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Highway Functional Classification: Concepts, Criteria and Procedures ii TABLE OF CONTENTS Section 1. Introduction .. 1 1.1 Overview 2 Section 2. Concepts 4 2.1 Introduction . 4 2.2 Functional Classification Concepts 4 2.2.1 Access versus Mobility . 4 2.3 Other Important Factors Related to Functional Classification 7 2.4 System Continuity .. 11 Sectio n 3. Criteria 14 3.1 Definitions and Characteristics . 14 3.1.1 Interstates . 14 3.1.2 Other Freeways & Expressways .. 14 3.1.3 Other Principal Arterials .. 15 3.1.4 Minor Arterials 15 3.1.5 Major and Minor Collectors .. 16 3.1.6 Local Roads 17 3.2 Putting it all Together . 18 3.3 A Real World Example 19 3.4 Final Considerations .. 21 Section 4. Procedures .. 25 4.1 Introduction .. 25 4.2 Identifying the Functional Classification of a Roadway Network .. 25 4.2.1 Arterial Considerations 27 4.2.2 Collector Considerations . 28 4.2.3 Genera l Rules of Thumb for All Categories and the System as a Whole .. 28 4.3 Good Practices .. 29 4.3.1 Ongoing Maintenance of the Functional Classification System 29 4.4 Geographic Information Systems . 32 4.4.1 Proactive Communication and Accessibility of Information .. 33 4.5 Partners in the Functional Classification Process . 33 4.5.1 Metropolitan Planning Organizations 33 4.5.2 State DOTs 34 4.5.3 Counties and Other Agencies .. 34 4.6 Suggested Procedural Tasks 34 Section 5. Applications .. 40 5.1 Performance ..40 5.2 Data Needs and Reporting 40 5.2.1 Impact of Functional Classification Changes .40 5.3 Secondary Functional Classification Uses ..40 5.4 Highway Design .. 41
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Highway Functional Classification: Concepts, Criteria and Procedures iii 5.4.1 The Relationship between Functional Classification and Design . 41 5.4.1.1 AASHTO Green Book and Flexibility in Highway Design 42 5.4.1.2 Livability . 42 5.4.1.3 Smart Transportation Guidebook .. 43 5.4.1.4 CSS in Designing Major Urban Thoroughfares for Walkable Communities . 44 5.5 Assessment of Function al Classification Systems . 45 5.6 Emerging/Other Functional Classification Systems 45 5.7 Future Trends 48 Section 6. Urban Boundaries . 49 6.1 Introduction . 49 6.2 Defining Urban and Rural . 50 6.2.1 Census Definitions .. 50 6.2.2 FHWA Definitions 501 6.3 Relationship to Functional Classification 52 6.4 Developing Adjusted Urban Area Boundaries . 53 6.4.1 Adjusted Urban Area Boundaries ΠTechnical Tasks 53 6.4.2 Consideration Factors for Adjusting Urban Areas .. 54 6.5 Adjusted Urban Area Boundaries ΠProcedural Tasks 58 6.5.1 Risk Factors to Urban Area Adjustment Schedule . 58 6.5.2 Urban Area Adjustment Schedule . 59 6.6 Adjusted Urban Area Boundaries ΠData Transmittal Requirements .. 62 Section 7. Graphics Sources .63
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Highway Functional Classification: Concepts, Criteria and Procedures iv LIST OF TABLES Table 2 -1: Relationship between Functional Classification and Travel Characteristics .. 11 Table 3 -1: Characteristics of Urban and Rural Arterials . 15 Table 3 -2: Characteristics of Urban and Rural Minor Arterials 16 Table 3 -3: Characteristics of Majo r and Minor Collectors (Urban and Rural) 17 Table 3 -4: Characteristics of Urban and Rural Local Roads 18 Table 3 -5: VMT and Mileage Guidelines by Functional Classifications – Arterials .. 22 Table 3 -6: VMT and Mileage Guidelines by Functional Classifications Œ Collectors and Locals .. 23 Table 4 -1: Example Massaschusetts Roadway Functional Classification Table ..38 Table 4 -2: Key Milestones for Development and Submittal of the Functional Classification Network .. 39 Table 5 -1: Oregon DOT™s Classification System . 45 Table 6 -1: US Census Bureau Urban Area Types Defined by Population Range 51 Table 6 -2: FHWA Urban Area Types Def ined by Population Range . 51 Table 6 -3: Key Milestones for Development and Submittal of Adjusted Urban Area Boundaries 62 Table 6 -4: Geospatial Database Required Attributes . 62 LIST OF FIGURES Figure 1 -1: Principal Arterial – Other Freeways & Expressways .. 2 Figure 1 -2: HOV Lane on Interstate 95 in Woodbridge, VA . 3 Figure 1 -3: Other Principal Arterial in California . 3 Figure 2 -1: Aerial View of the Eisenhower (and Johnson) Tunnels along I -70, west of Denver, CO . 5 Figure 2 -2: View from Inside the Eisenhower Tunnel .. 5 Figure 2 -3: Aerial View of Eisenhower Court, North Platte, NE . 5 Figure 2 -4: Aerial View of Eisenhower Street in Carrolton, TX 6 Figure 2 -5: Illustration of Access -Mobility Dynamic 6 Figure 2 -6: Collector Example .. 7 Figure 2 -7: Example of Access Points .. 7 Figure 2 -8: Functional Classification Map of Giddings, TX and Surrounding Unincorporated Territory . 10 Figure 2 -9: Schematic Illustrating the Concept of Continuity .. 12 Figure 2 -10: Example of an Exception to the Connectivity Guidelines, Wings Neck Road, Bourne, MA . 12 Figure 2 -11: Example of an Interstate Spur Terminating at a City Street in Holyoke, MA .. 13 Figure 3 -1: Example of Interstate .. 14 Figure 3 -2: Example of Other Principal Arterial 15 Figure 3 -3: Example of Urban Minor Arterial . 15
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Highway Functional Classification: Concepts, Criteria and Procedures v Figure 3 -4: Federal Functional Classification Decisi on Tree .. 18 Figure 3 -5: Map of an Urban Area™s Roadway Network . 19 Figure 3 -6: Map of a Rural Area™s Roadway Network .. 19 Figure 3 -7: Worcester, MA Roadway System .. 20 Figure 3 -8: Classification Overlap 21 Figure 4 -1: Minnesota DOT Functional Classification Change Request Form 31 Figure 4 -2: Example of Shifting due to Inconsistency between Tabular Event Data and Geospatial Data . 32 Figure 4 -3 Sample Roadway Color Scheme 33 Figure 4 -4: Good -Practice Timeframe for Functional Classification Updates in Months . 35 Figure 5 -1: fiTable 5.1 Roadway Categoriesfl from the Smart Transportation Guidebook, March 2008 43 Figure 5 -2: Community Arterial Roadway Design Guidelines in Smart Transportation Guidebook . 44 Figure 5 -3: Idaho DOT™s Proposed Redefinition of Functional Street Classifications .. 47 Figure 5 -4: ITE Report: Context Sensitive Solutions in Designing Major U rban Thoroughfares for Walkable Communities . 47 Figure 6 -1: Prototypical Urban and Rural Areas 50 Figure 6 -2: Example of Roadway Coinciding with Adjusted Urban Area .. 53 Figure 6 -3: 2000 Census Urban Cluster and Urbanized Areas (Ohio and Vicinity) 54 Figure 6 -4: Example Original Urban Area .. 55 Figure 6 -5: Example Single Contiguous Area 55 Figure 6 -6: Example Area Expanded to Cover Air Force Base . 56 Figure 6 -7: Example Area Expanded to Include Industrial Area 56 Figure 6 -8: Example Boundary Adjusted to Align with Major Roadway 57 Figure 6 -9: Example Boundary Adjusted for Simplicity 57 Figure 6 -10: Good Practice Level of Procedural Steps for an Urban Boundary Update Process .. 59
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Highway Functional Classification: Concepts, Criteria and Procedures 2 In conducting functional classification updates, State departments of transportation ( DOTs ) strive for consensus with potentially dozens of agencies, including metropolitan and rural planning agencies, loc al officials and FHWA Division Offices . Geospatial technologies and travel demand forecasting capabilities have advanced significantly, greatly lowering the cost of data storage and increasing analysis capabilities . Planners and engineers have expanded roa dway design options significantly, especially in areas where providing for non -motorized travel is a priority . Transportation agencies have developed their own classification terms to describe these options . 1.1 Overview This guidance document builds upon and updates the two most recent guidance documents circulated by FHWA, namely: Highway Functional Classification : Concepts, Criteria and Procedures, March 1989 Updated Guidance for the Functional Classification of Highways Memorandum, October 14, 2008 1 1. All functional classification categories will now exist in both urban and rural areas . Specifically, all Principal Arterial sub -categories and all Collector sub -categories will be recognized in both urban and rural forms . The following revised functional classification categories should be used: a. Principal Arterial i. Interstate ii. Other Freeways & Expressways (OF&E) (Figure 1 -1) iii. Other (OPA) b. Minor Arterial c. Collector i. Major Collector ii. Minor Collector d. Local 2. States should assign functional classification s according to how the roadway is functioning in the current year only . With regar d to future routes , roads should be functionally classified with 1 http://www.fhwa.dot.gov/policy/ohpi/hpms/fchguidance.cfm Figure 1-1: Principal Arterial – Other Freeways & Expressways Source: Ohio Statewide Imagery Program
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Highway Functional Classification: Concepts, Criteria and Procedures 3 the existing system if they are included in an approved Statewide Transportation Improvement Program (STIP) and are expected to be under construction within the STIP timeframe of 4 years or less . Use the current classification for roadways, even replacement roadways that will upgrade the roadway, until construction is complete . Reclassify the new roadway once it has been constructed. 3. Ramps and other non -mainline roadways are to be assigned the same functional classification as the highest functional classification among the connecting mainline roadways served by the ramp. (Figure 1 -2) 4. Principal Arterial roadways (Figure 1 -3) serve a large percentage of travel between cities and other activit y centers, especially when minimizing travel time and distance is important . For this reason, Arterials typically are roadways with high traffic volumes and are frequently the route of choice for intercity bus es and trucks . The spacing of Arterials in urban areas is closely related to the trip -end density characteristics of activity centers in urban areas. The spacing of these facilities (in large r urban areas) may vary from less than 1 mile in highly developed central business areas to 5 miles or more in the sparsely developed urban fringes. Figure 1-3: Other Principal Arterial in Californi a Sourc e: Akos Szoboszlay Principal Arterials play a unique role in providing a high degree of mobility and carry ing a high proportion of travel for long distance trips . These facilities carry the major portion of trips entering and leaving an activity center , as well as the majority of throu gh movements that either go directly through or bypass the area . Roadways that fall into the Principal Arterials – Other Freeways & Expressways category are limited -access roadways that serve travel in a similar way to the Interstates. Transportation agencies apply a variety of treatments to preserve mobility and increase the person throughput of Urban Arterials, including ramp metering, high -occupancy -vehicle (HOV) lanes and high – occupancy toll lanes . Figure 1-2: HOV Lane on Interstate 95 in Woodbridge, VA Source: www.roadstothefuture.com
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4 SECTION 2. CONCEPTS 2.1 Introduction This section of the guidance document presents the concepts underlying the functional classification of roadways. It first introduces the two primary transportation functions of roadways, namely mobil ity and access, and describes where different categories of roadways fall within a continuum of mobility -access . In addition to mobility and access, other factors that can help determine the proper category to which a particular roadway belongs Š such as trip length, speed limit, volume, and vehicle mix Š are discussed in this section. While Arterials, Collectors and Local s span the full range of roadway functions, the Federal functional classification scheme uses additional classification categories to describe these functions more precisely . Distinctions between access -controlled and full -access roadways ; the urban a nd rural development pattern ; and subtleties between fimajorfl and fiminorfl sub -classifications are key considerations when determining t he Federal functional classification category to which a particular roadway belongs . The process of determining the correc t functional classification of a particular roadway is as much art as it is science . Therefore, a real -world example is presented to help make the discussion of functional classification more readily understood. 2.2 Functional Classification Concepts Most travel occurs through a network of interdependent roadways, with each roadway segment moving traffic through the system towards destinations . The concept of functional classification defin es the role that a particular roadway segment plays in serving this flow of traffic through the network . Roadways are assigned to one of several possible functional classification s within a hierarchy according to the character of travel service each roadway provides . Planners and engineers use this hierarchy of roadways to properly channel transportation movements through a highway network efficiently and cost effectively . 2.2.1 Access versus Mobility Road ways serve two primary travel needs: access to/egress from specific locations and travel mobility . While t hese two functions lie at opposite ends of the continuum of roadway function, most roads provide some combination of each . Roadway mobility function: Provides few opportunities for entry and exit and therefore low travel friction from vehicle access/egress Roadway accessibility function: Provides many opportunities for entry and exit , which creates potentially higher friction from vehicle access/egress The fl ow of traffic throughout a roadway network is similar to the flow of blood through the human circulatory system or the trunk and branch system of a tree . The units moving through the system (blood cells, nutrients, vehicles, etc.) move through progressivel y smaller network elements as they approach their destination.
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Highway Functional Classification: Concepts, Criteria and Procedures 5 These two roles can be best understood by examining two extreme examples (Figure 2 -1 and Figure 2 -2). First, consider the Eisenho wer Tunnel west of Denver, CO. Located along Interstate 70, the Eisenhower Tunnel runs under the Continental Divide in the Rocky Mountains and is one of the longest tunnels in the United States . Motorists that travel through the tunnel are en route to a di stant location and are using the roadway completely to serve their fimobilityfl needs . There is no location that is immediately fiaccessiblefl to the roadway . Next, consider the example of Eisenhower Court in North Platte, NE (Figure 2-3). This roadway is travelled almost exclusively by the individuals that live along the roadway . Hence, the roadway entirely provide s fiaccessibilityfl and offers almost nothing in terms of mobility. Figure 2 -4 depicts the neighborhood around Eisenhower Street in Carro llton, TX. This roadway serves both mobility needs (the residents that live along the side streets that intersect Eisenhower Street use it for some level of north/south mobility) and land access needs (there are both residential and commercial properties located alo ng the roadway). Figure 2-3: Aerial View of Eisenhower Court, North Platte, NE Source: G oogle Earth Pro, June 27, 2012 Figure 2-1: Aerial View of the Eisenhower (and Johnson) Tunnels along I -70, west of Denver, CO Source: G oogle Earth Pro, June 27, 2012 Figure 2-2: View from Inside the Eisenhower Tunnel Source: Creative Commons Attribution -Share Alike 2.0 generic license; Benjamin Clark
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