Highway Performance Monitoring System Field Manual

for the Continuing Analytical and Statistical Database

Chapter 4 - Universe and Sample Data Requirements

Universe Data

Certain basic inventory information is required to be reported for all open-to-traffic, public road systems in the universe portion of the HPMS data set (Items 1-46). The total length reported for all open-to-traffic records should agree with the Certified Public Road Mileage. Limited universe data for facilities on planned National Highway System (NHS) roadways that are not yet built or open to traffic also are to be reported. Universe data must be reported on a section-by-section basis for all rural arterials, urban principal arterials, the NHS and all standard sample and donut area supplemental sample sections; universe data may be reported for the remaining functional systems on a grouped length basis.

Standard Sample Data

Additional detailed information is required for a statistically chosen sample of roadways on major functional systems. The sampled functional systems include all but the rural minor collector, rural local, and urban local systems. The additional detailed data are reported for the standard sample portion of the HPMS data set (Items 47-98). The standard sample is intended to represent all applicable systems both on and off the State highway system. The standard sample is used for a variety of purposes including performance measurement, investment requirements modeling in support of Condition and Performance Reports to Congress, policy, other analyses, and in various publication media.

Donut Area Sample Data

An additional sample is required for the donut area portions of NAAQS nonattainment and maintenance areas that use the HPMS as the basis of VMT estimates for air quality travel tracking and conformity purposes. The donut area supplementary sample consists of sections in the rural and small urban minor arterial, rural major collector, and small urban collector functional systems that are located outside of urbanized area(s), but within the nonattainment or maintenance area boundary. The donut area supplementary sample is used to enhance the existing standard sample to achieve higher confidence levels for travel estimates. The purpose of the donut area supplementary sample is limited to the development of travel estimates. The combination of existing standard samples in the donut area plus the donut area supplementary samples makes up the donut area sample.

In addition to the universe data items, donut area supplementary sample sections need only have sample data Items 47 and 48 coded.

Coding Nonuniform Roadways

The HPMS is an inventory system that requires reported data to represent both directions of roadway condition and operation. As a result, conflicts in data item coding may arise for specific data items under certain reporting conditions. The following provides some guidance in addressing conflicts.

Data items that involve widths, types, condition, etc., may differ in shape or dimension on each side of a roadway. To resolve this, choose one side of the facility for inventory purposes and code only the applicable data items for the chosen side of the highway. This should be done for all roadways, whether divided or undivided with common or independent alignments. The "inventory direction" should be chosen on a statewide basis (i.e., always South to North, East to West, or vice versa) and once selected never changed.

Some data items such as AADT, number of through lanes, median width, etc., reflect the complete two-way facility. Exercise extra care when reporting through lane counts and AADT because these data are used for apportionment purposes.

Appendix E requires IRI to be reported for the same direction and lane all of the time. The "inventory direction" of a facility should be used as the side where IRI is measured and reported. IRI should not be reported or averaged for both sides of a roadway.

Averages can be used for some dimensioned items that change back and forth over a section length (i.e., median width, shoulder width). In situations where a condition changes back and forth between two or more possible types over the section length, the predominant condition can be reported (i.e., shoulder type, surface type). In both cases, the lesser or worse measurement or condition for the roadway section can be reported instead.

If one part of an existing section becomes very different from the other due to a change, for instance, in the number of lanes, urban/rural break, new construction, etc., the predominant condition cannot be reported and the existing section may need to be split. A full discussion of this topic and a list of the changes that require sample splitting can be found in Chapter VII.

Structure Treatment

The total length of all public roads, including structures, must be represented in the HPMS; note that a ferryboat is not a public road and should not be reported in HPMS. Where structures are a part of a universe or standard sample section, the reported data items should reflect the off-structure roadway conditions. However, since the HPMS standard sample is intended to represent the off-structure roadway and its conditions, standard sample sections that exist entirely on structures should be avoided if at all possible. Structures should be used as standard samples only when a volume group sample size requirement cannot be satisfied without inclusion of a structure-only section and the section cannot be combined with a roadway section.

Existing standard sample sections totally on structures should be eliminated in favor of standard sample sections on off-structure roadways where possible. Alternately, on-structure standard samples can be combined with adjacent roadway sections and the roadway characteristics reported in HPMS. When choosing new standard samples, delete any sections that are totally on structures from the list of candidates.

When a section is entirely on a structure, only the following data items need be reported, as applicable:

Code all other data items "0" or "0.0" as appropriate. Supplementary donut area sample sections that are totally on structures are permitted.

Planned Unbuilt Facility

Limited data for unbuilt facilities are included in HPMS for NHS routes only. Unbuilt facilities should only be included if there are plans for the route to be built. For unbuilt sections, only universe data items 1-19 and 30 are required.                       

General Reporting Requirements

The HPMS data are used for a variety of purposes ranging from apportionment of highway funds to public information; therefore, the use of a data item governs the HPMS required coding. Although reporting agencies may have a need for highway inventory data coded differently from the HPMS, the State's highway inventory data system must nevertheless be capable of providing the HPMS data according to the coding requirements contained in this Manual. If there is not a one-for-one relationship between the State data inventory system and the HPMS coding requirements, the State may need to obtain additional data, revise its inventory data coding to match the HPMS, or provide means to aggregate, disaggregate, or convert State inventory data into data that meets HPMS coding requirements. Where the State has a need for a data item or some physical attribute that is not needed for HPMS, the data can be retained in the State's inventory system.

Data Item Summary Table

In the following data item summary tables (Tables IV-1 and IV-2), an "A" indicates that the item is required for all universe, standard sample, and supplementary donut area sample sections; an "S" indicates that the item is required only if the section is a standard sample; and a "D" indicates that the item is required only if the section is a supplementary donut area sample. A blank indicates that the data item is not coded for the functional system. The following abbreviations are used in the column headings.

Do not rely solely on the data item summary table for data coding requirements. A number of data items require additional discussion regarding the type of section to which the data coding applies. For example, although the summary table indicates that Percent Passing Sight Distance (Item 78) is required for the rural standard sample sections, it is required only for rural paved, two-lane facilities.

[1] The "A" in the summary table cells for the Donut Area Volume Group (Item 31) is meant to indicate that all data records (universe only and sample) for the noted functional systems in a donut area are to include these data.

General Coding Instructions

Data items in the summary table are denoted in the Data Type column as having either "numeric" or "character" reporting specifications.
For numeric data items:

• leading zero must be coded in decimal value when the value is less than an integer (length = 0.21); otherwise, leading zeros are not required
• decimal points are required for all data items labeled "Numeric; Decimal," i.e., those reported in tenths, hundredths, or thousandths (PSR = 2.2; length = 10.252, etc.)
• one digit must be coded after a decimal point for all data items labeled "Numeric; Decimal"
• (PSR = 3 must be coded 3.0); additional trailing zeros are not required for the decimal portion
• when data is not available, code "0" or "0.0" as appropriate

For character data items:

• any alphanumeric character (A through Z; 0 through 9; space) may be coded
• do NOT use double quotes (") within the character string

For data items with assigned values (codes):

• select the appropriate value from the table
• the value must be coded precisely as listed in the table

Data Coding Instructions

Item 1 — Year of Data (Numeric; Integer)
Enter the four digits of the calendar year for which the data apply. The HPMS software is "year 2000" compliant.

If adding a section while working in the HPMS software, the year will automatically be set based on the year in which the user is working. The year is displayed on top of the screen.

Item 2 — State Code (Numeric; Codes)
The State FIPS code is used in the HPMS database to identify the reporting State. Enter the State FIPS code as listed in Appendix A.

If adding a section while working in the HPMS software, the State code will automatically be coded based on the State selected. The State name is displayed on top of the screen.

Item 3 — Reporting Units - Metric or English (Numeric; Codes)
Code for all sections to indicate the units used to report measured and other measurement related data items. All data submitted to FHWA must be in metric units; the HPMS software will automatically convert all data to metric during the FHWA submit process. The same reporting unit must be used for all applicable data items for the entire data set. There can be no mixing of units within the data set.

Reference: American Association of State Highway Transportation Officials (AASHTO) Guide To Metric Conversion, 1993

Hard conversion of data Items 54 (Lane Width); 59 and 60 (Shoulder Width); 79 (Weighted Design Speed); and 80 (Speed Limit) is preferred. A soft conversion for data Item 35, Measured Pavement Roughness, is provided in Appendix E as 63.36 inches/mile = 1.0 meter/kilometer.

HPMS conversion software is discussed in Appendix L; the software will perform the appropriate conversions of all of the applicable data items from English to Metric.

Item 4 — County Code (Numeric; Codes)
The FIPS county code permits analysis and mapping of information at a sub-State level. Enter the three-digit FIPS county code from FIPS Publication 6-4, Counties and Equivalent Entities of the United States, Its Possessions, and Associated Areas. Use county equivalents in HPMS for the following:

In the HPMS software, the County Names table must be kept current. To add a county, modify a county name, or delete a county code, select "Tools/County Names." When adding a section, the county code must be in the County Names table or the system will not allow the section to be added.

Item 5 — Section Identification (Character Field)
This item permits locating specific roadway section data within the HPMS database. This item must contain a 12-character countywide unique identifier. It provides flexibility to identify sections in accordance with a State's needs independent of the unique identifier that must be maintained for sample sections. This item may be defined to suit the needs of the State and may contain any right-justified alphanumeric character.

• For all individually reported sections (code "0" in item 9), supply a countywide unique section identifier. This may be a location specific identifier such as route kilometerpoint (milepoint), A-node/B-node, or a unique number.
• For highways reported as grouped sections (code "1" in Item 9), provide a countywide, unique group identifier. REMINDER: Only nonsample urban minor arterial, collector and local, and nonsample rural major and minor collector and local data can be grouped; NHS routes cannot be grouped regardless of functional system.

Examples:

1. Section Identifier  (Item 9 = 0)
   Use any countywide unique identifier with no more than 12 "right justified" characters. An example using a location specific identifier:

   Interstate Inventory Route 56, Kilometerpoint 4.321

   Code	0	0	0	I	5	6	0	0	4	3	2	1

2. Grouped Length (Item 9 = 1)
   Use any countywide unique identifier - no limit on number of digits. An example using a unique number:

   Grouped Length Record 98365

   Code	0	0	0	0	0	0	0	9	8	3	6	5

Item 6 — Is Standard Sample (Numeric; Codes)
This data item is used by the software to indicate if a section is a standard sample.

Item 7 — Is Donut Sample (Numeric; Codes)
This data item is used by the software to indicate if the section is a donut sample.

If a section is:

• a universe section only, code "0" for both Items 6 and 7;
• both a standard sample and a donut sample, code "1" for both Items 6 and 7;
• a donut sample, code "0" for Item 6 and code "1" for Item 7;
• a standard sample, code "1" for Item 6 and code "0" for Item 7.

Item 8 — State Control Field (Character Field)
This is a data item of up to 100 alphanumeric characters for State use for identification or any other purpose. It may contain any keyboard characters; however, do not use binary zeros or double quotes. FHWA does not use this data item.

Item 9 — Is Section Grouped? (Numeric; Codes)
This item is used by the software to indicate whether the data reported are for a single section or for a group of sections.

Use code "0" for all sections, including universe, standard sample, and supplementary donut area sample sections that are being reported on an individual section basis. Code "0" must be used for all principal arterial system (PAS), rural Minor Arterial, and NHS sections - grouping within these systems is not permitted.

Use the grouped length code "1" only when grouping homogeneous sections for reporting purposes; contiguous sections should not be reported as grouped sections. Only nonsample rural major collector, rural minor collector, rural local, nonsample urban minor arterial, nonsample urban collector, and urban local system sections not on the NHS can be grouped. Grouping may only be done when the data for Items 4; 13-17; 25-29; and 31-32 are homogeneous across all sections being grouped.

Item 10 — LRS Identification (Character Field)
This item, along with Items 11 and 12, permits users to reference HPMS information to the map location of road sections. Code for all PAS, NHS, and rural minor arterial system sections, in conjunction with LRS beginning and ending points (Items 11 and 12). More information concerning the LRS may be found in Chapter V, Linear Referencing System Requirements.

Inventory Route and Subroute Numbers for LRS Use:
The inventory route and subroute numbers reported in this item must be consistent with the inventory route and subroute numbers identified on the Inventory Route and Node Maps and in the Inventory Route Link Data File discussed in Chapter V, Linear Referencing System Requirements.

The inventory route number is a 10-character, right justified value. The LRS inventory route number can be alphanumeric, but must not contain blanks; leading zeros must be coded. The inventory route number is not necessarily the same as that posted along the roadway, but is a number used to uniquely identify a route within at least a county or, alternately, throughout the State. The inventory route number is followed by a 2-character numeric subroute number that uniquely identifies the AHEAD and BACK portions of an inventory route section where duplicate kilometerpoints (KMPTs) [milepoints (MPTs)] occur.

Item 11 — LRS Beginning Point (Numeric; Decimal)
This item, along with Items 10 and 12, permits users to reference HPMS information to the map location of road sections. Code this item for all PAS, NHS, and rural minor arterial system section records for the purpose of establishing an LRS. This numeric item must be coded with the beginning KMPT (MPT) for the section on the inventory route and for the subroute number coded in the LRS Identification (Item 10).

The KMPT (MPT) for the section must be consistent with the LRS information found on the Inventory Route and Node Maps and in the Inventory Route Link Data File for a particular route and subroute. In order to be consistent, section breaks must adhere to the conditions listed in Chapter V, particularly under the section titled "Effects of LRS on HPMS Sections." See Chapter V for a full discussion on coding of the Linear Referencing System.

Code "0.0" for this item if LRS information is not provided. Code the beginning KMPT (MPT) to three decimal points. The KMPT (MPT) represents the distance in kilometers (miles) from a set reference point to the beginning of the highway segment and is the lowest KMPT (MPT) of the section.

The KMPT (MPT) numbering format should be such that the combination of county, inventory route number, subroute number, and KMPT (MPT) information will define a unique location.
Example: Beginning kilometerpoint 98.252 for the inventory route and subroute number coded in Item 10:

Item 12 — LRS Ending Point (Numeric; Decimal)
This item, along with Items 10 and 11, permits users to reference HPMS information to the map location of road sections. Code this item for all PAS, NHS, and rural minor arterial system section records for the purpose of establishing an LRS. This numeric item must be coded with the ending KMPT (MPT) for the section on the inventory route and for the subroute number coded in the LRS Identification (Item 10).

The KMPT (MPT) for the section must be consistent with the LRS information found on the Inventory Route and Node Maps and in the Inventory Route Link Data File for a particular route and subroute. In order to be consistent, section breaks must adhere to the conditions listed in Chapter V, particularly under the section titled "Effects of LRS on HPMS Sections." See Chapter V for a full discussion on coding of the Linear Referencing System.

Code "0.0" for this item if LRS information is not provided. Code the ending KMPT (MPT) to three decimal points. The KMPT (MPT) represents the distance in kilometers (miles) from a set reference point to the end of the highway segment and is the highest KMPT (MPT) of the section.

The KMPT (MPT) numbering format should be such that the combination of county, inventory route number, subroute number, and KMPT (MPT) information will define a unique location.

Example: Ending kilometerpoint 101.206 for the inventory route and subroute number coded in Item 10:

Item 13 — Rural/Urban Designation (Numeric; Codes)
This item permits analysis and mapping of information at a sub-State level. Code the value best describing the area.

The decennial or special census urban boundary, including portions that cross State boundaries, is used to establish population criteria for coding this data item. County level estimates are available by the end of each calendar year on the Internet at www.census.gov.

Item 14 — Urbanized Area Sampling Technique (Numeric; Integer)
This item is used by the software to calculate expansion factors. All urbanized areas that contain a population of 200,000 persons or more, or smaller urbanized areas that are within an NAAQS nonattainment area boundary, or smaller urbanized areas that are NAAQS nonattainment areas on their own must be individually sampled. This includes any portion of a nonattainment urbanized area that crosses a State boundary, and individual State portions of an urbanized area that, in the aggregate (all States), contain more than 200,000 persons, even if the State's portion does not reach that population by itself.

Code "0" for rural universe and standard sample sections and urban universe and standard sample sections that are located in urbanized areas, which are being individually sampled. For grouped urbanized areas within one Federal-aid urbanized area, a State may code universe and standard sample roadway sections as follows:

If two or more areas are being grouped (assuming each urbanized area is maintained as a separate area), one number, starting with "1," should be used to identify the sections in each group. For example, if a State has consolidated all qualifying urbanized areas (<200,000 population and not an NAAQS nonattainment area) into one group, "1" should be coded for all sections in the group. If qualifying areas have been consolidated into two groups, sections in the first group of qualifying areas should be coded "1", and those in the second group coded "2." Sections in remaining individually sampled urbanized areas should be coded "0."

Item 15 — Urbanized Area Code (Numeric; Codes)
This item permits analysis and mapping of information at the urbanized area level. Enter the numeric urbanized area code for sections within an urbanized area boundary when the Rural/Urban Designation (Item 13) is coded "3" or "4". Otherwise, code "0." Codes are included in Appendix B. Code for universe and standard sample sections only. Leading zeros are not required. If the State chooses to combine two or more urbanized areas into one Federal-aid urbanized area as approved by FHWA, use the code of the most populous urbanized area. In the HPMS software, the Urbanized Area Names table must be kept current.

Item 16 — NAAQS Nonattainment Area Code (Numeric; Codes)
This item permits analysis and mapping of information for EPA designated nonattainment and maintenance areas. Enter the numeric urbanized area code for the EPA-named NAAQS nonattainment or maintenance area for all rural, small urban, and urbanized area universe, standard sample, and supplemental sample sections within the NAAQS nonattainment or maintenance area boundary. When more than one urbanized area is within the nonattainment or maintenance area boundary, enter the code for the most populous urbanized area. Leading zeros are not required.

Code "0" for sections that are not within a nonattainment or maintenance area boundary, or if an NAAQS nonattainment area contains only partial or split urbanized areas. Because the HPMS sample can represent only whole urbanized areas, expanded results are not legitimate for partial urbanized areas and HPMS cannot be used for travel tracking or other air quality purposes in these areas.

Urbanized area codes are included in Appendix B; assignment of NAAQS nonattainment area codes is discussed in Appendix G including in areas that are nonattainment or maintenance for multiple pollutants. The Houston nonattainment area coding example in Appendix G provides more explanation for coding this data item.

Item 17 — Functional System Code (Numeric; Codes)
This item permits analysis and mapping of information by highway functional system. Code the value that represents the functional system upon which the section is located.

Definitions of the highway functional systems can be found in Highway Functional Classification, Concepts, Criteria and Procedures, FHWA, March 1989.

Item 18 — Generated Functional System Code (Software Calculated)
This item is encoded by the HPMS software based on the Functional System (Item 17), and is used as a software aid. If Item 17 is changed, the standard calculations in the HPMS software package must be run to obtain the proper code in this field. The codes are as follows:

Item 19 — National Highway System (NHS) (Numeric; Codes)
This item, along with item 20, is used to track changes to the approved NHS, including intermodal connectors. Code this item for all sections to indicate whether the section is on the NHS or is an NHS connector to an intermodal facility. See the definition of NHS in Chapter II. Enter one of the following codes:

Item 20 — Planned Unbuilt Facility (Numeric; Codes)
This item, along with item 19, is used to track changes to the approved NHS, including intermodal connectors. Code the status of the section being reported.

For sections coded "0" or "1", code all applicable data items. For sections coded "2", report at least items 1-19 and 30, as applicable.

Item 21 — Official Interstate Route Number (Character Field)
This item, along with Items 22, 23, and 24, is used to track HPMS information by specific route. Code for all Interstate System sections using the officially approved AASHTO/FHWA Interstate route number. Enter a 5-character, right justified, alphanumeric value for the Interstate System route number. If two or more Interstate routes occupy the same roadway, code the lowest official route number. If the route is not an official Interstate route, leave blank or zero-fill, regardless of signing.

Alaska, Hawaii, and Puerto Rico may use alpha characters in the Interstate route number field as part of the official AASHTO/FHWA route number. Other exceptions include coding for Interstate routes with parallel or diverging branches having cardinal direction letters in the official route number; for example, Interstate Route 35 in Minnesota splits with 35E going through St. Paul and 35W through Minneapolis.

Item 22 — Route Signing (Numeric; Codes)
This item, along with Items 21, 23, and 24, is used to track HPMS information by specific route. Code for all PAS, NHS, and rural minor arterial system sections. Reporting for other systems is optional. Code the value which best represents the manner in which the highway segment is signed with route markers. If the roadway is unsigned, use code "0."

When a section is signed with two or more identifiers (i.e., Interstate 83 and U.S. 32), code the highest class of route (Interstate in this example). Follow the hierarchy as ordered above.

Item 23 — Route Signing Qualifier (Numeric; Codes)
This item, along with Items 21, 22, and 24, is used to track HPMS information by specific route. Code for all PAS, NHS, and rural minor arterial system sections. Reporting for other systems is optional. Code the value which best represents the manner in which the highway segment is signed on the route marker described in Item 22. Where more than one code is applicable, use the lower code. If the roadway is unsigned, use code "0."

Item 24 — Signed Route Number (Character Field)
This item, along with Items 21, 22, and 23, is used to track HPMS information by specific route. Code for all PAS, NHS, and rural minor arterial system sections. Reporting for other systems is optional. Enter an 8-character, right-justified, alphanumeric value for the signed route number shown on the marker described in Items 22 and 23. If two or more routes of the same class in the hierarchy are signed along a roadway section (i.e., Interstate 64 and Interstate 81), code the lowest route number (Interstate 64 in this example). If Items 22 or 23 are coded "9," code other descriptive alphabetic character prefixes or suffixes abbreviated to 8 characters if available. If Item 22 is coded "0," leave blank or zero-fill.

Item 25 — Governmental Ownership (Numeric; Codes)
This item identifies the road owner and is used in cost allocation studies, to track historic data, and in the national highway database. Code the level of government that best represents the highway owner irrespective of whether agreements exist for maintenance or other purposes. The purpose of this item is to identify the owner of public roads; do not include privately owned roads in HPMS. If more than one code applies, code the lowest numerical value.

For purposes of this data item:

• State" means owned by one of the 50 States, the District of Columbia, or the Commonwealth of Puerto Rico including quasi-official State commissions or organizations;
• County, local, municipal, town, or township" means owned by one of the officially recognized governments established under State authority;
• Federal" means owned by one of the branches of the U.S. Government or independent establishments, government corporations, quasi-official agencies, organizations, or instrumentalities;
• Other" means owned by tribal Nations, or nongovernmental organizations with the authority to build, operate, or maintain toll or free highway facilities.

Item 26 — Special Systems (Numeric; Codes)
This item is used to track changes to the STRAHNET and is used by the Department of Defense (DOD) to identify strategic deployment routes. Code whether an open-to-traffic section is on the STRAHNET or a STRAHNET connector (see definition in Chapter 2). Code all open-to-traffic Interstate System sections "1."

Item 27 — Type of Facility (Numeric; Codes)
This item is used to determine whether a roadway or structure is a one- or two-way operation. It is used in investment requirements modeling to calculate capacity and estimate roadway deficiencies and improvement needs, in the cost allocation pavement model, and in the national highway database.

Use code "1" or "2" as applicable except when the section being reported is entirely on a structure.

• One-Way: A roadway or structure section with traffic moving in only one direction during non-peak period hours. When part of a one-way couplet, report each roadway/structure section independently.
• Two-Way: A roadway or structure with traffic moving in both directions during non-peak period hours.

Item 28 — Designated Truck Route (Numeric; Codes)
This item is used in truck size and weight studies as an administrative identifier to determine whether a section is on or off a truck route designated under Federal regulatory authority. Code this item for all applicable sections described below.

Data Item 28 requires the identification of nationally designated truck routes. These are the routes designated for use by dimensioned commercial vehicles under the Surface Transportation Assistance Act (STAA) of 1982 as identified in 23 CFR 658, Appendix A. Nationally designated truck routes include the Interstate System (a few sections are exempted by Federal law in Minnesota and Virginia), non-Interstate routes specifically listed in 23 CFR 658, Appendix A, as amended, and the other non-Interstate existing Federal-aid Primary (FAP) routes as defined in 1991 that STAA-dimensioned commercial vehicles may legally operate on. These routes are to be coded as "1" in HPMS Item 28.

Some States have allowed STAA-dimensioned commercial vehicles to operate on other State routes. These and other non-national truck network roads used between the STAA national network and terminals and facilities for food, fuel, repairs, and rest under the reasonable access rule are not nationally designated truck routes. These routes are to be coded as "0" in HPMS data Item 28.

Item 29 — Toll (Numeric; Codes)
This item is used as an administrative identifier to determine whether a section is on or off a toll road. Toll data are also used for historic trends, policy analysis, and legislation development purposes. Code this item for all sections.

In general, code a section as toll if a fee is charged for its use. If portions of a contiguous facility can be traversed without the payment of a toll, but a toll is charged on other portions, code the entire contiguous facility as toll. This applies even if some vehicles can enter and exit from the main through route without payment of a toll. If a toll is charged in only one direction, the "free" direction is also considered to be toll. Code a facility operated by a toll authority upon which no toll is charged as non-toll.

Item 30 — Section Length (Numeric; Decimal)
This item provides basic inventory information on the amount of public roads. It is extensively used for apportionment, administrative, legislative, analytical, and national highway database purposes. Code this numeric data item for all sections. Report length, in kilometers (miles), as measured along the centerline of the roadway. If the state has chosen an inventory direction for data reporting on divided facilities, the length is as measured along the centerline of the inventory direction. On independently aligned, divided highways, centerline length also may be reported as the average of the lengths of the directional roadways, measured along their center lines. Report the length of the two roadways of a one-way couplet independently; do not average.

At-Grade Intersections

Figure IV-1. Two-Way At-Grade Intersections.
Length is measured to the midpoint of the roadways.

When measuring length between at-grade route intersections, use the actual center of the intersection as the point of measurement (Figure IV-1). If grade separated, measure to the theoretical center of the intersecting roadways. When a route terminates at a tee interchange, measure the length as the average of the four directional, connecting ramp lengths to the first point of intersection with the other mainline route (Figure IV-2). In all other situations, ramps are considered part of the mainline routes and their length is not reported for HPMS purposes.

When grouping homogeneous nonsample roadways (see Items 5 and 9), code the total combined length of the grouped sections. Code length to the nearest thousandth, although measurements may reflect the precision normally utilized by the State. Minimal measurement precision to at least the nearest tenth kilometer (mile) is requested. Length cannot be zero-coded.

Freeway Connections

Figure IV-2. Freeway Tee Intersection.
Length is an average of the four connectors (Ramps) measured to the gore points.

Item 31 — Donut Area Sample AADT Volume Group Identifier (Numeric; Integer)
This item is used to identify the AADT volume group for a section when an actual AADT is not reported in Item 33. Code a donut area sample volume group number (valid codes 1-5) for the section when an AADT is not coded in Item 33; when an AADT is coded, the HPMS software will assign the volume group number if the State is using the FHWA volume group ranges. The AADT or volume group must be coded for applicable universe, standard sample, and donut area supplementary sample sections for the rural minor arterial and major collector, and the small urban minor arterial and collector functional systems that are within the donut area portion of a nonattainment area. Code "0" for all other sections. The AADT ranges for each volume group number are shown in Appendix C, Table C-5.

When AADT is not known, use traffic flow maps, count data obtained from local governments, and other available data to make reasonable volume group assignments.

A discussion of NAAQS nonattainment and donut areas and a description of the donut area sampling scheme is contained in Appendix G.

Item 32 — Standard Sample AADT Volume Group Identifier (Numeric; Integer)
This item is used to identify the AADT volume group for a section when an actual AADT is not reported in Item 33. Code a standard sample volume group number (valid codes 1-13) for the section when an AADT is not coded in Item 33; when an AADT is coded, the HPMS software will assign the volume group number if the State is using the FHWA volume group ranges. An AADT or the volume group must be coded for applicable universe, standard sample, and donut area supplementary sample sections for all except the rural minor collector and the rural and urban local functional systems.