recommended. Adjustments in volume ranges might be made if the studies confirm further change is needed.

    AADT Volume Groups Code
    Under 500 1
    500 — 1,999 2
    2,000 — 4,999 3
    5,000 — 9,999 4
    10,000 — 19,999 5
    20,000 — 34,999 6
    35,000 — 54,999 7
    55,000 — 84,999 8
    85,000 — 124,999 9
    125,000 — 174,999 10
    175,000 — 249,999 11
    250,000 and more 12
  • Item 32 — Standard Sample AADT Volume Group Identifier -- Common generic AADT Volume Groups

    Long Term (Future) Study

    National sample: Further exploration of obtaining additional items on a sample basis for the non-Federal-aid Highways would be looked at most likely on a case study basis. No final decision has been made.

    Alternative sampling methods: Alternative variable schemes, if viable, could be reviewed and proposed. Levels of precision needed for FHWA purposes need to be visited, since the level of precision directly affects the amount of samples required. If a commitment is made, than criteria would be very helpful in deciding the alternative schemes as well as the appropriate levels of precision to employ.

    NHS sample: A NHS sampling scheme by State would be implemented using the existing standard samples supplemented with extra standard samples where needed. A separate Item would be retained for the NHS expansion factor as like the standard sample expansion factor. An in-depth analysis is needed to verify the proposed results. Also, a decision would need to be made whether to sample on the NHS Locals and Rural Minor Collectors. A final decision should be made regarding the scheme and levels of precision. Nobody has stated which HPMS Items would be applicable with the National sampling scheme; this needs to be worked out.

  • New Item — NHS Expansion Factors (applicable to the non-Interstate parts)

    Geospatial expansion factors: When the results of a study of allowing expansion factors to be created separately for each set of items reported by a particular shop are available, then appropriate decisions can be made.

  • Item 16 — NAAQS Nonattainment/Maintenance Code (option) -- These items would not be needed for States that submit HPMS using a geospatial format — It could include up to 6 possible pollutants using the EPA-named area name (entry means yes the segment is within the affected area).

    Sample size formula: No decision has been made of the exploration of the sample size formula and how it is used to calculate the required sample size within each volume group. Logically, it should be considered early if some fine tuning adjustments are to be taken.



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