Graphics header for Chapter 4 A Framewoek for Walkable Urban Thoroughfare Design with images of sidewalks, pedestrians and schematics behind the text

Purpose

This chapter describes a set of tools for use by practitioners planning and designing walkable urban thoroughfares. It describes a design framework to identify and classify context and thoroughfares and describes how the controls of context and thoroughfare type are used in the design process to establish design parameters.

The functional classification system classifies context as either rural or urban. In this report, the definition and description of the conventional urban context is expanded to provide more detailed descriptions of adjacent surroundings and to provide a way to use context as a criterion in the selection of thoroughfare type and design criteria. Context zones are used to classify urban contexts into discrete types, ranging from lower to higher density and intensity of development.

The approach described in this chapter introduces thoroughfare types as a complement to functional classification to provide a broader range of thoroughfare design choices. The use of thoroughfare types restores the former practice of distinguishing streets by their design characteristics in addition to their functional classification.

Objectives

This chapter:

1. Defines context as used in urban thoroughfare design and explains the features of urban areas that create and shape context;

2. Introduces the concept of "context zones" and provides guidance to help practitioners use this tool;

3. Describes the features that create context including land use, site design and urban form, and building design;

4. Describes the different types of thoroughfares and their relationship to functional classifications; and

5. Describes features of thoroughfare types and context zones that result in compatibility.

Introduction

The design of viable, well-functioning urban thoroughfares depends on a clear understanding of the application of CSS principles in designing thoroughfares in the urban environment. Once urban context is understood, the function of each thoroughfare can be established and the design parameters can be selected to achieve a balance between land use and transportation design. This linkage demands special tools. While it is possible to "feel" the character of an urban area, it can be hard to define and describe the specific features that collectively give shape and character to a particular urban setting, whether it is a small town, activity center, main street, or high-density regional downtown.

Not only does context influence the design of thoroughfares, but the design of the thoroughfare itself helps to define and shape the context as much as adjacent land uses and buildings define and shape context. For these reasons, this document recommends a clear focus on context first, followed by detailed transportation planning to support the context in a balanced way.

Conventional thoroughfare design processes emphasize vehicular mobility and the provision of automobile access to adjoining land uses, primarily using functional classification, traffic volume and design speed as the determinants for design parameters. The principles of CSS expand the design process to better integrate thoroughfares with their surroundings. The result in many communities is a new emphasis on urban thoroughfares with features that emphasize multimodal safety and mobility as well as support for the activities of the adjacent land uses. Walkability, a key focus of this document, is better planned with an initial, clear focus on context.

A main tenet of walkable thoroughfare design is encapsulated in the phrase "one size does not fit all," which means the function of a thoroughfare and its design should complement the context that it serves, and the design of the thoroughfare should change as the existing and planned context changes. This tenet challenges the conventional design process used by many state and municipal agencies, which applies a single roadway cross-section, based on functional classification, to a thoroughfare—regardless of the context. In this report, it is context and the change in context that determines the need to transition from one thoroughfare type to another and also determines the corresponding change in design parameters.

Thoroughfare planning and engineering requires evaluating capacity, connectivity and safety considerations in combination with meeting local objectives for urban character. The selection of appropriate design controls and performance measures, discussed further in Chapter 7, is a key step in developing suitable design solutions. The design scenarios presented in Chapter 6 provide illustrations of how context sensitive objectives can be evaluated under alternative designs and integrated into a preferred alternative.

Features that Create Context

Often, transportation planning and design considers context only in terms of land use (traffic generation) and two elements of site design—parking and access (driveways). The CSS design process for walk-able urban thoroughfares expands this understanding of context to include the aspects of building and site design that create support for pedestrian and transit activity and that relate to the design of thoroughfares to result in integrated walkable environments.

Land Use

Land use is a common criterion for characterizing urban development and estimating vehicle trip generation, particularly in single-use, vehicle-dominated locations. The design framework in this report identifies land use as an important contributor to context and a major factor in the selection of design criteria (particularly as these relate to levels of pedestrian activity), assembly of the cross-section components and allocation of the width of the right of way.

In addition to having a fundamental impact on automobile travel demand, variations in adjacent land use affect the width and design of the streetside, the part of the thoroughfare between the curb and edge of right of way including sidewalks. As detailed in Chapter 8, residential uses typically have less need for sidewalk space than similarly scaled mixed-use blocks with ground floor commercial retail uses, where space for window shopping, outdoor dining, newspaper racks and other street appurtenances add to the sidewalk width. Areas that disperse land uses into single-use areas and that rely on hierarchical circulation networks generally result in longer trips, less walking and bicycling and more dependence on motor vehicles. Commercial uses generate higher volumes of pedestrian travel and business activities that use the street-side compared to similarly scaled residential uses. With respect to the traveled way, the part of the thoroughfare between curbs, variations between residential and commercial areas include parking- and travel-lane width. Commercial areas typically have a higher volume of large vehicles such as delivery trucks and buses and have a higher turnover of on-street parking than residential areas. Thus, a predominantly commercial thoroughfare often requires a wider traveled way when compared to a predominantly residential thoroughfare in the same context zone. Commercial areas usually generate more traffic than residential areas, which affects decisions related to the number of lanes, access control and intersection design.

Site Design and Urban Form

The ways in which buildings, circulation, parking and landscape are arranged on a site has an effect on where a thoroughfare and its context fall in the continuum of walkability (see sidebar on the Continuum of Walkability in Chapter 1). The specific elements of site design that contribute to defining urban context include:

Building Design

The design of buildings is a significant contributor to context and the priority that the context gives to walking. Building height, density and floor-area ratio, architectural elements, mass and scale, relationship to adjacent buildings and thoroughfares, orientation of the entry, and the design and type of ground floor land uses can help shape context and create an environment that is more or less walkable.

Development in contexts that give a lower priority to walking generally are more internally oriented as evidenced by how the buildings sit on their sites (as discussed above) and how the ground floor uses lack supportive relationships with adjacent streetsides and sidewalks. The lack of walkability in these contexts is not correlated with building intensity but with features of building and site design.

Buildings in locations with a traditional urban character that contributes to a walkable community are typically oriented toward the street. Ground floor uses in urban buildings are usually oriented to the pedestrian passing on the adjacent sidewalk (for example, retail, restaurant, services) and incorporate architectural elements that are interesting, attractive and scaled to the pedestrian (Figure 4.1).

Photo image from street level of a tree-lined sidewalk with shops and storefronts. No pedestrians or cars are visible.

Figure 4.1 Pedestrian-scaled architectural elements. Source: Community, Design + Architecture.

Some aspects of how building design helps define urban context include:

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Figure 4.2 Illustration of height to width ratios that create a scale on thoroughfares that is comfortable to people and encourages walking (human scale). Human scale ratios fall between 1:3 and 1:2 as measured from the building fronts. Source: Community, Design + Architecture.

(Extended text description: Graphic illustrations in three sections. The top section shows a line of illustrated cars, buses, trees and people, with dotted horizontal, vertical and diagonal lines to show the difference in heights and ratios. The lower section has two similar images on the left and right. The side of the drawing is building elevation with a 1:2 ratio. There are people, a tree, a car and a bus in line going out from the building elevations. There is a diagonal dotted line moving from the lower left corner of each drawing toward the upper right corner of each drawing. The two dotted lines are perpendicular.)

 

More information on how building design promotes context sensitivity and sustainability can be found in Promoting Sustainable Transportation through Site Design, an ITE recommended practice and in the Smart-Code (see References for Further Reading at the end of this chapter). All elements of building design provide strong cues for the selection of a thoroughfare design.

Context Zones

Context zones describe the physical form and character of a place. This includes the mass or intensity of development within a neighborhood or along a thoroughfare. Context zones are applied at the community unit level, but for the purposes of thoroughfare design must be interpreted on a block-by-block basis to respond to specific physical and activity characteristics. Figure 4.4 contains the descriptions of the six context zones. Zones C-3 through C-6 are urban zones that relate to urban thoroughfare design.

Photo image from street level of a road, tree-line sidewalk, and storefronts. There is a parent and child talking the middle of the image. There are more pedestrians at the end of the shown street. There are posts along the edge of the sidewalk.

Figure 4.3 The frequency of articulation of a building facade contributes to a scale that is comfortable to pedestrians. Source: Community, Design + Architecture.

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Figure 4.4 Illustration of a gradient of development patterns ranging from rural in Context Zone 1 (C-1), to the most urban in C-6. Source: Duany Plater-Zyberk and Company.

(Extended text description: Graphic illustration showing the range from Rural to Transect to Urban, moving horizontally across the graphic. As the illustration moves from Rural on the left side to Transect in the center to Urban on the right side, the illustration is divided by black vertical lines, creating various sections. The first section has graphic representation of trees, bushes, fields and is designated as C-1 Natural Zone. The second section has trees, crop fields, bushes and a roadway, and is designated as C-2 Rural Zone. These first two sections are part of the Rural Context Zones. The third section has trees, homes,and roadways and is designated as C-3 Suburban Zone. The fourth section has some trees, with homes, buildings and several roads and is designated as C-4 General Urban Zone. The fifth section has few trees, many buildings and more major roadways, and is designated as C-5 Urban Center Zone. The sixth section has large buildings, smaller building, major tree-lined roadways and is designated as C-6 Urban Core Zone. These four sections are part of the Urban Context Zones. The last section on the far right side has large buildings, what seems to be parking lots, tree-lined roadways and is designated as DA Assigned District. This is under the Districts subheading. There are two additional dotted lines which are perpendicular.)

 

Selecting a Context Zone in Thoroughfare Design

The design process presented in this report uses context zones as a primary consideration in selecting the design parameters of urban thoroughfares. This is a refinement to the "rural" and "urban" classifications that are critical in selecting design criteria in A Policy on the Geometric Design of Highways and Streets (AAS-HTO 2004). Context zones are an important determinant of basic design criteria in traditional urban thoroughfares. This chapter helps the practitioner identify and select context zones as one of the first steps in the design process.

As Table 4.1 shows, context is defined by multiple parameters, including land use, density and design features. Table 4.1 presents the full range of context zones, but this report focuses on urban contexts (C-3 through C-6). The "distinguishing characteristics" column in the table, for example, describes the overall relationship between buildings and landscape that contributes to context. In addition to the distinguishing characteristics and general character, four attributes assist the practitioner in identifying a context zone: (1) building placement—how buildings are oriented and set back in relation to the thoroughfare; (2) frontage type—what part of the site or building fronts onto the thoroughfare; (3) typical building height; and (4) type of public open space.

Guidelines for identifying and selecting a context zone include the following:

1. Consider both the existing conditions and the plans for the future, recognizing that thoroughfares often last longer than adjacent buildings.

2. Assess area plans and review general, comprehensive and specific plans, zoning codes and community goals and objectives. These often provide detailed guidance on the vision for the area.

3. Compare the area's predominant land use patterns, building types and land uses to the characteristics presented in Table 4.1.

4. Pay particular attention to residential densities and building type, commercial floor-area ratios and building heights.

5. Consider dividing the area into two or more context zones if an area or corridor has a diversity of characteristics that could fall under multiple context zones.

6. Identify current levels of pedestrian and transit activity or estimate future levels based on the type, mix and proximity of land uses. This is a strong indicator of urban context.

7. Consider the area's existing and future characteristics beyond the thoroughfare design, possibly extending consideration to include entire neighborhoods or districts.

Thoroughfare Types

The design process in this report refers to both functional classification and thoroughfare type to classify streets.

The purpose of each classification as used in CSS applications for areas with traditional urban characteristics is described below. • Functional classification—defines a thoroughfare's function and role in the network, in addition to governing the selection of certain design controls. The practitioner may use functional class to determine:

These factors are used to inform the practitioner's decisions related to both the physical design and operations of the thoroughfare.

Table 4.1 Context Zone Characteristics

Context Zone Distinguishing Characteristics General Character Building Placement Frontage Types Typical Building Height Type of Public Open Space Transit (Where Provided)
C-1 Natural
Natural landscape
Natural features
Not applicable
Not applicable
Not applicable
Natural open space
None
C-2 Rural
Agricultural with scattered development
Agricultural activity and natural features
Large setbacks
Not applicable
Not applicable
Agricultural and natural
Rural
C-3
Suburban
Primarily single family residential with walkable development pattern and pedestrian facilities, dominant landscape character. Includes scattered commercial uses that support the residential uses, and connected in walkable fashion. Detached buildings with landscaped yards, normally adjacent to C-4 zone. Commercial uses may consist of neighborhood or community shopping centers, service or office uses with side or rear parking. Varying front and side yard setbacks Residential uses include lawns, porches, fences and naturalistic tree planting. Commercial uses front onto thoroughfare. 1 to 2 story with some 3 story Parks, green-belts Local, express bus
C-4
General Urban
Mix of housing types including attached units, with a range of commercial and civic activity at the neighborhood and community scale Predominantly detached buildings, balance between landscape and buildings, presence of pedestrians Shallow to medium front and side yard setback Porches, fences 2 to 3 story with some variation and few taller workplace buildings Parks, green-belts Local, limited stop bus rapid transit, express bus; fixed guideway
C-5 Urban Center Attached housing types such as townhouses and apartments mixed with retail, workplace and civic activities at the community or sub-regional scale. Predominantly attached buildings, landscaping within the public right of way, substantial pedestrian activity Small or no setbacks, buildings oriented to street with placement and character defining a street wall Stoops, dooryards, storefronts and arcaded walkways 3 to 5 story with some variation Parks, plazas and squares, boulevard median landscaping Local bus; limited stop rapid transit or bus rapid transit; fixed-guideway transit
C-6 Urban Core Highest-intensity areas in sub-region or region, with high-density residential and workplace uses, entertainment, civic and cultural uses Attached buildings forming sense of enclosure and continuous street wall landscaping within the public right of way, highest pedestrian and transit activity Small or no setbacks, building oriented to street, placed at front property line Stoops, dooryards, forecourts, storefronts and arcaded walkways 4+ story with a few shorter buildings Parks, plazas and squares, boulevard median landscaping Local bus; limited stop rapid transit or bus rapid transit; fixed-guideway transit
Districts
To be designated and described locally, districts are areas that are single-use or multi-use with low-density development pattern and vehicle mobility priority thoroughfares. These may be large facilities such as airports, business parks and industrial areas.
As applicable

(Based on transect zone descriptions in SmartCode Version 9.2, 2008. Source: Duany Plater-Zyberk & Company.) Cells with italics text represent Context Zones that are not addressed in this report.

Graphic illustration from above street level of a tree-lined boulevard, divided roadway. Shops and buildings line each side, with sidewalks. Cars are parked on the sides of the roads in each direction. There are cross walks at the intersections, with pedestrians.

Figure 4.5 Illustration of a boulevard. Source: Claire Vlach, Bottomley Design & Planning.

Additionally, use thoroughfare type to determine the following design controls:

Table 4.2 shows specific thoroughfare types that are commonly used in the United States and gives a general description of each type. As this report focuses on urban thoroughfares in walkable areas, only three of the types in Table 4.2 fall into this category: boulevards, avenues and streets. These thoroughfare types typically serve a mix of modes, including pedestrian, bicycle users, private motor vehicles (for passenger and freight) and transit.

Boulevards are typically larger thoroughfares with medians (Figure 4.5). They serve a mix of regional and local traffic and carry the most important transit routes. The multiway boulevard is a variant of a boulevard that contains separated roadways for through and local access traffic. Multiway boulevards may be considered when balancing the needs of abutting land uses (for example, curb parking, pedestrian facilities, land access, fronting buildings) with arterial functions. See Chapter 6 for more discussion of multiway boulevards.

Avenues (Figure 4.6) and streets (Figure 4.7) are similar to each other in form but avenues can be up to four lanes with a median. Streets are generally two lanes and serve predominantly local traffic. In walk-able areas, all thoroughfare types have a strong pedestrian orientation.

Table 4.3 shows the relationship between thoroughfare types and functional classification. In general, boulevards serve an arterial function, avenues may be arterials or collectors and streets typically serve a collector or local function in the network.

Figure 4.6 Illustration of an avenue. In this example on-street parking is dropped to gain width for a left turn lane at the intersection. Source: Claire Vlach, Bottomley Design & Planning.

Graphic illustration of tree-lined boulevard, traffic in both directions. Shops, buildings and sidewalks line the roadway. Cars drive along the lanes, and cars are parked on the roadside. Pedestrians pass in the crosswalk in the intersection.

Figure 4.7 Illustration of a street. Source: Claire Vlach, Bottomley Design & Planning.

Table 4.2 Thoroughfare Type Descriptions

Thoroughfare Type Functional Definition
Freeway/Expressway/ Parkway
Freeways are high-speed (50 mph +), controlled-access thoroughfares with grade-separated interchanges and no pedestrian access. Includes tollways, expressways and parkways that are high- or medium-speed (45 mph +), limited-access thoroughfares with some at-grade intersections. On parkways, landscaping is generally located on each side and has a landscaped median. Truck access on parkways may be limited.
Rural Highway
High-speed (45 mph +) thoroughfare designed both to carry traffic and to provide access to abutting property in rural areas. Intersections are generally at grade.
Boulevard
(see Chapters 8, 9 and 10 for design guidance)
Walkable, low-speed (35 mph or less) divided arterial thoroughfare in urban environments designed to carry both through and local traffic, pedestrians and bicyclists. Boulevards may be long corridors, typically four lanes but sometimes wider, serve longer trips and provide pedestrian access to land. Boulevards may be high-ridership transit corridors. Boulevards are primary goods movement and emergency response routes and use vehicular and pedestrian access management techniques. Curb parking is encouraged on boulevards.
Multiway boulevards are a variation of the boulevard characterized by a central roadway for through traffic and parallel access lanes accessing abutting property, parking and pedestrian and bicycle facilities. Parallel access lanes are separated from the through lanes by curbed islands with landscaping; these islands may provide transit stops and pedestrian facilities. Multiway boulevards often require significant right of way.
Avenue
(see Chapters 8, 9 and 10 for design guidance)
Walkable, low-to-medium speed (25 to 35 mph) urban arterial or collector thoroughfare, generally shorter in length than boulevards, serving access to abutting land. Avenues serve as primary pedestrian and bicycle routes and may serve local transit routes. Avenues do not exceed 4 lanes, and access to land is a primary function. Goods movement is typically limited to local routes and deliveries. Some avenues feature a raised landscaped median. Avenues may serve commercial or mixed-use sectors and usually provide curb parking.
Street
(see Chapters 8, 9 and 10 for design guidance)
Walkable, low speed (25 mph) thoroughfare in urban areas primarily serving abutting property. A street is designed to (1) connect residential neighborhoods with each other, (2) connect neighborhoods with commercial and other districts and (3) connect local streets to arterials. Streets may serve as the main street of commercial or mixed-use sectors and emphasize curb parking. Goods movement is restricted to local deliveries only.
Rural Road
Low speed (25 to 35 mph) thoroughfare in rural areas primarily serving abutting property.
Alley/Rear Lane
Very low-speed (5 to 10 mph) vehicular driveway located to the rear of properties, providing access to parking, service areas and rear uses such as secondary units, as well as an easement for utilities.

Cells with italics text represent thoroughfare types that are not addressed in this report.

 

Table 4.3 Relationship Between Functional Classification and Thoroughfare Type

Please see extended text description below

Shaded cells represent thoroughfare types that are not addressed in this report.

(Extended text description: Graphic chart for Thoroughfare Types. In the lefthand column is Functional Classicification: Principal Arterial, Minor Arterial, Collector, Local. Across the top is Freeway/Expressway/Parkway, Rural Highway, Boulevard, Avenue, Street, Rural Road, Alley/Rear Lane. There are thick black horizontal bars to show where certain types are grouped with each other. For Principal Arterial, the black bar extends from Freeway/Expressway/Parkway, Rural Highway, Boulevard, Avenue, to Street. For Minor Arterial, the black bar extends from Rural Highway, Boulevard, Avenue, to Street. For Collector, the black bar extends from Avenue, Street, to Rural Road. For Local, the black bar extends from Street, Rural Road, to Alley/Rear Lane. The Freeway/Expressway/Parkway, Rural Highway, Rural Road and Alley/Rear Lane columns are shaded. These shaded areas represent thoroughfare types that are not addressed in this report.)

 

More detailed descriptions of the general design parameters and desired operating characteristics of the thoroughfare types are given in Table 4.4. As mentioned above, this document focuses on the three types that can be considered urban thoroughfares: boulevards, avenues and streets. Those thoroughfare types serving areas with traditional urban characteristics are suitable for the four urban context zones C-3, C-4, C-5 and C-6.

Chapter 5 provides an overview of the design process and identifies how the selection of context zones and thoroughfare types relates to each stage of thoroughfare design. Chapter 6 presents design parameters and criteria for each thoroughfare type based on a combination of functional class, context zone and whether the surrounding land use is predominantly commercial or residential.

Works Cited

American Association of State Highway and Transportation Officials. 2004. A Policy on the Geometric Design of Highways and Streets, 5th edition. Washington, DC: AASHTO.

Duany, Andres. 2000. "A Theory of Urbanism." Scientific American (December).

Duany, Andres. 2002. Journal of Urban Design, Special Edition Dedicated to the Transect.

Institute of Transportation Engineers. 2010. Promoting Sustainable Transportation Through Site Design: An ITE Recommended Practice. Washington, DC: ITE.

Sources of Additional Information

Bosselman, MacDonald and Kronemeyer. Environmental Quality of Multiple Roadway Boulevards— Monograph 53. Berkeley, CA: Institute of Urban and Regional Development, University of California at Berkeley. April 1997.

Duany, Andres and, Sandy Sorlien and William Wright. SmartCode—A Comprehensive Form-Based Planning Ordinance, Version 9.2. 2008.

Jacobs, Allen B. Great Streets. MIT Press. 2001.

Jacobs, Allen B., Elizabeth MacDonald and Yodan Rofe. The Boulevard Book: History, Evolution, Design of Multiway Boulevards. MIT Press. 2003.

Table 4.4 Urban Thoroughfare Characteristics

Urban Thoroughfare Type Number of Through Lanes Desired Operating Speed
(mph)
Transit Service Emphasis Median Driveway Access Curb Parking Pedestrian Facilities [1] Bicycle Facilities Freight Mvmt. [2]
Freeway
4 to 6+
45-65
Express
Required
No
No
No
Optional separated pathway or shoulder
Regional truck route
Expressway/ Parkway
4 to 6
45-55
Express
Required
No
No
Optional separated pathway
Optional separated pathway or shoulder
Regional truck route
Boulevard 4 to 6 30-35 Express and Local Required Limited Optional Sidewalk Bike lanes or parallel route Regional truck route
Multiway Boulevard 4 to 6 25-35 Express and Local Required on access lanes Yes from access lane Yes on access roadway Sidewalk Regional route/ local deliveries only on access roadway
Avenue 2 to 4 25-30 Local Optional Yes Yes Sidewalk Bike lanes or shared Local truck route
Street 2 25 Local or none No Yes Yes Sidewalk Shared Local deliveries only
Rural Road
2
25-35
Local or none
No
Yes
No
No
Shared or shoulder
Local deliveries only
Local Street
2
25
Local or none
No
Yes
Yes
Sidewalk
Shared
Local deliveries only
Alley/Rear Lane
1
5-10
None
No
Yes
No
Shared
Shared
Local deliveries only

Cells with italics text represent thoroughfare types that are not addressed in this report.

Notes: [1] Boulevard, Multiway Boulevard, Avenue, and Street thoroughfare types have sidewalks on both sides. Sidewalk width varies as a function of context zone, fronting land use and other factors. [2] Freight movement is divided into three categories: 1) Regional truck route, 2) Local truck route and 3) Local deliveries only. Cells show highest order of truck movement allowed.