Graphics header for Chapter 3 Network and Corridor Planning with images of sidewalks, pedestrians and schematics behind the text

Purpose

This chapter describes the interrelationship between the broader transportation network, corridors and individual thoroughfare segments. It presents how the principles of CSS can be used in the planning for urban thoroughfares at the network, region, or corridor levels to support or create walkable places. Understanding this relationship will contribute to the consideration of key issues and community objectives and to the development of a broader set of alternatives and improved flexibility when planning and developing transportation improvement projects.

This chapter provides the network plan context from which transportation projects are selected for further development and design. The chapter is intended to provide background related to network planning, but other documents; such as the upcoming ITE Planning Urban Roadway Systems and the CNU Statement of Principles on Transportation Networks contain recommendations on how to prepare such plans.

This report emphasizes the introduction of CSS principles early in the planning process. Network and corridor planning is an early opportunity to integrate community goals into specific urban thoroughfare projects. This helps expedite the project development process by identifying and addressing key issues and community objectives early, rather than for the first time during the planning and design of an individual thoroughfare project. Integrating CSS principles into the network and corridor planning process can:

The early integration of CSS principles will influence desired change systematically rather than a piecemeal process.

 

The Roles of Network and Corridor Plans

Long Range or Regional Network Plan:

Corridor Plan:

Project Development Process:

 

Objectives

This chapter

1. Provides CSS principles and considerations for planning and designing transportation networks and corridors;

2. Provides guidelines on how CSS principles can be applied and design issues addressed at the network or corridor planning level;

3. Emphasizes that solutions may be found at the scale of the network and corridor rather than the individual thoroughfare (such as a denser network of streets or parallel facilities that provide equivalent function and capacity to the alternative of widening an individual thoroughfare); and

4. Shows how thoroughfares function within a network and how the CSS approach to improvements of specific segments of a thoroughfare relate to the thoroughfare's role in the network.

The guidelines presented in this chapter apply to both new development and retrofit conditions. Improving an existing situation will depend on the degree of connectivity, flexibility and capacity of the existing network, and the extent the network can be modified to accommodate the desired improvements.

Introduction

Chapter 2 presented a broad overview of the transportation planning and project development processes and described how CSS principles can be applied in each step of the process. This chapter builds on Chapter 2 by describing principles and guidelines that can be used at the network and corridor scales to create or improve urban walkable areas.

Network, or "system," planning sets the strategic direction and framework around which the various components and facilities will eventually be constructed or redeveloped. It is a series of high-level incremental plans leading to the design of individual thoroughfare segments that is consistent with the framework. Network planning defines goals for all modes of transportation and facilities. These long-range plans typically contain:

The long-range transportation plan should consider the role and function of a multimodal transportation network for an entire region or metropolitan area. Corridors are transportation pathways that provide for the movement of people and goods between and within activity centers. A corridor plan encompasses single or multiple transportation routes or facilities (such as thoroughfares, public transit, railroads, highways, bikeways, trails, or sidewalks), the adjacent land uses and the connecting network of streets.

Corridor planning encompasses a scale that is large enough to consider the context and network, but small enough to be comprehensible by the public. Corridor planning applies multiple strategies to achieve specific land use and transportation objectives along a transportation corridor, combining capital improvements and management strategies into a unified plan for the corridor.1

(Note 1: Corridor planning as defined by the New York State Department of Transportation.)

 

CSS in Network Planning

Oftentimes the challenges encountered creating more walkable urban thoroughfares can be resolved at the scale of the network or the corridor. Network planning:

Familiar characteristics addressed include:

Ideally, network planning takes place at the early stages of regional development and is integrated into a comprehensive planning process that concurrently addresses land use, transportation and environmental resource management. In practice, especially in areas with multiple jurisdictions, network planning is often conducted in a piecemeal manner by multiple agencies with different geographic jurisdictions, missions and powers. For the practitioner planning or designing a thoroughfare segment, considering network design and function can lead to solutions that balance between demands for vehicle throughput and support for adjacent development.

The design process—the subject of this report—needs to recognize the role of a thoroughfare as part of a large-scale, multimodal network. The project development process should consider the regional, subregional and neighborhood functions of the thoroughfare in relation to urban form and character. The design of the individual thoroughfare, therefore, is linked to both its context and the performance of the network. A multi-modal network may identify some thoroughfares that emphasize vehicles or trucks, while others emphasize pedestrians and transit.

CSS merges a community's comprehensive corridor objectives with mobility objectives in a manner acceptable to a variety of stakeholders. Two critical common characteristics for desirable thoroughfares are compatibility and support for the corridor context and providing a high degree of multimodal connectivity.

The context may vary along the length of the thoroughfare. The combination of function, context, or other changes may cause the design of the thoroughfare to vary along its length.

Network characteristics have a meaningful impact on urban development patterns. For example, compact, mixed-use areas are dependent on a pattern of highly connected local and major thoroughfares. The high level of connectivity results in short blocks that provide many choices of routes to destinations, support a fine-grained urban lot pattern and provide direct access to many properties. Walkable suburban areas should be similarly supported by a high level of street or path connectivity.

One fundamental tension that is commonly encountered in the application of CSS principles is between the desire of local residents to emphasize character and walkability in thoroughfare design and the desire of transportation agencies to emphasize vehicle capacity or the ability to accommodate projected regional travel demand. The tension between these objectives is best addressed through consideration of the broader network and corridor in conjunction with the individual thoroughfare.

Network characteristics are factors that provide opportunity for CSS. Connectivity, parallel routes and corridor capacity contribute to a transportation system that can accommodate projected demand by dispersing traffic, transit, freight and bicyclists across a system of parallel roadways.

This report addresses urban thoroughfares except limited-access facilities and local streets. However, when considering network design, properly located express thoroughfares—freeways/tollways, expressways and parkways—supplement the urban arterial thoroughfare network by providing high-speed, high-capacity service for longer trips. High vehicular capacity facilities permit other thoroughfares to balance the movement of traffic with other local objectives. If well connected to the larger thoroughfare network, local streets can also provide parallel capacity in the network to accommodate local, shorter trips.

Photo image from overhead of a suburban neighborhood. A major roadway is running vertically through the image, with curving residential roadways branching off on either side. About 90% of the roadways are lined with residences, but a few are alongside natural open spaces like parks or other green spaces.

Figure 3.1 Example of a conventional network. Source: Data available from U.S. Geological Survey, EROS Data Center, Sioux Falls, SD.

Effective Network Planning for Walkable Areas

Network planning at the regional scale by regional or metropolitan planning agencies typically includes only highways, arterials and major collector systems. The planning of the finer grid of local residential and commercial streets is typically prepared at the county and/or city scale. As described above, regional network planning establishes the framework for the planning of county- and citywide networks. County- and citywide transportation plans establish a framework for planning and designing the local street system and individual thoroughfares. Finally, site planning and the project development process achieve the highest level of detail. The network types discussed below encompass both regional and local scales, since later discussions on thoroughfare design are influenced by the pattern of fine-grain networks.

Network Types

Most urban areas have a system of arterial streets, some of which may be highways. The most efficient systems have arterials with extended continuity, usually traversing all or much of an urban area except where barriers exist. The most efficient urban net-works—which provide enough parallel streets to provide route flexibility and an opportunity for special street functions—have arterials spaced at half a mile or less. The important features of the arterial systems are connectivity and continuity.

Photo image from overhead of an urban neighborhood. Major roadways run diagonally from the lower left corner radiating up toward the upper right corner. The major roadways are intersected with perpendicular smaller roadways. Buildings line about 95% the roadways,, with a  few sections appearing to be parks or other open green spaces.

Figure 3.2 Example of a traditional network.

Source: Data available from U.S. Geological Survey, EROS Data Center, Sioux Falls, SD.

Within the arterial street framework is a finer network of thoroughfares. These finer networks are sometimes characterized as either "traditional" or "conventional."

The typical conventional street network is often characterized by a framework of widely spaced arterial roads with connectivity limited by a system of large blocks, curving streets and a branching hierarchical pattern often terminating in cul-de-sacs (Figure 3.1). In contrast, traditional networks (Figure 3.2) are typically characterized by a less hierarchical pattern of short blocks and straight streets with a high density of intersections.

The prototypical traditional and conventional networks differ in three easily measurable respects: (1) block size, (2) degree of connectivity and route choice and (3) degree of curvature. While the last measure does not significantly affect network performance, differences in block size and connectivity create very different characteristics.

Comparative Advantages

Both network design types have advantages. Advantages of traditional grids include

In contrast, conventional networks have some advantages over traditional urban grids. Advantages of conventional networks include:

Both traditional grid and conventional networks have livability impacts that may be considered a benefit or detriment, depending on the context and one's perspective. The impact of traditional grids results from the dispersion of traffic, resulting in some local residential streets experiencing higher traffic volumes than a similar street in a conventional network. The impact of conventional networks is the concentration of traffic, congestion and associated impacts into fewer residential arterials and collectors.

Urban Form and Transportation Networks

Transportation and land use interact with each other. Such relationships can vary by land use type, whether on a regional, community, or localized scale. This section describes this relationship.

Metropolitan planning organizations (MPOs) model travel behavior using area types such as central business district, fringe and rural. The U.S. Census Bureau definitions aid in planning by defining urban areas and dividing them into urbanized areas having more than 50,000 population and urban clusters having less than 50,000 population. Rural areas make up the remainder of the land area. Urbanized areas have structured MPO planning procedures and guide the allocation of federal transportation funding. Comprehensive plans for communities also identify areas as commercial, residential, or office use.

None of these definitions sufficiently describes urban context at a level of detail that relates the context to the transportation system or to thoroughfare design. Designers need to know the intensity of urban development and the desired travel modes that best serve its users. Context intensity gradations—called context zones—distinguish the urban built environment adjacent to and surrounding thoroughfares.

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 typically applied at the neighborhood or community level, but for the purposes of thoroughfare design, context zones are interpreted on a block-by-block basis to respond to specific physical and activity characteristics. Chapter 4 further describes context zones and describes how they are used in designing walkable urban thoroughfares. In planning, understanding the context zones sets the scale for design of the regional transportation network as well as individual transportation facilities.

Planning Urban Transportation Networks

Urban thoroughfare design should be based on a combination of local needs and the role of the thoroughfare in the area or region's transportation network. The thoroughfare network should be planned to support the needs generated by the planned land uses (including intensity) while at the same time being compatible with the characteristics of the resulting neighborhoods and community—areas that may have widely varying needs, features and activity levels. The community may also have a variety of goals associated with specific neighborhoods, areas, or corridors that the thoroughfares (individual and as a network) should support.

The thoroughfare network develops from its existing state and expands in accordance with a community's comprehensive plan (or transportation plan). The density (spacing) of the network, the capacity (lanes, walkway, bicycle, transit), the space for furnishings and other components of the right of way should encourage and support the development pattern, land use type and level of development intensity in accordance with the plan. The total transportation network should function as a system of thoroughfares consisting of vehicular, pedestrian, bicycle and transit facilities that together meet and support the needs of the communities' desired urban form and growth.

Figure 3.3 shows a simplified example of a network of thoroughfares, along with context zones. For illustrative purposes, the network contains a principal street that passes through several different context zones, typical of many major thoroughfares. Also shown are boulevards, avenues and streets in a highly connected network that ultimately connects to the regional highway system. Network capacity, in the form of a dense system of thoroughfares (not necessarily more travel lanes on individual facilities), needs to be greatest in the high-intensity areas.

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Figure 3.3 Context based development patterns are formed around a highly connected network of walkable thoroughfares. Source: Thomas Low (DPZ) and Digital Media Productions.

(Extended text description: Graphic illustration showing Conventional Development Patterns on the left side with an arrow pointing downward and Context Based Developmental Patterns on the left side with an arrow pointing upward. In the center to right, there is a graphic illustration showing different network connections. The upper area shows a more rural region with one straight major roadway through the center and more winding roads between wooded/tree areas. The center section of the illustration transitions to a more urban/suburban area, with regular roadways with right angle intersections. Some sections in this area are bisected with more frequent roadways, creating a tighter grid pattern. The far right side of illustration has more rural/tree areas with curving roadways. The bottom section has a more free-flowing suburban area, with some right-angled intersections and straight-roads and other more curving, smaller roads. There is a key at the bottom of the illustration: A dark box for Urban Core, a medium gray box for Urban Center, a darker box for General Urban, a light gray box for Suburban. A medium gray line for Main Street, a darker double line for Boulevard, a medium dark line for Avenue, a medium dark double line for Street.)

 

The level of capacity in these high-intensity areas will depend on the degree of interaction among local land uses, the amount of multimodal activity generated and the amount of through travel using the network. As further described in Chapter 4, the design of the individual thoroughfare needs to respond, adjust and support the different development and activities associated with changes in context zone.

Network Planning Principles for Walkable Urban Thoroughfares

The following principles describe an approach for planning and designing urban thoroughfare networks that are sensitive to community objectives and context and will help create a more walkable environment on appropriate facilities in the network. These principles should be considered together to create effective networks.

Planning Multimodal Networks

Indices For Network Connectivity and Accessibility

Sources: Texas Transportation Institute, Adapted from: Donohue, Nick, "Secondary Street Acceptance Requirements," Office of the Secretary of Transportation, Commonwealth of Virginia. Spring 2008. "Smart Growth Index Model," U.S. EPA 2002.

Network planning should be refined and updated to define alignments and to establish the role of thoroughfares as more detailed planning and development occur.

Street Connectivity and Spacing

Please see extended text description below

Figure 3.4 The collector in a typical hierarchical network (A) channels traffic from local streets to the arterial street system. A system of parallel connectors (B) provides multiple and direct routes between origins and destinations. Source: Kimley-Horn and Associates, Inc. and Digital Media Productions.

(Extended text description: A graphic illustration with two sections. The upper section is titled (A) Conventional Suburban Hierarchial Network with a large major suburban roadway curving around and away from a shopping center area in the lower right corner. Dotted lines radiate and intersect in straight lines from the curving roadway, creating property plots. There is a larger dotted line moving through the main roadway from the shopping center along the outside of the shown neighborhood into the center of the illustrated neighborhood. The lower section of the illustration is titled (B) Traditional Urban Connected Network with larger major urban roadways in a regular grid-like pattern moving up and down and side to side. Smaller dotted lines radiate away and intersect with the roadway (creating property plots). There is a shopping center in the lower right corner. There is a larger dotted line moving through the larger major roadway from the shopping center and through the roadways in the center of the lower illustration.)

 

Performance Measures

Performance measures should be selected to describe how well the system will perform in accordance with network objectives. Such measures are often used to compare network plan alternatives or measure performance of a network according to specific objectives. The following may aid in selecting appropriate measures: • Select transportation performance measures that reflect stakeholder objectives and priorities for the system or facility being planned or designed. Some of these may not be strictly transportation measures but include economic development and other types of measures.

NCHRP Report 446, A Guide to Performance-Based Transportation Planning, provides more information on performance measurement.

Network Design Guidelines

This section provides specific considerations and guidelines for network design. The guidelines provided in this section are applicable for:

1. Greenfield development—establishing, augmenting, or reconfiguring a system of thoroughfares to serve an undeveloped or newly developing area or long-range plans for future development.

2. Reuse and redevelopment—large projects in mature urban areas that permit reconfiguration or changes in the function of adjacent or nearby thoroughfares. In these situations, changes might include the following:

Ten Thoroughfare Network Planning Principles

Major thoroughfare networks should

1. Connect and provide access to and between communities, centers of activity and neighborhoods of all types, as well as recreational and cultural facilities;

2. Form a gridlike pattern of continuous thoroughfares except as precluded by topographic barriers;

3. Conform with and follow natural topographic features and avoid adverse impacts to natural resource areas;

4. Meet spacing and connectivity criteria similar to those presented in this chapter;

5. Be designed to efficiently accommodate emergency vehicles, providing multiple routes to reach any block;

6. Have thoroughfares interconnected with specified distances between intersections to provide choices of routes to reduce travel distances; to promote use of transit, bicycles and walking; and to efficiently accommodate utility needs;

7. Provide signalized crossings to encourage use of walking, bicycles and transit;

8. Be comprehensible to the average traveler;

9. Communicate the intended functions of individual thoroughfares through both design characteristics and appearance; and

10. Develop operating plans to serve all modes and all users, with uses varying on some thoroughfares according to context, needs, objectives and priorities while considering overall network needs.

3. Facility reconstruction—reconstruction of major sections of one or more thoroughfares provides an opportunity to make network changes more compatible with existing context/land uses, such as converting from a two-way thoroughfare to a one-way couplet (or vice versa), realigning a thoroughfare to improve accessibility to surrounding properties and reallocating right of way to better balance design elements among various modes of travel.

General Network Guidelines

Street Spacing Guidelines for Walkable Areas

Local streets should be configured in a fine-grained, multimodal network internal to the neighborhood, with many connections to the system of thoroughfares. Where streets cannot be fully networked, they should be supplemented by pedestrian and/ or bike-pedestrian facilities to provide the desired connectivity.

Pedestrian facilities should be spaced so block lengths in less dense areas (suburban or general urban) do not exceed 600 feet (preferably 200 to 400 feet) and relatively direct routes are available. In the densest urban areas (urban centers and urban cores), block length should not exceed 400 feet (preferably 200 to 300 feet) to support higher densities and pedestrian activity.

Urban Corridor Thoroughfare Planning for Walkable Urban Areas

Corridors are transportation pathways that provide for the movement of people and goods between and within activity centers. A corridor encompasses a single transportation route or multiple transportation routes or facilities (such as thoroughfares, public transit, railroads, highways, bikeways and so forth), the adjacent land uses and the connecting network of streets (Figure 3.5).

Corridor planning is one of the incremental steps for network planning in the long-range transportation plan to thoroughfare design in the project development stage (see Figure 3.5). The purpose of corridor planning is to comprehensively address future transportation needs and recommend a series of physical improvements and operational and management strategies within a corridor. Corridor planning fills the gap between long-range transportation planning and project development. It identifies and provides a link between corridor land-use planning and corridor transportation planning and provides an opportunity to direct future development within the corridor. An important benefit of corridor planning is that it addresses issues prior to reaching the project development stage for transportation improvements within the corridor. Finally, it promotes interagency cooperation and broad stakeholder and public involvement. Corridor plans should address the following: (ID DOT 1998)

Photo image of a major freeway cutting through an urban region. Some of the freeway moves straight through, with some lanes curving away into the lower left corner of the image. The image continues off into the distance, showing how the freeway curves when it reaches a body of water near the urban center.

Figure 3.5 Corridors include multiple transportation facilities, adjacent land uses and connecting streets. Source: Kimley-Horn and Associates, Inc.

The corridor planning process generally mirrors the transportation planning process in its fundamental steps of a needs study, alternatives development, alternatives evaluation and selection of a preferred alternative, which leads to either the developing a detailed plan or implementing the project development process (preliminary design).

Integrating CSS into urban corridor thoroughfare planning requires stakeholders to consider the economic, social and environmental consequences of alternatives. It defines the short- and long-term needs of the corridor, develops goals and objectives that will achieve the vision of the corridor and evaluates feasible multimodal alternatives.

The outcome of CSS in urban corridor thoroughfare planning goes beyond just street improvements. Corridor planning integrally addresses transportation improvement, land development and redevelopment, economic development, scenic and historic preservation, community character and environmental enhancement. Because urban corridor thoroughfare planning affects a broad spectrum of the community, public and stakeholder involvement is a central element of the process. The basic steps in the planning process include:

In some cases, urban corridor thoroughfare planning may be integral with environmental studies leading to a National Environmental Policy Act document (www. epa.gov/compliance/nepa) or other environmental impact assessment. Figure 3.6 illustrates the steps in the corridor planning process and identifies the type of input needed at various stages in the process.

The basic steps in the process, and how CSS principles can be integrated, are described below:

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Figure 3.6 The corridor planning process. Source: Kimley-Horn and Associates, Inc.

(Extended text description: Flow Chart showing Public and Stakeholder Involvement. Corridor Visioning Goals and Objectives Land Use Plans and Long-Range Transportation Plan Network Planning lead with an arrow into Project Need (Long and Short Term) Existing Corridor Characteristics which leads with an arrow to Alternatives Development which leads with an arrow to Alternatives Evaluation (Impacts and Consequences) which leads with an arrow to Preferred Alternative which leads with arrows into Detailed Corridor Plans (Access Management, Scenic Preservations, etc) and Preliminary Design. Data leads with an arrow into Project Need (Long and Short Term) Existing Corridor Characteristics. Evaluation Criteria and NEPA leads with an arrow to Alternatives Evaluation (Impacts and Consequences).)

 

Corridor Vision and Needs

CSS Approach

With a CSS approach, the needs may be stated in terms of context, economic, or other community aspects, as well as mobility needs. The CSS outcome of this step is to provide stakeholders and decision makers (bodies that approve the funding and implementation of projects) with a wide range of choices derived from a collaborative and participatory process. The alternatives should be competitive in that they address as many of the goals and objectives as possible. Solutions should be innovative and flexible in the application of design guidance. The solutions should include ways to enhance and meet the needs of the context, activities generated by adjacent and nearby land uses and objectives that are part of the community vision for the corridor.

Alternatives Development

CSS Approach

CSS Outcome

To the extent not already included in the community vision, consideration should also be given to potential environmental consequences when developing the corridor alternatives. Alternatives may include different alignments and parallel routes, cross-sections, modal combinations, streetside treatments, interaction with adjacent development, streetscape approaches, business and community activity and support infrastructure. The important thing to remember is that the alternatives in CSS are developed to meet the full range of a specific community or neighborhood's objectives.

 

Alternatives Evaluation

CSS Approach

CSS Outcome

 

Mobility for All Users: travel demand, roadway capacity, level of service, travel time, connectivity, circulation, access, truck movement, access to multiple travel modes and so forth.

Social and Economic Effects: socioeconomic and cultural environment (historic, cultural and archaeological resources; environmental justice; residential and business displacement/ dislocation; socioeconomics and equity; neighborhood integrity and cohesion; economic development; place making qualities; and so forth).

Environmental effects: positive and negative effects of natural environment (air quality, noise, energy consumption, water quality and quantity, vegetation, wildlife, soils, open space, park lands, ecologically significant areas, drainage/flooding aesthetics and visual quality); and land use (residential patterns, compatible uses, development suitability according to community values and so forth.).

Cost-effectiveness and Affordability: capital costs, operations and maintenance costs, achievement of benefits commensurate with resource commitment, sufficiency of revenues and so forth.

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Figure 3.7 Corridor planning involves the consideration of trade-offs between alternatives. In this example of a corridor study, different alignments and reconfiguration of streets are evaluated and compared. Source: City of Seattle, CHM2Hill, South Lake Union Transportation Study, Mercer Corridor Project.

(Extended text description: Graphic illustration divided into two sections. The upper section is titled Alternative A. It shows a regular grid-pattern of roadways. There is an area of some kind of land feature at the upper center edge of the illustration. Around this land feature, the roadways are curved to outline the natural shape of the land feature. There is another curving roadway that bisects the rest of the grid pattern. A few of the intersections through the horizontal center of the illustration are highlighted with a dark gray box. There is also a dark line along all the roadways that connect those highlighted intersections. The lower section is titled Alternative B. It shows a regular grid-pattern of roadways. There is an area of some kind of land feature at the upper center edge of the illustration. Around this land feature, the roadways are curved to outline the natural shape of the land feature. There is another curving roadway that bisects the rest of the grid pattern. A few of the intersections through the horizontal center of the illustration are highlighted with a dark gray box. There is also a dark line along the bisecting curved roadway through one of the straight roads and back onto the curved roadway at the right side of the illustration. The dark line connects only a few of the highlighted intersections in the center of the illustration.)

 

Other Factors: compatibility with local and regional plans and policies, constructability, construction effects and so forth.

The alternatives evaluation step includes a comprehensive evaluation of applicable issues and options using selected criteria such as those described above (such as modal capacity; alignment; design concept; costs; right of way; environmental, social and economic impacts; operations; safety; and so forth). Alternatives can be a combination of capital improvements and management and operations strategies. The outcome of this step is the clear communication of trade-offs to the public, stakeholders and decision makers, developed and discussed in a transparent and participatory process.

The selection of a preferred alternative leads to either the development of a detailed corridor plan, such as a thoroughfare plan, access management plan, scenic preservation plan, streetscape plan, or economic vitalization plan. It can also lead to the preliminary design of an individual thoroughfare, network of thoroughfares, or multimodal transportation corridor with parallel thoroughfares, rail, transit, highway and bikeway systems.

Selection of Preferred Alternatives

CSS Approach

Corridor planning varies in level of effort ranging from large-scale planning efforts for corridors in newly developing areas to small-scale planning of segments of individual thoroughfares within constrained rights of way. The outcome of corridor planning ranges from broad policies to statewide and regional long-range transportation plans to multimodal systems plans, as well as to local thoroughfare plans and individual segment concepts and designs (Figure 3.8). CSS plays a role in any type of corridor planning. The remainder of this report focuses on the detailed design of thoroughfares.

CSS Example in Corridor Planning—Developing Evaluation Criteria

SR 179 Corridor Plan

The Arizona Department ofTransportation (ADOT) worked with the community of the greater Sedona area in the Coconino National Forest to design and construct improvements to the 9-mile stretch of SR 179. This road carries millions of tourists each year through one of the most pristine and unique areas of the world. The road is also the only route connecting the business and residential communities of the greater Sedona area. While there have been improvements to SR 179, continuing traffic buildup will continue to exacerbate the capacity and safety issues of the road during the next 20 years.

 

Graphic illustration of a roadway section in an sub/urban setting. The main intersection is a roundabout. The roadway is lined with alternating building, strip shopping centers, parking lots and parks.

Graphic illustration of a major roadway section in a sub/urban setting. The main intersections are square stop light intersections. The roadway is lined with altnerating buildings, strip shopping centers, parking lots and parks.

Figure 3.8 Corridor planning results range from broad policies to detailed concepts for corridor segments. Source: Contra Costa County Dept. of Public Works and Whitlock & Weinberger Transportation, Inc.

This example addresses the selection of evaluation criteria for rural scenic segments and urban segments of the corridor. It is an example of a process that integrates CSS principles to work with stakeholders to evaluate corridor alternatives. The evaluation process could be used to evaluate projects in any context.

The goal of the project was to develop a transportation corridor that addressed safety, mobility and the preservation of scenic, aesthetic, historic, environmental and other community values and to reach consensus on the planning, design and construction of SR 179.

The SR 179 project is a good example of a CSS corridor plan involving the public. The collaborative community-based process used an innovative process called the needs-based implementation plan (Figure 3.9). This process depended on the community to actively participate and provide input throughout the process.

Developing Evaluation Criteria

A unique aspect of the SR 179 Corridor project was the process used to develop and select the preferred planning concepts, particularly the evaluation criteria. The screening process is illustrated in Figure 3.10. The development of evaluation criteria began with working with the community to identify its core values for the corridor. The core values are also components of the vision for the corridor. Core values include in priority order:

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Figure 3.9 The needs-based implementation plan included a community-based process to develop criteria to evaluate corridor alternatives. Source: Arizona Department of Transportation, DMJM+Harris.

(Extended text description: Flow Chart with Core Values: Scenic Beauty, Public Safety, Environmental Preservation, Multi-Modal Corridor, Character, Walkability, Multi-Purpose, Context Sensitivity, Regional Coordination, Economic Sustainability, Mobility with an arrow leading to SR 179 Project Vision with arrows leading to Toolbox: Examples: Signalized intersection, Exclusive turn lane, Raised median, Roundabout and Draft Evaluation Criteria: Examples: Provide safe bicycle crossing and circulation, Minimize the potential for crashes. Both Draft Evaluation Criteria and Toolbox have an arrow leading to Charrette #2: Public Discussion of Evaluation Criteria (Jan 14), Prioritize Evaluation Criteria (Jan 15), and Apply Toolbox to Formulate Planning Concepts (Jan 20).)

 

Using the core values as a base, the project team worked with the community to develop, prioritize and build consensus on criteria for evaluating corridor alternatives. The evaluation criteria and performance measures were used in a screening process to narrow the alternatives to a preferred planning concept for each segment of the corridor. Figure 3.11 presents a sample of the evaluation criteria and associated performance measures.

 

Please see extended text description below

Figure 3.10 The screening process started with a wide range of alternatives and used public participation and evaluation criteria to narrow alternatives to a preferred planning concept. Source: Arizona Department of Transportation, DMJM+Harris.

(Extended text description: Graphic representation of Design Toolbox with categories of Roadway Elements, Transit Elements, Bicycle Elements, Pedestrian Elements, Supportive Facilities in a long horizontal representation of a tool box. Below the toolbox is a descending cone with rings. The toolbox leads into the top of the cone with two lines. The top of the cone is labeled Universe of Planning Concepts. The next level is Fatal Flaw Analysis (12-16 Planning Concepts), followed by Initial Planning Concepts Screening ((6 +/- Planning Concepts), followed by Second Level Planning Concepts Screening (3 +/- Planning Concepts). In a column on the left side of the cone, Roadway Elements bracket the level of Fatal Flaw Analysis. Evaluation Criteria and Performance Measures bracket Initial Planning Concepts Screening and Second Level Planning Concepts Screening.) At the bottom of the graphic is Preferred Planning Concepts with a line leading to underneath the bottom of the cone.)

 

An Important Note About Implementation

The benefits of a highly connected, multimodal network developed through a CSS process will not be fully realized unless the complete network is implemented. Complete implementation requires state, county and municipal transportation agencies to preserve and protect right of way, then fund and construct (or have developers construct) the major and local thoroughfare system.

To gain network benefits early and avoid interim over-sizing of roads, it is important that as development starts, the network should also be constructed in usable segments. For example, when a parcel at the intersection of two county roads is developed, the local street network planned within the development by the MPO, county, or municipality should also be constructed.

Evaluation Criterion Performance Measures
Retain and enhance the natural appearance of the landscape and the ability to enjoy scenic views from the corridor. Number of sensitively placed scenic pullouts
Number of new scenic vistas available
Appropriate scenic viewing opportunity potential
Provide a distinctive corridor identity and unique experience for the user. Opportunity for artistic and landscape amenities
Opportunity to preserve and interpret architectural and cultural themes of the Sedona/Red Rock area
Opportunity for design creativity to contribute to the corridor identity
Provide safe and attractive wayfind-ing aids (signage and informational features) for tourists and others who may be relatively unfamiliar with the corridor. Total number of sites for wayfinding information
Opportunities for context sensitive wayfinding signage visible from the roadway and pathways
Opportunities to provide access to new Forest Service Ranger District Office and other connecting facilities
Provide safe vehicular and emergency access to, from and across the corridor. Number of new safe crossings (signals or roundabouts)
Number of locations on the mainline with left-turn storage lane or roundabout
Number of acceleration and deceleration lanes
Number of "right-in, right-out" ingress/egress locations
Number of mainline entry locations
Provide safe pedestrian crossings and circulation. Number of new safe pedestrian crossings
Opportunities for pedestrian amenities and enhancements at intersections
Square feet of pathways/sidewalks
Number of trailheads directly accessible on foot from the corridor
Number of key destinations in the corridor accessible via a connected pedestrian system

Figure 3.11 Example evaluation criteria and performance measures used in the SR 179 Corridor Plan. Source: Arizona Department of Transportation, DMJM+Harris.

 

Furthermore, at least one street should be constructed and connected through or around the initial development to ensure alternative routes are available in case of emergency, congestion, or temporary blockage.

If this approach continues as development progresses, this implementation approach will ensure that the network will evolve to completion.

Works Cited

Idaho Department ofTransportation. February 1998. Idaho Transportation Department Corridor Planning Handbook. Boise, ID: Idaho Department of Transportation.

Texas Department of Transportation. IH 820 Corridor Alternatives Analysis. Accessible via www.dot.state.tx.us/ftw/mis/ih820/project.htm.

Donohue, Nick, "Secondary Street Acceptance Requirements." 2008. Richmond, VA: Office of the Secretary of Transportation, Commonwealth of Virginia. Accessible via www.virginiadot.org/projects/resources/Spring2008SSAROutreach.pdf.

Transportation Research Board. 2000. NCHRP Report 446, A Guidebook for Performance-Based Transportation Planning. Accessible via http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_446.pdf.

Sources of Additional Information

Arizona Department of Transportation. SR 179 Corridor Project Web site. Accessible via www. scenic179.com/projectoverview/links.cfm. Phoenix, AZ: AZDOT

Center for Urban Transportation Research, University of South Florida. October 1996. Managing Corridor Development—A Municipal Handbook. Tampa, FL: USF.

Federal Highway Administration. Corridor Traffic Management. Accessible via ops.fhwa.dot.gov/program_areas/corridor_traffic_mgmt.htm. Washington, DC: FHWA.

Idaho Department of Transportation. 1998. Corridor Planning Handbook. Boise, ID: Idaho DOT.

Institute of Transportation Engineers.1997. Planning Urban Arterial and Freeway Systems. Washington, DC: ITE.

Institute of Transportation Engineers. 2009. Transportation Planning Handbook 3rd Edition. Washington, DC: ITE.

Kentucky Transportation Cabinet. 2000. Bluegrass Corridor Management Planning Handbook. Frankfort, KY: Kentucky Transportation Cabinet.

Meyer, Michael D. and Eric J. Miller. Urban Transportation Planning, 2nd Edition. Washington, DC: ITE, 2001.

Transportation Research Board. 2003. Access Management Manual. Washington, DC: TRB.

Williams, Kristine M. 2001. Implementing Multimodal Transportation Districts. Center for Urban Transportation Research, University of South Florida. Tampa, FL: USF. Accessible via www2.cutr.usf.edu/pdf/MMTD_Regs_Draft.pdf.

Transportation Research Board. NCHRP Web Document 69, Performance Measures for Context Sensitive Solutions. Washington, DC: TRB. Accessible via http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w69.pdf.

Congress for the New Urbanism. Sustainable Transportation Networks (summary). Chicago, IL: CNU.