NMDOT Functional Classification Guidance Manualwhich are the allowable design standards (i.e. speed, horizontal and vertical alignment, etc.). While reviewing the existing functional

New Mexico Department of Transportation (NMDOT)

Functional Classification Guidance Manual

October 2013

(revised February 2014)

NMDOT Functional Classification Guidance Manual

i

Table of Contents

1.0 Introduction ......................................................................................................... 1-1

2.0 Functional Classification Terminology and Uses......................................... 2-1

2.1 Defining Functional Classification ........................................................... 2-1

2.2 Uses of Functional Classification .............................................................. 2-3

Federal Uses of Functional Classification ............................................... 2-3

State Uses of Functional Classification .................................................... 2-6

3.0 Factors Impacting Functional Classification Determination...................... 3-1

3.1 FHWA Guidelines for Mileage and VMT ............................................... 3-2

Mobility and Accessibility ......................................................................... 3-9

4.0 Adjusting Urban Boundaries and Determining Functional Classification ....................................................................................................... 4-1

4.1 Urban Boundaries ....................................................................................... 4-1

GIS Tools for Analysis and Revision of Urban Boundaries .................. 4-2

4.2 Procedural Steps for Determining Functional Classification ............... 4-6

General Rules ............................................................................................ 4-10

5.0 Partners in the Functional Classification Process ......................................... 5-1

5.1 Responsibility for Maintaining Functional Classification ..................... 5-1

A. Glossary ............................................................................................................... A-1

B. References ........................................................................................................... B-1


iii

List of Tables

Table 2.1 Functional Classification Codes ............................................................. 2-1

Table 2.2 Mileage (by State) by Functional Classification and Area Type ....... 2-4

Table 2.3 Public Road Mileage by Functional Classification and Area Type for New Mexico .............................................................................. 2-5

Table 3.1 VMT and Mileage Guidelines by Functional Classification – Arterials ..................................................................................................... 3-3

Table 3.2 VMT and Mileage Guidelines by Functional Classification – Collectors and Locals ............................................................................... 3-4

Table 3.3 New Mexico Functional Classification Guidance – RURAL Road System ............................................................................................. 3-5

Table 3.4 New Mexico Functional Classification Guidance – URBAN Road System ............................................................................................. 3-7

Table 4.1 FHWA Urban Area Types Defined by Population Range ................. 4-2

Table 4.2 Key Milestones for Development and Submittal of the Functional Classification Network ...................................................... 4-11


v

List of Figures

Figure 3.1 Federal Functional Classification Decision Tree ................................ 3-10

Figure 4.1 New Mexico MPO/RPO Boundaries .................................................... 4-5

Figure 4.2 Determining Functional Classification ................................................. 4-7

Figure 4.3 New Mexico Functional Classification Change Request Form ......... 4-9


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1.0 Introduction

This New Mexico Department of Transportation Functional Classification Guidance Manual (2013) describes the procedures, terms, and tools used for analyzing the roadway system in the state of New Mexico for the purposes of determining functional classification of the state’s public road network. This manual was developed as part of the Statewide Functional Classification Review Project in 2013 under the direction of the New Mexico Department of Transportation (NMDOT) Transportation Planning and Safety Division. This edition of the NMDOT FC Guidance Manual was revised in February 2014 to reflect corrected definitions of Minor Collectors and Local Roads in Table 3.4.

The Federal Highway Administration (FHWA) recommends that states review the functional classification of their road system every 10 years (following the decennial Census) and that the review be completed within three years of approval by FHWA of the adjusted urban area boundaries, based on the census urban area boundaries. The functional classification of a road impacts several business decisions at a state Department of Transportation (DOT), not the least of which are the allowable design standards (i.e. speed, horizontal and vertical alignment, etc.).

While reviewing the existing functional classification system, particular attention should be given to recommended functional classification changes for roads on the National Highway System (NHS). Any changes to the NHS need to be coordinated with FHWA’s Headquarters Office of Planning, Environment and Realty. Approval of changes to the NHS occurs at FHWA headquarters, with the procedures for those types of modifications detailed in 23 Code of Federal Regulations (CFR) 470.

The following paragraphs explain the objective, intended use, target audience, and document organization of this manual.

Objective

The objective of this manual is to provide guidance to the NMDOT and its local planning partners (Metropolitan Planning Organizations (MPOs) and Regional Planning Organizations (RPOs)) in evaluating and determining the appropriate functional classifications for the public road system in the state.

Intended Use

This document is intended to guide the NMDOT and its partners in the statewide functional classification review process following each decennial census.


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Target Audience

While primarily intended to assist persons (in determining functional classification) who are responsible for maintaining the official functional classifications of the state’s public road system, this document is also intended for use by the MPOs, RPOs, and local governments to assist them in proposing functional classification changes for roads within their jurisdiction, following the most recent decennial census.

Document Organization

The remainder of this manual is organized into the following sections:

Section 2.0 – Functional Classification Terminology and Uses

Section 3.0 – Factors Impacting Functional Classification Determination

Section 4.0 – Adjusting Urban Boundaries and Determining Functional Classification

Section 5.0 – Partners in the Functional Classification Process

This document also contains two appendices, including a Glossary of terms and a list of available references for additional information on the functional classification process.

Appendix A: Glossary – Provides terms and definitions commonly used in the functional classification review process.

Appendix B: References – Provides additional resources and references to support the statewide functional classification review process.


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2.0 Functional Classification Terminology and Uses

This section explains the terms used in establishing the functional classification of roadways for the state of New Mexico. Several of these terms are defined in Appendix A - Glossary and will be used throughout this document. It is important to note that FHWA makes a distinction between ‘rural’ states and ‘urban’ states for the purposes of determining functional classification. According to the 2010 Census data, New Mexico is considered an urban state, having more than 75% of its population in urban areas (New Mexico has 75.1% of its population in urban areas). Therefore, the guidance presented here is a combination of general guidance for all states and specific guidance for urban states where noted. The information in this Guide is based on the official FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013 Edition).

2.1 DEFINING FUNCTIONAL CLASSIFICATION For purposes of this Guide, Functional Classification is defined as “the process by which streets and highways are grouped into classes, or systems, according to several factors that contribute to the overall importance of a given roadway to a region or area.” (Highway Performance Monitoring System (HPMS) Field Manual, March 2013). There are seven functional classification categories (or codes) that are used to identify the various functional classes. These are defined in Table 2.1.

Table 2.1 Functional Classification Codes

Classification Description

1 Interstate

2 Principal Arterial - Other Freeways and Expressways

3 Principal Arterial – Other

4 Minor Arterial

5 Major Collector

6 Minor Collector

7 Local


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Based on this classification system, which was reduced from 12 to 7 categories during the HPMS Reassessment (2010), the designation of functional classification is determined separately (and indicated with different codes) from the type or area (Urban or Rural) in which the road resides. As a result, Principal Arterials and Collectors may now exist in both rural and urban areas. These seven classifications, combined with the specification of whether a route is identified as being in a rural or urban area, now provides for 14 possible combinations of functional classification and area type for a state’s road system. For the most part, the top three classifications (Interstate, Principal Arterial-Other Freeways and Expressways, and Principal Arterial-Other), provide similar services in both rural and urban areas. The characteristics of roads in each of the seven functional classifications are briefly described below as noted in the FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013 Edition).

Interstate – Highest class of Arterials; abutting land uses are NOT directly served by them; also have higher speed limits, higher vehicle miles traveled (VMT), and more travel lanes (than Minor Arterials), which results in more mobility (reference Section 3.0); are used for statewide travel, and typically represents the lowest percentage of mileage of the state’s roadway network.

Principal Arterial – Other Freeways and Expressways – Very similar to Interstates, with travel lanes separated by some type of physical barrier, abutting land uses NOT directly served by them; also have higher speed limits, high VMT, and more travel lanes (than Minor Arterials).

Principal Arterial – Other – Serves major centers of Metropolitan Areas and provides a high degree of mobility; abutting land uses may be directly served by them.

These top three functional classifications provide similar service in rural and urban areas. Most high volume roadways in urban areas function as Arterials. One exception is that there may be high volume roads that function as Collectors between Locals and Arterials. These roads provide more mobility, but less accessibility (than Minor Arterials).

Minor Arterial – Used for trips of moderate length, and offer connectivity to the higher Arterial system (Principal Arterials). These roads may carry local bus routes. They offer less mobility (than Principal Arterials), but more accessibility.

Major Collector – Longer in length than Minor Collectors, connects larger traffic generators to the Arterial network; also have lower connecting driveway densities, higher speed limits, higher VMT, more travel lanes, and are spaced at greater intervals (than Minor Collectors); Major Collector mileage is less than Minor Collector mileage.

Minor Collector – Lower speed limits, located in under-served and clustered residential areas; have more connecting driveways, lower VMT than Major


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Collectors, fewer travel lanes, and are spaced at closer intervals than Major Collectors and includes more mileage than Major Collectors.

Local – Account for the highest percentage of all roadways in terms of mileage. Local roads carry no through traffic movement and are used to provide access to adjacent land.

The next section describes some of the federal and state uses for functional classification.

2.2 USES OF FUNCTIONAL CLASSIFICATION At the state and federal level, functional classification is used to evaluate the transportation network’s system performance, benchmarks, and performance targets. Each of the various uses of functional classification are described in the following paragraphs.

Federal Uses of Functional Classification

The federal transportation legislation referred to as Moving Ahead for Progress in the 21st Century (MAP-21) uses functional classification to determine eligibility for funding under the Federal-Aid program. Under this program, “Federal-Aid highway funds are authorized by Congress to assist the States in providing for construction, reconstruction, and improvement of highways and bridges on eligible Federal-Aid highway routes and for other special purpose programs and projects.” (Guide to Federal-Aid Programs and Projects (May 2013), http://www.fhwa.dot.gov/programadmin/publicat.htm.). Federal-Aid highways include “all NHS routes and other roads functionally classified as Interstate, Other Freeways & Expressways, Other Principal Arterials, Minor Arterials, Major Collectors, and Urban Minor Collectors.”(HPMS Field Manual, March 2013). Federal-aid funding is one of the most significant uses of functional classification from the state DOT and local planning partners’ perspective.

Functional classification is also used in the compilation and reporting of the extent, condition and performance of the nation’s highways in the Highway Statistics publication from the FHWA Office of Highway Policy Information. It is also used in preparing the “Status of the Nation’s Highways, Bridges, and Transit: Conditions and Performance (C&P)” report to Congress.

The following table (Table 2.2) provides an example of how functional classification is used in reporting public road mileage (by state). This is a portion of Table HM-20 from the Highway Statistics Series 2011 (http://www.fhwa.dot.gov/policyinformation/statistics/2011/).

Table 2.2 identifies the mileage for each state by functional class and area type (rural or urban). Table 2.3, following Table 2.2 (Table HM-20), illustrates only the values for the state of New Mexico.

http://www.fhwa.dot.gov/programadmin/publicat.htm

http://www.fhwa.dot.gov/policyinformation/statistics/2011/


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Table 2.2 Mileage (by State) by Functional Classification and Area Type


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Table 2.3 Public Road Mileage by Functional Classification and Area Type for New Mexico

Rural Urban

Total Int O F&E

Other PA

Min Art

Maj Coll

Min Coll

Local Tot Int O F&E

Other PA

Min Art

Maj Coll

Min Coll

Local Tot

848 - 1,858 1,950 3,925 3,138 48,762 60,480 152 - 694 640 - 1,493 4,924 7,904 68,384


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State Uses of Functional Classification

State DOTs use functional classification in many decision-making processes for important business areas. These uses are briefly described below (source: FHWA Highway Functional Classification Concepts, Criteria, and Procedures Manual (2013 Edition)).

Program and project prioritization – functional classification is used to prioritize expenditures of projects to maintain the state’s transportation network.

Asset management – functional classification is used to support asset management to protect the state’s most valuable/used assets.

Safety programs – functional classification is used to evaluate and make improvements to a state’s safety programs. For instance, the type of roadway may be considered when evaluating the significance of crash rates on a particular roadway.

Highway design – functional classification impacts the allowable highway design standards such as speed limit, lane width, and horizontal and vertical alignment.

Bridge programs – functional classification is used in a state’s bridge program to make such decisions as where one-lane bridges are acceptable (e.g., on local roads with low traffic volumes).

Traffic control – functional classification may be used to determine the most appropriate intersection control measure to use.

Maintenance – functional classification may also impact scheduling of general roadway maintenance and snow/ice removal in inclement weather.

The next section explains the many factors that impact the determination of functional classification.


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3.0 Factors Impacting Functional Classification Determination

There are many factors that impact the determination of functional classification including mileage, volume, speed, capacity, and existing and future land use development. Each of these factors are described below and each can be closely identified with a particular functional classification.

Mileage – Mileage should be used as a guideline in the primary consideration of determining functional classification. Local roads tend to comprise the majority of statewide road mileage, while Interstates (Principal Arterial) have the least percentage of statewide road mileage.

Volume – Volume is also used to determine functional class as is evidenced by the fact that the higher functional class roads tend to carry higher traffic volumes (relative to the surrounding area). Arterials for instance, tend to carry higher volumes of traffic than other functional classes.

Speed – Arterials tend to have higher speed limits and Locals have lower speed limits.

Route spacing – Arterials are typically spaced at greater intervals than Collectors, which are in turn, spaced at greater intervals than Locals.

Usage – Annual Average Daily Traffic (AADT) and VMT can be used to determine functional classification of a road (as a tie breaker) when trying to determine which of two (or more) similar and roughly parallel roadways should be classified within a higher functional class than the other. In general, the higher the traffic volume, the higher the functional class will be relative to the surrounding area.

Number of travel lanes – Arterials in general have more travel lanes than Collectors and Collectors have more travel lanes than Locals.

Regional and Statewide significance – Arterials carry a majority of traffic through a state, while local roads are not used for statewide travel.


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3.1 FHWA GUIDELINES FOR MILEAGE AND VMT Tables 3.1 (for Arterials) and 3.2 (for Collectors and Locals) are from the FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013 Edition). These tables provide guidelines for mileage and VMT ranges for functional classification of roads. The values identified for Urban States are the values that are used as acceptable ranges in Tables 3.3 and 3.4 for New Mexico.

Tables 3.3 and 3.4 summarize the recommended guidance for determining the functional classification of rural and urban roads in New Mexico. This guidance is revised from New Mexico DOT’s previous guidance document and is supplemented with additional information from the FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013 Edition).


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Table 3.1 VMT and Mileage Guidelines by Functional Classification – Arterials

Source: FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013 Edition)

Notes: 1Ranges in this table are derived from 2011 HPMS data. 2For this table, Rural States are defined as those with a maximum of 75 percent of their population in urban centers.


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Table 3.2 VMT and Mileage Guidelines by Functional Classification – Collectors and Locals

Source: FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013 Edition)

Notes: 1Ranges in this table are derived from 2011 HPMS data. 2Information for Urban Major and Minor Collectors is approximate, based on a small number of States report 3For this table, Rural States are defined as those with a maximum of 75 percent of their population in urban centers.


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Table 3.3 New Mexico Functional Classification Guidance – RURAL Road System

Classification Description/Purpose System Percent

(VMT) System Percent

(mileage) Percent (mileage) in

New Mexico (2011 data)

Interstate Highway Maximum mobility, access only at interchanges

Connects intercity, statewide and interstate long distance trips

18%-34% 1%-2% 1.4%

Principal Arterials

(Rural) –

Other Freeways & Expressways;

Principal Arterials (Rural) - Other

Second highest mobility – minimal interference to through movements

Provides access to important traffic generators and major cities not served by the Interstate, provide access to inter-modal facilities,

High percentage of heavy commercial vehicles

Form an integrated network without stub endings except where unusual geographic conditions exist, are interconnected

Are essential to national security or part of critical transportation infrastructure, serve military facilities

Long distance, high speed trips

Connect population centers of 10,000 or more, (exception is Sunland Park)

PA- Other F&E: 0%-8%

PA-Other:

12%-29%

PA-Other F&E:

0%-2%

PA-Other:

2%-5%

0%

3%

Minor Arterial

Rural

High level of mobility, minimized interference to through movements


Provide inter-county access, Long distance, High speed

Form an integrated network without stub endings except where unusual geographic conditions exist

12%-19% 3%-7% 3%

Major Collector Connect urban areas with populations over 5,000

Serve traffic generators typically of intra-county

12%-24% 10%-17% 6.4%


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Classification Description/Purpose System Percent

(VMT) System Percent



importance (ex. Consolidated schools, employment centers, mines, regional parks), but may also cross county boundaries

Tend to collect traffic from local roads to rural minor arterials

Minor Collector Connect population centers from 500 to 5000

Lower traffic volumes than major collectors

Tend to collect traffic from local roads to rural major collectors and above

3%-10% 5%-13% 5.2%

Local Main function is to provide access to and from residences but may also serve some scattered business and industry

Include most unpaved roads and cul-de-sacs

Tend to have lowest traffic volumes and speeds

7%-20% 66%-74% 80.6%

Note: The percentages shown in Table 3.3 are based on the 2011 HPMS data as indicated in the FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013 Edition). Current VMT is a potential indicator of the importance of the roadway for the county, region, state or nation. However, the amount of traffic carried by a specific roadway is not the main determining factor of functional classification. Traffic volume should be used as a preliminary guideline that is reviewed in conjunction with all of the other roadway and land use characteristics.


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Table 3.4 New Mexico Functional Classification Guidance – URBAN Road System

Classification Description/Purpose System Percent VMT System Percent



Interstate Highway Maximum mobility, access only at interchanges

Connects intercity, state-wide and interstate long distance trips

17%-30% 1%-2% 2%

Principal Arterials

(Urban) –

Other Freeways & Expressways;

Principal Arterials (Urban) - Other

Primary function is to provide the greatest mobility for through movements, direct access to adjacent land is discouraged

Provides access to major traffic generators,

Provide access to inter-modal facilities,

High percentage of heavy commercial vehicles, except where expressly prohibited

Serves most of the trips entering and leaving the urban area


Forms an integrated network without stub connections

Long distance intercity and cross town traffic

High speed trips

Spacing should approximate one mile intervals minimum

PA- Other F&E: 3%-18%

PA-Other:

17%-29%

PA-Other F&E:

0%-2%

PA-Other:

4%-5%

0%

8.7%

Minor Arterial

Urban

Interconnects with and augments the urban principal arterial system

Lower level of travel mobility and a higher rate of access than the principal arterial system


Moderate length distance, moderate speeds

15%-22% 7%-12% 8.1%


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Classification Description/Purpose System Percent VMT System Percent



Forms an integrated network without stub connections

Spacing should be approximately one half to two mile intervals, depending on urban density

Major Collector Provides land access and traffic circulation within residential neighborhoods and commercial and industrial areas.

Serves to distribute trips between the arterial system and the local street network

Provide some degree of mobility and also serve abutting property

7%-13% 7%-13% 0%

Minor Collector Serves both land access and traffic circulation in lower density residential and commercial/industrial areas

Penetrates residential neighborhoods, often only for a short distance

Distributes and channels trips between Local Roads and Arterials, usually over a distance of less than three-quarters of a mile

Operating characteristics include lower speeds and fewer signalized intersections

7%-13% 7%-13% 18.8%

Local Provide direct access to adjacent land

Provide access to higher systems

Carry no through traffic movement

Constitute the mileage not classified as part of the Arterial and Collector systems

6%-24% 67%-76% 62.3%

Note: Table 3.4 was revised in February 2014 for descriptions of Minor Collector and Local roads. The percentages shown in Table 3.4 are based on the 2011 HPMS data as indicated in the FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013 Edition). Current VMT is a potential indicator of the importance of the roadway for the county, region, state or nation. However, the amount of traffic carried by a specific roadway is not the main determining factor of functional classification. Traffic volume should be used as a preliminary guideline that is reviewed in conjunction with all of the other roadway and land use characteristics.


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Mobility and Accessibility

Mobility and Accessibility are also special types of characteristics of a road that are used to determine the primary function of a road for purposes of functional classification. Mobility provides for the throughput of travel on a roadway with limited access using entrance/exit ramps, while accessibility provides for many entrance/exit points along a roadway, which usually results in slower travel mobility capabilities.

Principal Arterials tend to have high traffic volumes and a limited amount of entrance/exit ramps and provide for high mobility. These roads are used frequently by intercity passenger and freight traffic. Local roads (Locals), on the other hand, tend to have many entrance/exit points and provide high accessibility to travelers from neighborhoods to other parts of the transportation network. The classification of roads referred to as Collectors are used to collect traffic from the Locals and connect them to the Arterials. The Collectors typically include a blend of mobility and accessibility characteristics.

One of the biggest challenges in determining functional classification is to distinguish between Major and Minor Collectors. Major Collectors provide more mobility, while Minor Collectors provide more accessibility. In rural areas, AADT and spacing may be the most significant factors in determining the difference between Major and Minor Collector functional classifications.

A Federal Functional Classification Decision Tree (Figure 3.1) may be used to help determine functional class in a priority order based on the functional classification determining factors previously described. Figure 3.1 is also identified as Figure 3-4 in the FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013) Edition.


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Figure 3.1 Federal Functional Classification Decision Tree

Source: Highway Functional Classification Concepts, Criteria, and Procedures (2013 Edition)

Figure 3.1 indicates that the first decision to be made is whether or not a road functions as an Arterial; this decision is followed by determining if a road functions as a Collector; Roads are finally classified as Local roads if they do not meet the criteria for Arterials or Collectors.

The next section discusses an important process that precedes functional classification determination and that is the adjustment of Urban Boundaries based on Census-defined boundaries. The section also provides guidance on how to determine the appropriate functional classification for a particular route or segments along a route.


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4.0 Adjusting Urban Boundaries and Determining Functional Classification

Since the process for determining functional classification begins after official approval is received from FHWA regarding any adjusted urbanized area boundary changes (based on the most recent decennial census), this section begins with a discussion of urban boundaries and how/why they are adjusted after each decennial census. For purposes of the following discussion, “Adjusted Urban Area Boundaries” refers to the FHWA boundary adjustment process in all areas of population of 5,000 and above.

4.1 URBAN BOUNDARIES Prior to reviewing and revising the functional classification of roads in a state, the census-defined urban boundaries must be reviewed, revised or ‘adjusted’ as needed, and approved by FHWA. Based on census-defined boundaries (population, density, etc.) some of the reasons for adjusting the urban boundaries may include consistency of functional classification of similar-function roads, or for geographic continuity. Based on this evaluation, roads used by urban residents, but outside of urban boundaries may be classified as an urban road.

“There are differences in the way FHWA and the Census Bureau define and describe urban and rural areas. The Census Bureau defines urban areas solely for the purpose of tabulating and presenting Census Bureau statistical data….According to 23 U.S.C. 101(a) (33), areas of population greater than 5,000 can qualify as urban, in contrast to the Census Bureau’s threshold of 2,500. There are also differences in the terminology used to describe sub-categories of urban areas. FHWA refers to the smallest urban area as a Small Urban Area, while the Census Bureau refers to Urban Clusters”. (Highway Functional Classification Concepts, Criteria and Procedures, 2013 Edition). NOTE: For the purpose of the boundary adjustment process, the term “adjusted urban area boundaries” refers to the FHWA boundary adjustment process in all areas of population 5,000 and above. Table 4.1 illustrates the FHWA Urban Area Types defined by population range.


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Table 4.1 FHWA Urban Area Types Defined by Population Range

FHWA Area Definition Population Range

Allowed Urban Area Boundary Adjustments

Urban Area 5,000+ Yes

Small Urban Area (from Clusters)

5,000 – 49,999 Yes

Urbanized Area 50,000 + Yes

“Federal transportation legislation allows for the outward adjustment of Census Bureau defined urban boundaries (of population 5,000 and above) as the basis for development of adjusted urban area boundaries for transportation planning purposes, through the cooperative efforts of State and local officials.” (Highway Functional Classification Concepts, Criteria and Procedures, 2013 Edition)

The only official requirement regarding adjusting urban boundaries is that any adjustment must expand not contract the Census Bureau urban boundary; that is, any adjustments to urban boundaries must include the entire existing Census defined urban area (of population 5,000 and above) within the new urban boundary. The expectation is that local planning partners will review the U.S. Census urban area boundaries in the context of the existing adjusted urban area boundaries (based upon the previous census) and determine the extent to which the boundaries should be adjusted for transportation planning purposes. Local planning partners should submit their proposed adjustments to their state DOTs. The state DOT then reviews proposals and ensures that no territory considered urban by the Census Bureau is left out of the adjusted urban area boundary. Once the adjusted urban area boundaries are submitted to FHWA and approved, a statewide review of functional classification is conducted by the state DOT to determine where functional classifications changes need to be made in the corresponding road network databases. The following are the same databases used to support the annual HPMS report.

GIS Tools for Analysis and Revision of Urban Boundaries

There are many automated tools available to state DOTs and local planning agencies, from a variety of vendors, that allow the user to view and analyze data in a geospatial environment (displayed on a map), including functional classification data and urban area boundaries. The most widely used tools are those associated with a Geographic Information System (GIS). GIS is a collection of software and hardware that allows for the integration of different types of data (referred to as data layers), to be displayed on a map. The underlying databases that support GIS systems are referred to as geospatial databases. The data in the databases are stored in tables where all types of data are available. In the case of a state DOT, the types of data include roadway feature data and functional classification of routes. In a GIS system, the road network data with


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functional classification can be color-coded with different colors and line weights to indicate different functional classifications. The road network can then be compared with other data layers, as needed, including geographic boundaries for urban areas or hydrographic features such as lakes, or other transportation centers such as airports.

Generally, state DOTs maintain some type of GIS system (or multiple systems) that contains their state’s road network. Roadway features, characteristics, and events are typically linked to the road network using a linear referencing system (LRS), and there is typically a specific GIS-based application used for federal reporting purposes. A state DOT may have multiple GIS systems that support specific business areas such as planning, construction, traffic operations, or they may have an enterprise GIS system that integrates data from several business areas for use throughout the organization.

One of the most important data layers in the GIS is the LRS for the road network. The road LRS is typically defined with some type of route identification information (e.g., route name, number) and includes begin and ending termini data, which may be milepoints, intersections, etc. A GIS system and associated tools provides a unique way for state DOTs to view their functional classification data for their road network compared to other geographic data layers that may include hydrography layers or in the case of functional classification, urban area boundaries. By overlaying the urban boundaries over the road network, it is easy to identify roads that are ‘within’ or ‘outside’ of the urban areas.

The latest guidelines from FHWA indicate that roads should be functionally classified based on their primary use or function and that the classification should not automatically change at the entrance to/exit from urban boundaries. Roads near those boundaries should be closely reviewed to ensure that the functional classification accurately portrays the function (or use) of the road.

Figure 4.1 illustrates the MPO and RPO boundaries in the state of New Mexico. The process of reviewing and revising urban boundaries begins with analyzing the urban boundaries identified by the most recent Census, based on population. The boundaries are then adjusted based on a set of guidelines, procedures and tools that includes the participation of state DOT and local planning agencies (MPOs, RPOs, local governments) in recommending where boundaries should be adjusted. The planners also have to ensure that any existing urban boundaries are included in the revised or expanded urban boundary.

To facilitate recommendations for functional classification changes and the review of urban boundaries, a web-based map-share tool was developed for NMDOT as part of the Statewide Functional Classification Review Project (2013). This tool allows the user to draw a boundary around a roadway section or other geographic area displayed on a map at any location within New Mexico. The user can then add comments (similar to a note pad feature) to the map which then allows others to view the map via web access and to add additional


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comments or make recommendations. An online user’s guide is also provided with the Map Viewer tool.


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Figure 4.1 New Mexico MPO/RPO Boundaries


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4.2 PROCEDURAL STEPS FOR DETERMINING

FUNCTIONAL CLASSIFICATION There is a series of basic procedural steps recommended in the FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013 Edition) for determining functional classification. The steps are illustrated in Figure 4.2 and are described below. These steps should be used for roads whether within a rural or urban area.

Step 1: Identify traffic generators (e.g., shopping centers, airports, truck terminals, schools, casinos, parks and recreational areas, etc.)

Step 2: Rank traffic generators – separate into urban and rural groupings

Step 3: Map traffic generators – use graduated symbols of varying sizes to illustrate smallest to largest traffic generators

Step 4: Determine the appropriate functional classification to connect traffic generators. Start with these classifications in this order:

1. Arterials

a. Interstates

b. Other Freeways & Expressways

c. Other Principal Arterials

d. Minor Arterials

2. Collectors

a. Major Collectors

b. Minor Collectors

3. Locals

Step 5: Use the following criteria to classify Arterials:

a. Does the road have full or partial access control?

b. Preserve the continuity of Arterials from/to and through rural and urban areas

c. Arterials should avoid neighborhoods

d. Most high-volume roads in urban areas function as Arterials. Exception to this rule is that there may be high volume roads that function as Collectors between Local roads and Arterials.

e. Minor Arterials usually intersect roadways in ALL other functional classifications, while Principal Arterials should only terminate at other Arterials.


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Figure 4.2 Determining Functional Classification

1. Identify Traffic Generators

2. Rank Traffic Generators

3. Map Traffic Generators 4. Determine functional classification to connect

traffic generators

5. Use Criteria to Classify

Arterials

7. Use Criteria to classify

Collectors

9. Designate/identify Local Roads

6. Use Criteria to classify Principal Arterials in

Urban Areas

8a. Determine Major Collector

8b. Determine Minor Collector

10. Compare FC changes with recommended

Mileage and VMT by FC

11. Submit Functional Classification Change

Request form


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Step 6: Use the following criteria for Principal Arterials (PAs) in urban areas:

a. Principal Arterials provide more mobility

b. Minor Arterials provide more accessibility

c. PAs serve:

i. air, rail, bus, and truck terminals

ii. regional shopping centers

iii. large colleges, medical complexes, military bases

iv. major industrial and commerce centers

v. important recreational areas

d. Spacing between PAs should be greater than between Minor Arterials

Step 7: Use the following criteria to classify Collectors:

a. Roads that provide an important land access function

b. Roads that serve to funnel traffic between Local roads and Arterials

c. Roads that provide access to residential neighborhoods

Step 8: Use the following criteria to distinguish between Major and Minor Collectors:

a. Major – connects larger traffic generators to the Arterial network; roadway is busier, with more signal-controlled intersections

b. Minor – provides access to under-served residential areas and clustered residential areas. In rural areas, Minor Collectors have approximately equal distance between Arterial and Major Collector routes for equal population density.

Step 9: Designate/identify Local roads. These are the remaining roads not otherwise classified as Arterials or Collectors.

Step 10: Compare functional classification changes with recommended mileage and VMT by FC. State DOTs should continue (as a routine process) the evaluation of how closely the mileage and VMT percentage guidelines (Tables 3.3 and 3.4 for New Mexico) are followed in determining the functional classifications for the state’s road network.

Step 11: Submit a Functional Classification Change Request Form (MPOs and RPOs submit the form to NMDOT and NMDOT submits the form to FHWA). Figure 4.3 illustrates the Functional Classification Change Request Form for New Mexico.


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Figure 4.3 New Mexico Functional Classification Change Request Form

Functional Classification Change Request Form State of New Mexico

Sponsored by

Contact Name:

Email: Phone:

Date

Street Name

Current Functional Classification (e.g., Interstate, Minor Collector, Minor Arterial, etc.):

Proposed Functional Classification:

Route Description (entire route)

Termini of segment(s) proposed for reclassification (acceptable termini include intersections, interchanges, and in rare cases adjusted urbanized area boundaries):

Estimated length of segments proposed for reclassification: (to the nearest thousandth of a mile)

Connecting Routes (with equal or higher functional class; include Route name, Route number, intersection location with connecting route):

Reason for requested change:

Land Use Along Route:

Characteristics of Traffic Served:

Ownership and Maintenance (responsible entity)

Ownership: Maintenance:

Traffic count & Traffic Year Traffic Count: Traffic Year:

Note: Original of this document (with authorized signatures) should be sent to the NMDOT Transportation Planning and Safety Division and forwarded to FHWA. A copy of this document shall be retained at the offices of the sponsoring entity (i.e., MPOs, RPOs, NMDOT District Office).


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General Rules

The following set of General Rules apply to the functional classification process for all states:

There is no need to change a road’s functional classification specifically at urban/rural boundaries. Instead, changes should occur based on an actual change in the roadway’s function. Therefore, particular attention should be paid to roadways close to boundaries.

Roadway that connect to Principal Arterials are probably other Principal Arterials, Minor Arterials, or Collectors.

A higher functionally classified road can “split” its traffic between two lower-level roads with different levels of accessibility and mobility.

Avoid assigning same functional classification to parallel routes. Select the predominant route (perhaps based on VMT) to assign the higher order route classification.

A single connection between two traffic generators is all that is required.

Ensure that each route terminates at a route of the same or higher functional classification. There may be some exceptions to this rule. For example, an Interstate Spur that terminates in an urbanized area may become a Principal Arterial.

In general, the more intense the land development, the closer the spacing of roadways within the same functional classification.

Future routes should be functionally classified with the existing system if they are in the Statewide Transportation Improvement Program (STIP) and are expected to be under construction within the STIP timeframe of 4 years or less.

Use same functional class for existing and future routes until future route is constructed. Future routes are not part of public mileage certification (for HPMS) until ‘open to traffic’.

Functional Class (FC) coding for ramps should be the same as the highest FC of mainline roadways served by the ramp (HPMS Field Manual, March 2013).

States and their local partners should have a documented methodology and follow it as consistently as possible. This guidance document for New Mexico serves as the documented methodology for determining functional classification in the state.

Table 4.2 presents recommended milestones and timeframes for submittal of the Functional Classification network. These are the milestones used for the New Mexico Statewide Functional Classification Review Project (2013), which resulted in this Guidance Manual. As a reminder, any recommended functional


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classification changes for roads on the NHS need to be coordinated with the FHWA Headquarters Office of Planning, Environment, and Realty.

Table 4.2 Key Milestones for Development and Submittal of the Functional Classification Network

Event Month Following FHWA Adjusted Urban Boundary

Approval

State DOT launches the formal functional classification update process after FHWA approves the State’s adjusted urban area boundaries

Month 1

State DOT works with planning partners to review and propose changes to the functional classification of its roadways

Months 2-17

State DOT gathers and processes all proposed functional classification changes and submits draft final data and/or maps to FHWA division office for review

Months 18-20

State DOT incorporates updates into planning process and related databases to ensure submittal of updated functional classification in upcoming June 15th HPMS Submittal

Months 22-24

(source: FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013 Edition))


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5.0 Partners in the Functional Classification Process

The NMDOT Planning Division should utilize the existing partnerships with MPO and RPO planners to support the functional classification process. MPOs are the primary local contact for the DOTs in urbanized areas for the purposes of determining functional classification of roads in those areas. MPOs may initiate functional classification revisions requests on their own or on behalf of their member jurisdictions.

State DOT regional or district offices may be responsible for submitting system revisions for all state highways outside an MPO’s planning area and for coordinating proposed changes for areas within the planning jurisdiction of an MPO. Counties can also recommend changes for roads under their jurisdiction and outside MPO planning areas. Local governments can also submit requested changes to the state DOT.

A Public Review process is necessary to ensure that there is participation from local governments and the public in recommending any functional classification changes. It is important for the state DOT to solicit this public participation, since functional classification changes have a potential impact on funding for road projects at the local level. This process typically includes the MPOs and RPOs and/or local governments. To support this need in New Mexico, a Public Review Plan was also developed as part of the New Mexico DOT Statewide Functional Classification Review Project (2013). A copy of that plan is available

from the NMDOT Transportation Planning and Safety Division. The web-based map-share tool developed for New Mexico (as described in Section 4.0) can be used to facilitate the participation of local partners in the public review process.

5.1 RESPONSIBILITY FOR MAINTAINING FUNCTIONAL

CLASSIFICATION In an effort to maintain the most up to date functional classification of a state’s road network, state transportation agencies must:

1) Review urban area boundary maps as provided by U.S. Census after each decennial Census and adjust as needed.

2) Assign functional classification of roads as needed for new roads or re-classify existing roads based on how the road functions. That is, functional classification should be assigned based on actual functional criteria, rather than the location of the roadway within an urban or rural area.


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The following set of questions may be used to determine the primary function of the road, with the understanding that all roads provide some form of mobility and accessibility to some degree (FHWA Highway Functional Concepts, Criteria and Procedures Manual, 2013 Edition).

Have there been any improvements or modifications to existing roads and corridors in the state?

Have new significant roadways been constructed that may warrant Arterial or Collector status?

Has any previously non-divided Principal Arterial roadway been reconstructed as a divided facility?

Has any new major development (such as an airport, regional shopping center, major medical facility) been built in a location that has caused traffic patterns to change?

Has there been significant overall growth that may have caused some roadways to serve more access or mobility needs than they have previously?

Have any Arterial or Collector roadways been extended or realigned in such a way to attract more through trip movements?

Has a particular roadway experienced a significant growth in daily traffic volumes?

According to the FHWA Updated Guidance for the Functional Classification of Highways Memorandum, October 14, 2008, “the practice of automatically upgrading the functional classification of a rural route that crosses an urban boundary should be phased out and eliminated. Upgrading the functional classification due to an actual change in function should be the operative criteria, rather than the location of the urban/rural boundary.”

NMDOT Functional Classification Guidance Manual Appendix

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A. Glossary

Accessibility: Accessibility is the term used to describe the amount of entrance and exit points are located on a particular roadway. Roads with few entrance/exit points are described as having controlled access or limited access. Roads with more entrance/exit points provide greater accessibility.

Arterial: Functional classification used to describe roads in a state that provide high mobility, are used for throughput of travel, and have limited or controlled access.

Collector: Functional classification used to describe roads that collect traffic from the Locals and connect them to the Arterials. The Collectors typically include a blend of mobility and accessibility characteristics.

Federal Aid Program: A program “authorized by Congress to assist the States in providing for construction, reconstruction, and improvement of highways and bridges on eligible Federal-Aid highway routes and for other special purpose programs and projects.” (Guide to Federal-Aid Programs and Projects (May 2013),

Functional Classification: A hierarchy used to classify roads in a state according to their function with respect to and in consideration of adjacent land use.

HPMS: Highway Performance Monitoring System. The HPMS national database is used to evaluate and report the extent, performance and condition of the nation’s transportation system to Congress in the Status of the Nation’s Highways, Bridges, and Transit: Conditions and Performance (C&P) report

Local: Functional classification used to describe roads that carry no through traffic movement and are used to provide access to adjacent land.

Mobility: Mobility is the term used to describe the throughput of travel on a particular roadway.

National Highway System: The National Highway System (NHS) is a network of nationally significant highways approved by Congress in the National Highway System Designation Act of 1995. It includes the Interstate System and over 117,000 miles of other roads and connectors to major intermodal terminals.

Rural Area: All other areas of the state not included in the boundaries of an urban area.

STIP: Statewide Transportation Improvement Program is a document that includes a state’s project and funding priorities for a 3-to-5 year period. The STIP is generated by the state DOT Planning Division and involves Federal and State government, Metropolitan Planning Organizations, or MPOs, transit agencies, LPAs, and the public. These groups help determine the project and funding priorities for a 3-to-5 year period that are incorporated into something called the


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Statewide Transportation Improvement Program, or STIP. Urban Area: “The Census Bureau identifies two types of urban areas: ‘urbanized areas’ of 50,000 or more people and ‘urban clusters’ of at least 2,500 and less than 50000 people.”

(http://www.census.gov/newsroom/releases/archives/2010_census/cb12-50.html).

Examples of Urbanized Area in New Mexico include the following (based on the 2010 Census data): Albuquerque, Farmington, Las Cruces, Los Lunas, and Santa Fe.

Examples of Urban Clusters in New Mexico include the following (based on the 2010 Census data): Alamogordo, Artesia, Aztec, Carlsbad, Roswell, Silver City, and Taos.


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B. References

FHWA Highway Functional Classification Concepts, Criteria and Procedures Manual (2013 Edition) FHWA Updated Guidance for the Functional Classification of Highways Memorandum, October 14, 2008 HPMS Field Manual, March 2013 AASHTO’s A Policy on Geometric Design of Highways and Streets (a.k.a. Green Book) FHWA’s Flexibility in Highway Design Manual New Mexico DOT Public Review Plan (2013)

Documents

NMDOT Functional Classification Guidance Manualwhich are the allowable design standards (i.e. speed, horizontal and vertical alignment, etc.). While reviewing the existing functional