Graphics header for Chapter 6 Thoroughfare Designs for Walkable Urban Areas with images of sidewalks, pedestrians and schematics behind the text

Purpose

This chapter identifies how design elements can be combined to produce a thoroughfare in urban walk-able areas with traditional characteristics. This chapter includes tables of common cross-sectional design elements for thoroughfare types in each context zone and provides design examples under various situations. The variation in design criteria are presented by context zone (C-3 through C-5/6), thoroughfare type (boulevard, avenue and street) and whether the thoroughfare serves a predominantly residential or commercial area with fronting ground floor retail.

The design criteria presented in this chapter focus primarily on thoroughfares in walkable areas, but many of the principles and design examples in this chapter are fully applicable to other areas as well.

Objectives

This chapter:

1. Describes how variables such as context zone and land use type can affect the design of thoroughfares; and

2. Provides design examples that guide the practitioner through the design process.

Basis for Thoroughfare Design Examples

The thoroughfare examples illustrate variations in the traveled way and streetside based on the variables of existing right-of-way constraints, context zone, functional classiication, thoroughfare type and predominant surrounding land use and ground floor uses. The general influence of each variable on the design of a thoroughfare is summarized in Table 6.1.

General Walkable Thoroughfare Design Parameters

While walkable thoroughfares can be any functional classification of thoroughfare—arterial, collector, or local—this report addresses only arterial and collector thoroughfares. Within those functional classiications, all three thoroughfare types—boulevards, avenues and streets—may be employed and should be designed to be walkable. The remainder of this chapter provides basic design criteria for developing initial cross-section characteristics. However, despite the presentation of these criteria, designers are reminded that each thoroughfare design is unique, and the ultimate design needs to address the context, objectives, priorities and design concept established for the facility and corridor. Consequently, the thoroughfare designs resulting from use of this guidance may deviate from the initial parameters presented here.

Table 6.1 Effect of Variables on Thoroughfare Design Elements

Variable Effect on Design Elements
Context Zone A designation of design character that affects general design parameters including the selection of thoroughfare type, target speed and the width and treatment of certain streetside elements.
Thoroughfare Type Affects general design parameters of thoroughfares including target speed, number of through lanes, basic travel lane width, medians and the width of certain streetside elements.
Predominant Land Use and Ground Floor Use Divided into predominantly residential or commercial. Residential areas affect streetside width, parking lane width, landscaping and building setback. Commercial, particularly where there is ground floor retail, affects the width of the streetside uses for pedestrian facilities, bus stops, landscaping, outdoor cafes and so forth. Adjacent land uses, pedestrian activity, building orientation and so forth directly influence the target speed (and related design elements).

 

Table 6.2 Selected Characteristics of Walkable Thoroughfares

Characteristic Walkable Thoroughfares Vehicle-Oriented Thoroughfares
Target speed range From Table 6.4. 25-35 mph.
Pedestrian separation from moving traffic Curb parking and streetside furnishing zone. Optional, typically separation achieved with planting strip.
Streetside width Minimum 9 feet (residential) and 12 feet (commercial) to accommodate sidewalk, landscaping and street furniture. Minimum 5 feet.
Block lengths 200-660 feet. Up to one-quarter mile.
Protected pedestrian crossing frequency (pedestrian signals or high-visibility markings at unsignalized crossings) 200-600 feet. As needed to accommodate pedestrian demands.
Pedestrian priority at signalized intersection Pedestrian signals and pedestrian countdown heads, adequate crossing times, shorter cycle lengths and median refuges for very long crossings. Vehicle priority; may have longer cycle lengths and require two cycles for slower pedestrians to cross wide streets with medians.
Pedestrian crossings High-visibility crosswalks shortened by curb extensions where there is on-street parking. Full street width.
Median width 6 feet minimum width at crosswalk, if used as pedestrian refuge, plus 10 feet for left-turn lane, if provided. 14 foot total width for left-turn lane if no refuge needed. 14-18 feet for single left-turn lane; 26-30 feet for double left-turn lane.
Vehicular access across sidewalks 24 feet or less, except if specific frequent design vehicle requires added width. As needed.
Curb parking Normal condition except at bus stops and pedestrian crossings. None.
Curb return radius 10-30 feet; low-speed channelized right turns where other options are unworkable. 30-75 feet; high-volume turns channelized.

 

Table 6.3 Design Elements Influenced by Functional Classification

Characteristic Arterials Collectors
Network Characteristic
Continuity Longer, extending intercity, interarea or serving major corridors. Shorter, connecting neighborhoods and providing local connections to activity centers; usually 1-2 miles.
Trip lengths Longer (local and regional). Shorter (local only).
Role in bicycle network Designated bikeway with bike lanes or shared lanes depending on context and target speed. Bike lanes, signed routes, or shared facilities.
Segment Characteristic
Target speed range (see Table 6.4) 30-35 mph. 25-30 mph.
Traffic volumes (daily) 10,000-50,000. 1,000-10,000.
Transit Major regional fixed guideway corridor, express, or local bus routes. Local bus service only, where provided.

 

For purposes of comparison, Table 6.2 presents some of the common characteristics that should be provided for all walkable thoroughfares and contrasts these characteristics with those of conventional vehicle-oriented thoroughfares.

While the characteristics for walkable thoroughfares of all functional classifications and thoroughfare types have much in common, the thoroughfare's functional classification does influence some of the design characteristics, only a few of which affect cross-section. Table 6.3 compares those design characteristics that vary depending on functional classiication.

Table 6.4 presents the recommended initial cross-section and other design criteria to be used in the design of walkable thoroughfares. Chapters 8

though 10 provide additional criteria and discussion on how and when to use the various design elements. While Table 6.4 focuses on thoroughfares in walkable areas, many of the design elements are applicable in other areas.

Specialized Thoroughfare Designs

This section discusses the design of two specialized types of thoroughfares: main streets and multiway boulevards.

Main Streets

Main streets used to be the principal thoroughfares of American towns, where people could find all types of goods and services. They were the center of commercial, social and civic activities. Main streets thrived up until the 1960s and 70s, when larger-scale, auto-oriented shopping centers became popular. Many communities are revitalizing their main streets to return to a traditional small town mercantile environment or are creating hybrids of traditional and contemporary commercial centers.

Table 6.4 Design Parameters for Walkable Urban Thoroughfares

Thoroughfare Design Parameters for Walkable Mixed-Use Areas
Suburban (C-3) General Urban (C-4)
Residential Commercial Residential
Boulevard [1] Avenue Street Boulevard [1] Avenue Street Boulevard [1] Avenue Street
Context
Building Orientation (entrance orientation) front, side front, side front, side front, side front, side front, side front front front
Maximum Setback [2] 20 ft. 20 ft. 20 ft. 5 ft. 5 ft. 5 ft. 15 ft. 15 ft. 15 ft.
Off-Street Parking Access/Location rear, side rear, side rear, side rear, side rear, side rear, side rear rear, side rear, side
Streetside
Recommended Streetside Width [3] 14.5-16.5 ft. 14.5 ft. 11.5 ft. 16 ft. 16 ft. 15 ft. 16.5-18.5 ft. 14.5 ft. 11.5 ft.
Minimum sidewalk (throughway) width 6 ft. 6 ft. 6 ft. 6 ft. 6 ft. 6 ft. 8 ft. 6 ft. 6 ft.
Pedestrian Buffers (planting strip exclusive of travel way width) [3] 8 ft. planting strip 6-8 ft. planting strip 5 ft. planting strip 7 ft. tree well 6 ft. tree well 6 ft. tree well 8 ft. planting strip 8 ft. planting strip 6 ft. planting strip
Street Lighting For all thoroughfares in all context zones, intersection safety lighting, basic street lighting, and pedestrian-scaled lighting is recommended. See Chapter 8 (Streetside Design Guidelines) and Chapter 10 (Intersection Design Guidelines).
Traveled Way
Target Speed (mph) 25-35 25-30 25 25-35 25-35 25 25-35 25-30 25
Number of Through Lanes [5] 4-6 2-4 2 4-6 2-4 2 4-6 2-4 2
Lane Width [6] 10-11 ft. 10-11 ft. 10-11 ft. 10-12 ft. 10-11 ft. 10-11 ft. 10-11 ft. 10-11 ft. 10-11 ft.
Parallel On-Street Parking Width [7] 7 ft. 7 ft. 7 ft. 8 ft. 7-8 ft. 7-8 ft. 7 ft. 7 ft. 7 ft.
Min. Combined Parking/Bike Lane Width 13 ft. 13 ft. 13 ft. 13 ft. 13 ft. 13 ft. 13 ft. 13 ft. 13 ft.
Horizontal Radius (per AASHTO) [8] 200-510 ft. 200-330 ft. 200 ft. 200-510 ft. 200-510 ft. 200 ft. 200-510 ft. 200-330 ft. 200 ft.
Vertical Alignment Use AASHTO minimums as a target, but consider combinations of horizontal and vertical per AASHTO Green Book.
Medians [9] 4-18 ft. Optional 4-16 ft. None 4-18 ft. Optional 4-18 ft. None 4-18 ft. Optional 4-16 ft. None
Bike Lanes (min./preferred width) 5 ft./6 ft. 5 ft./6 ft. 5 ft./6 ft. 5 ft./6 ft. 5 ft./6 ft. 5 ft./6 ft. 5 ft./6 ft. 5 ft. / 6 ft. 5 ft. / 6 ft.
Access Management [10] Moderate Low Low High Moderate Low Moderate Low Low
Typical Traffic Volume Range (ADT) [11] 20,000-35,000 1,500-25,000 500-5,000 20,000-50,000 1,500-35,000 1,000-10,000 10,000-35,000 1,500-20,000 500-5,000
Intersections
Roundabout [12] Consider urban single-lane roundabouts at intersections on avenues with less than 20,000 entering vehicles per day, and urban double-lane roundabouts at intersections on boulevards and avenues with less than 40,000 entering vehicles per day.
Curb Return Radii/Curb Extensions and Other Design Elements Refer to Chapter 10 (Intersection Design Guidelines)

Table 6.4 Notes:

1. Multiway boulevards are a special form of boulevards. Generally they add one-way, 16-20 foot wide access lanes adjacent to the outer curb and separated from the through traffic lanes by a longitudinal island at least 6 ft. wide (10 ft. if accommodating transit stops). Access lanes have curb parallel parking plus one moving traffic/bike lane with a target speed of 15-20 mph. All vehicular traffic on the access lanes is local. See Chapter 6 section on multiway boulevards for additional information.

2. For all context zones with predominantly commercial frontage, this table shows the maximum setback for buildings with ground floor retail. In suburban contexts, office buildings are typically set back 5 ft. further than retail buildings to provide a privacy buffer. In general urban and urban center/core areas, office buildings are set back 0-5 ft. Setback exceptions may be granted for important civic buildings or unique designs.

3. Streetside width includes edge, furnishing/planting strip, clear throughway, and frontage zones. Refer to Chapter 8 (Streetside Design Guidelines) for detailed description of sidewalk zones and widths in different context zones and on different thoroughfare types. Dimensions in this table reflect widths in unconstrained conditions. In constrained conditions streetside width can be reduced to 12 ft. in commercial areas and 9 ft. in residential areas (see Chapter 5 on designing within constrained rights of way).

4. Desired target speeds on avenues serving C-4 and C-5/6 commercial main streets with high pedestrian activity should be 25 mph.

5. Six lane facilities are generally undesirable for residential streets because of concerns related to neighborhood livability (i.e., noise, speeds, traffic volume) and perceptions as a barrier to crossing. Consider a maximum of four lanes within residential neighborhoods.

6. Lane width (turning, through and curb) can vary. Most thoroughfare types can effectively operate with 10-11 ft. wide lanes, with 12 ft. lanes desirable on higher speed transit and freight facilities. Chapter 9 (Traveled Way Design Guidelines) (lane width section) identifies the considerations used in selecting lane widths. Curb lane width in this report is measured to curb face unless gutter pan/catch basin inlets do not accommodate bicycles, then it is measured from the edge of travel lane. If light rail transit or streetcars are to be accommodated in a lane with motor vehicles, the minimum lane width should be the width of the transit vehicle plus 1 ft. of clearance on either side. Most modern streetcars or light rail vehicles (LRT) can be accommodated in an 11 or 12 ft. wide lane but designers need to consider the LRT vehicle's "dynamic envelope" when designing on horizontal curves and intersections.

Table 6.4 Design Parameters for Walkable Urban Thoroughfares (continued)

Thoroughfare Design Parameters for Walkable Mixed-Use Areas
General Urban (C-4) Urban Center/Core (C-5/6)
Commercial Residential Commercial
Boulevard
[1]
Avenue Street Boulevard [1] Avenue Street Boulevard [1] Avenue Street
Context
Building Orientation (entrance orientation) front front front front front front front front front
Maximum Setback [2] 0 ft. 0 ft. 0 ft. 10 ft. 10 ft. 10 ft. 0 ft. 0 ft. 0 ft.
Off-Street Parking Access/Location rear, side rear, side rear, side rear rear rear, side rear rear rear, side
Streetside
Recommended Streetside Width [3] 19 ft. 16 ft. 16 ft. 21.5 ft. 19.5 ft. 16 ft. 21.5 ft. 19.5 ft. 16 ft.
Minimum sidewalk (throughway) width 8 ft. 6 ft. 6 ft. 10 ft. 9 ft. 6 ft. 10 ft. 9 ft. 6 ft.
Pedestrian Buffers (planting strip exclusive of travel way width) [3] 7 ft. tree well 6 ft. tree well 6 ft. tree well 7 ft. tree well 6 ft. tree well 6 ft. tree well 7 ft. tree well 6 ft. tree well 6 ft. tree well
Street Lighting For all thoroughfares in all context zones, intersection safety lighting, basic street lighting, and pedestrian-scaled lighting is recommended. See Chapter 8 (Streetside Design Guidelines) and Chapter 10 (Intersection Design Guidelines).
Traveled Way
Target Speed (mph) 25-35 25-30 [4] 25 25-35 25-30 25 25-35 25-30 [4] 25
Number of Through Lanes [5] 4-6 2-4 2-4 4-6 2-4 2-4 4-6 2-4 2-4
Lane Width [6] 10-12 ft. 10-11 ft. 10-11 ft. 10-11 ft. 10-11 ft. 10-11 ft. 10-11 ft. 10-11 ft. 10-11 ft.
Parallel On-Street Parking Width [7] 8' 7-8 ft. 7-8 ft. 7 ft. 7 ft. 7 ft. 8 ft. 8 ft. 7-8 ft.
Min. Combined Parking/Bike Lane Width 13 ft. 13 ft. 13 ft. 13 ft. 13 ft. 13 ft. 13 ft. 13 ft. 13 ft.
Horizontal Radius (per AASHTO) [8] 200-510 ft. 200-330 ft. 200 ft. 200-510 ft. 200-330 ft. 200 ft. 200-510 ft. 200-330 ft. 200 ft.
Vertical Alignment Use AASHTO minimums as a target, but consider combinations of horizontal and vertical per AASHTO Green Book.
Medians [9] 4-18 ft. Optional 4-18 ft. None 4-18 ft. Optional 4-16 ft. None 4-18 ft. Optional 4-18 ft. None
Bike Lanes (min./preferred width) 5 ft. / 6 ft. 5 ft. / 6 ft. 5 ft. / 6 ft. 5 ft. / 6 ft. 5 ft. / 6 ft. 5 ft. / 6 ft. 5 ft. / 6 ft. 5 ft. / 6 ft. 5 ft. / 6 ft.
Access Management [10] High Low-Moderate Low-Moderate Moderate Low-Moderate Low-Moderate High Low-Moderate Low-Moderate
Typical Traffic Volume Range (ADT) [11] 15,00050,000 1,50030,000 1,00015,000 15,00030,000 1,50020,000 500-5,000 15,00040,000 1,50030,000 1,00015,000
Intersections
Roundabout [12] Consider urban single-lane roundabouts at intersections on avenues with less than 20,000 entering vehicles per day, and urban double-lane roundabouts at intersections on boulevards and avenues with less than 40,000 entering vehicles per day.
Curb Return Radii/Curb Extensions and Other Design Elements Refer to Chapter 10 (Intersection Design Guidelines)

7. An 8 ft. wide parking lane is recommended in any commercial area with a high turnover of parking.

8. For guidance on horizontal radius—see AASHTO's "green book" section on "Minimum Radii for Low Speed Urban Streets—Sharpest Curve Without Superelevation." Dimensions shown above are for noted target speeds and are found on Exhibit 3-16 (Page 151) in A Policy on Geometric Design of Highways and Streets (2004), assuming a superelevation of -2.0 percent reflecting typical cross slope. Depending on design vehicle, horizontal curves may require lane widening to accommodate large vehicle off-tracking. See AASHTO's section on "Traveled Way Widening on Horizontal Curves" for guidance.

9. See also Chapter 9 for additional detail on medians. For curb to curb intersection crossing distances of 60 ft. or more, medians should be at least 6 ft. wide to serve as a pedestrian refuge, otherwise the median should be at least 4 ft. wide. Where left turn lanes are to be provided, median widths should be increased by the width of the turn lane(s). Where left turn lanes are not needed (e.g., long blocks) median widths may be as little as 4 ft.

10. Access management involves providing (i.e., managing) access to land development in such a way as to preserve safety and reasonable traffic flow on public streets. Low, moderate and high designations are used for the level of access restrictions. A high level of access management uses medians to restrict mid-block turns, consolidate driveways and control the spacing of intersections. A low level of access management limits full access at some intersections, but generally uses minimal measures to restrict access.

11. These ranges of typical traffic volumes are intended to help determine the characteristics of thoroughfares. Volumes can fluctuate widely on all thoroughfare types. These ranges are not intended to establish guidelines or upper bounds for designing thoroughfares.

12. Double-lane roundabouts are not recommended in urban areas with high levels of pedestrians and bicyclists.

 

Photo depicting a main street with several storefronts with a large sidewalk with benches, trees and cars parked along the curb.

Figure 6.1 Buildings on main streets are typically located on small lots and front the streetside. Parking is either located in the rear of the building, on-street, or in nearby public parking facilities. Source: Kimley-Horn and Associates, Inc.

Photo outside a shop or cafe with many plants, customers seated around tables on a broad sidewalk.

Figure 6.2 The design of main streets supports active uses such as social interaction, street cafes, window shopping and strolling. Source: Kimley-Horn and Associates, Inc.

The value of today's main streets is summarized in this quote from Portland, Oregon Metro's Main Street Handbook:

"Main streets flourish because they provide a variety of goods and services, a pleasant community environment and efficiency for those who frequent them. When people do their shopping at a main street, they simply accomplish more with less travel and may find the experience more entertaining."

Creating Quality Main Streets

While main streets vary from community to community, there are some universal characteristics. Main streets may be located in any context zone but are most commonly found in suburban (C-3), general urban (C-4) and urban center (C-5) contexts. They are usually short, walkable segments of arterial or collector streets, often only a few blocks in length. They are within a grid or interconnected system of local streets serving the commercial center of town with short blocks, minimal or no driveways and buildings often served by alleys.

Land uses on main streets consist of compact, mixed-use development, usually with a strong retail and entertainment emphasis on the ground floors and an equal mix of residential and/or commercial ofice or services on the upper floors. The buildings are low-scale (generally one to three stories) and are oriented to the street without setback. Also, they are closely spaced as shown in Figure 6.1. Parking lots or garages are located behind or to the side of buildings. Public parking consists of on-street parking and may include strategically located parking lots or garages that support a "park once" environment.

The design of main streets includes wide streetsides that support active uses such as street cafes, social interactions, strolling and window shopping (Figure 6.2). Main streets, by tradition and design, are pedestrian friendly and may have historic or contemporary urban design features, public spaces, or public art. Main streets typically are no wider than two travel lanes, provide on-street parking and may contain bicycle lanes. Transit consists of local service.

The key ingredients for a successful main street include:

Photo outside some shops and/or a cafe on a broad sidewalk with customers seated at tables, plants, lamps, shaded areas and cars adjecent to the area on a road or parking area.

Figure 6.3 The width of the streetside should be planned to accommodate the activities generated by the adjacent land uses. Source: Kimley-Horn and Associates, Inc.

 

According to a report prepared for the New Jersey Department of Transportation (Scoring Formula for New Jersey's Main Streets, Rutgers University, March 2003) and based on a visual preference survey, the attributes of a main street that positively affect how people view the street include:

Attributes of a main street that negatively affect how people view the street include:

Design Factors That Create Main Street Thoroughfares

The multidisciplinary design team needs to consider a number of factors to create an appropriate main street environment. This process often requires trade-offs, such as balancing trafic throughput with economic development goals.

Traveled Way

In designing the traveled way, there are three important factors to consider: speed, width and parking. Because of the pedestrian-oriented nature of main streets, the target speed should be kept low (25—30 miles per hour) in main street segments, even on thoroughfares designated as principal arterials. This speed not only improves the user's perception of the street but also creates a safer environment, accommodates frequent parking maneuvers and is consistent with restricted sight distances encountered in urban places. The visual interest drivers experience on main streets requires lower speeds.

The width of the traveled way affects users' perceptions of the speed and volume of the street. Wide streets may be perceived as a barrier to crossing where frequent crossings are desired and encouraged. Typically, main streets are two lanes wide with parallel parking on both sides, resulting in a traveled way width of 36 to 38 feet (Figure 6.4) or 44 to 48 feet on streets with bicycle lanes. Wider streets may be required to accommodate angled parking (see discussion on implementing angled parking below). An increased number of travel lanes to three or four may be appropriate based on community objectives, the main street's role in the network, and the existence or lack of parallel thoroughfares.

On-street parking is considered an important design element on main streets. It provides a source of short-term parking for adjacent retail and service uses, buffers pedestrians from trafic, creates friction that slows trafic and produces a higher level of street activity. Parallel parking lane width should be 8 feet to accommodate the high level of parking turnover experienced on main streets.

Photo of a typical main street with two lanes and room for curbside parking, with several cars on the parked or moving on the road, a pedestrian crosing the road. The road is lined with shops, businesses or residential units with a sidewalk.

Figure 6.4 A typical configuration of a main street traveled way. Source: Reid Ewing and Michael King.

 

Main streets, as avenue or street thoroughfare types, should forego raised medians, as they create a physical and visual separation of the two sides of the street in an environment in which pedestrians are encouraged to cross the street frequently. Main streets, as boulevards or any thoroughfare wider than 60 feet, may use medians for pedestrian refuge or turn lanes. Landscaping and urban design elements within the median may be used to provide a unifying theme connecting both sides of the street. Landscaping is an important element of main streets. It serves as an amenity to pedestrians and helps provides a uniform theme, often as part of a planned streetscape. Landscaping on main streets should be designed and maintained so that it enhances the visibility and attraction of storefronts, signs and lighting. On new and redeveloping main streets, the design of building facades and signage should anticipate mature landscaping and accommodate its growth without interfering with visibility.

Common design issues related to main street traveled ways include:

Photo depicting angled parking of cars outside a shady tree-covered sidewalk, in front of shops and/or cafes.

Figure 6.5 Angled parking is used to maximize on-street parking on main streets. On narrow streets, some communities use angled parking on one side and parallel parking on the other, and alternate the arrangement from block to block. Source: Kimley-Horn and Associates, Inc.

 

Streetside

Streetside design features include an appropriate width to accommodate anticipated levels and types of activity. The provision of distinct streetside zones is very important on main streets. The clear pedestrian throughway should be wide enough, at a minimum, to allow two people to walk side-by-side. The frontage zone should allow for window shopping, seating, displays and pedestrian activity at building entrances.

The furnishings zone needs to accommodate many functions, including street trees, planting strips, street furniture, utilities, bicycle racks, transit facilities and public art. If community objectives desire, and regulations encourage restaurants, then ensure the street-side furnishings zone can accommodate potential street cafes.

The edge zone will need to accommodate frequent car door openings, parking meters and signing. Lighting in the streetside should provide both safety illumination of the traveled way and intersections and also pedestrian-scaled decorative light standards illuminating the pedestrian way.

Requirements for Great Streets

Great Streets author Allan B. Jacobs describes the physical qualities that are required to make great streets. He states that most of the qualities are directly related to social and economic criteria and designable qualities for creating good cities; accessibility, bringing people together, publicness, livabil-ity, safety, comfort, participation, and responsibility.

Some of these qualities may be challenging for the thoroughfare designers to quantify in the design, or are outside of the designer's responsibility, thus underscoring the importance of multidisciplinary teams, stakeholder involvement and understanding the community's vision. Jacobs' requirements for great streets include:

For further information on these qualities, refer to Part Four of Great Streets.

Intersections

Main street intersection design should emphasize slow speeds and the management of conflicts through appropriate traffic control and improved visibility. Intersections on main streets should emphasize pedestrian convenience, as these types of streets encourage frequent crossing. Main street intersections should be as compact as possible with short crossing distances, using curb extensions where possible. Curb-return radii should be minimized and based on the design and control vehicles selected (see Chapter 7). Crosswalks need to be allowed on all approaches of the intersection. Midblock crossings are usually not necessary due to short block lengths but may be considered where blocks are unusually long and there is a demonstrated demand to cross. Typical main street intersections would include the following design elements:

A more detailed discussion of the intersection design elements listed above are presented in Chapter 10.

Main Street Design Parameters

Table 6.5 provides general design parameters for commercial avenues and streets in context zones C-3 through C-5 that may be applicable in the design of main streets.

Multiway Boulevards

The multiway boulevard is an alternative to conventional higher-volume, higher-speed arterial streets. This thoroughfare type may be used where the community's objective is to accommodate urban mixed use or residential development and a walkable environment on corridors with high traffic demands. A multiway boulevard combines a central thoroughfare for higher-speed through movements bordered by landscaped medians that separate the central thoroughfare from one-way access lanes on each side of the boulevard. The access lanes provide for slower local traffic, parking, bicycle travel and a pedestrian-oriented streetside and are designed to discourage through traffic. Multiway boulevards may be considered where a community desires to make a very wide arterial street more pedestrian friendly yet recognizes the need to retain traffic capacity.

Characteristics of Multiway Boulevards

The general configuration of a multiway boulevard is a bidirectional central roadway that contains four or more lanes and may be divided or undivided, with one-way access lanes on both sides separated from the central roadway with medians. Characteristics of the central roadway and access lanes include:

(Note 2: Designers are encouraged to consult the MUTCD for the current signing and marking for this configuration. Traffic control device applications of this type are evolving.)

 

Table 6.5 Main Street Design Parameters

Suburban (C-3) General Urban (C-4) Urban Center (C-5)
Commercial Main Streets
Avenue Street Avenue Street Avenue Street
Context
Building Orientation (entrance location) front, side front, side front front front front
Maximum Building Setback 5 ft. 5 ft. 0 ft. 0 ft. 0 ft. 0 ft.
Off—Street Parking Access/Location rear, side rear, side rear, side rear, side rear, side rear, side
Streetside
Recommended Streetside Width 15 ft. 14 ft. 16 ft. 14 ft. 19.5 ft. 16 ft.
Edge Zone 1.5 ft. minimum for operational clearance. Use 2.5 ft. if angled parking is considered. Ensure edge zone is wide enough to accommodate parking meters, utilities and signs.
Furnishings Zone Width 6 ft. tree well 6 ft. tree well 6 ft. tree well 6 ft. tree well 6 ft. tree well 6 ft. tree well
Wider furnishings zone is needed to provide public spaces and if main street uses include the potential for street cafes.
Pedestrian Throughway (minimum) 6 ft. 6 ft. 6 ft. 6 ft. 9 ft. 6 ft.
Frontage Zone 2.5 ft. to 3 ft. minimum to accommodate commercia needed (6 ft. or wider) if potential for street cafes or activity along building fronts. Wider frontage zone is merchandise displays.
Street Lighting Intersection safety lighting, basic street lighting and pedestrian—scaled lighting.
Traveled Way
Target Speed (mph) 25 20—25 25 20—25 25 20—25
Number of Through Lanes 2—4 2 2—4 2 2—4 2
Lane Width 10—12 ft. 10—12 ft. 10—12 ft. 10—12 ft. 10—11 ft. 10—11 ft.
Parallel On—Street Parking Width 8 ft. 8 ft. 8 ft. 8 ft. 8 ft. 8 ft.
Min. Combined Parking/Bike Lane Width 13 ft. 13 ft. 13 ft. 13 ft. 13 ft. 13 ft.
Medians Optional None Optional None Optional None
Bike Lanes (minimum/preferred width) 5 ft./6 ft. 5 ft./6 ft. 5 ft./6 ft. 5 ft./6 ft. 5 ft./6 ft. 5 ft./6 ft.
Access Management Minimize driveways on main streets. Access land uses via cross streets and/or alleys.
Typical Traffic Volume Range (vehicles per day) 5,000— 20,000+ 1,000—15,000 5,000— 20,000+ 1,000—15,000 5,000— 20,000+ 1,000—15,000
Intersections
Curb Extensions
(with on—street parking)
Yes Yes Yes Yes Yes Yes
Minimum Curb Return Radii (if extensions not used) 10—15 ft. 10—15 ft. 10—15 ft. 10—15 ft. 10—15 ft. 10—15 ft.
Roundabouts Not recommended on main streets, except as gateway intersections

Property should be accessed from cross-streets or alleys, although access lanes may be intersected by local streets or consolidated driveways without direct access to the central roadway. Access lanes provide on-street parking that may be associated with curb extensions at intersections or extensions that contain street trees. The width of access lanes is composed of the parking lane (7 to 8 feet) and a shared travel lane (10 to 11 feet). Some fire departments may require wider access lanes. However, for emergency access purposes, buildings may be able to be accessed from the central roadway. The maximum width of an access lane should be 17 feet with parking on one side and 24 feet with parking on both sides.

General Cross-Section Design Parameters and Right-of-Way Requirements

Because of their multiple components, the multiway boulevard typically has greater right-of-way requirements than other types of boulevards. Although street-side and median widths can vary substantially, the minimum right of way for a basic four-lane multiway boulevard is 104 feet, composed of the following elements (see Figure 6.6):

 

Diagram depicting a multiway boulevard is characterized by a central roadway with a pair of one-way access lanes. This type of thoroughfare can combine high vehicular capacity with pedestrian-friendly streetsides.

Figure 6.6 A multiway boulevard is characterized by a central roadway with a pair of one-way access lanes. This type of thoroughfare can combine high vehicular capacity with pedestrian-friendly streetsides. Source: Digital Media Productions.

As an example of a more desirable multiway boulevard width in an urban center (C-5) commercial context, the recommended right of way of a four-lane multiway boulevard, based on the design parameters presented in Table 6.4 and Chapters 8 and 9, would be 149 feet composed of

It may be desirable to provide a raised median within the central roadway to provide for access management, street lighting, trees, pedestrian refuge and left-turn lanes at intersections. The width of a median in the central roadway will vary depending on function (see Chapter 9 for recommended median widths), but would add 4 to 18 feet or more to the right-of-way requirements. Bicycle lanes may also be a part of the central roadway, which would require another 10 feet of right-of-way width.

The right of way of several existing two-way multiway boulevards in the United States ranges from 165 feet (The Esplanade in Chico, CA) to 210 feet (Ocean Parkway in Brooklyn, NY). The differences in width are related to the number of central roadway lanes (four versus six), existence of medians in the central roadway and width of access lanes and access lane medians (Bosselman, MacDonald, Kronemeyer. Environmental Quality of Multiple Roadway Boulevards, Institute of Urban and Regional Development, University of California at Berkeley, 1997). Figure 6.7 is an example of a multiway boulevard that merges the access lane in advance of the intersection (see the next section on intersection design).

Photo depicting a multiway boulevard merges the access lane into the central roadway in advance of intersections. The photo shows two lanes of traffic and pedestrian at an intersection.

Figure 6.7 This multiway boulevard merges the access lane into the central roadway in advance of intersections. Source: Kimley-Horn and Associates, Inc.

Multiway Boulevard Intersection Design

Intersections on multiway boulevards provide one of the most challenging aspects of designing this type of thoroughfare. For successful multiway boulevard design, it is essential that all of the design elements work together to manage the various traffic flows safely.

The most frequent concern about multiway intersection design usually relates to how to control the side access lanes. However, if properly designed, the side access lanes will have low volumes, and potential conflicts will be minimal. Proper geometric design and signing are also needed to communicate which user has the right of way at any given time. The access lanes should not be used to carry vehicles going several blocks along the multiway boulevard. Narrow side access lanes and proper intersection control will discourage through use of the access lanes. Because of the proximity of the access lane to the central roadway, queuing on the cross-streets can block access lanes, and this will further discourage use of the access lanes as through routes. Traffic engineers may also be concerned with conflicts between vehicles turning right from the central roadway and vehicles entering the intersection from the access lane. This is best addressed by having tight corner radii for both the central roadway and the access lanes and good sight lines between the central roadway and the access lanes so the turning driver can avoid a conflict.

At this time there is no widely agreed-upon way to design and operate a multiway boulevard intersection. Multiway boulevards, both old and new, exist in many places in Europe and the United States, and the challenges of the intersections have been addressed in many ways. The traditional design of multiway boulevard intersections is to provide stop control for the access lanes and signalized or stop control for the cross-streets and central roadway (see Figure 6.8). In urban areas, the access lanes are often controlled with traffic signals and sometimes restrict selected movements from both the central roadway and the access lanes. Common traffic control and operational configurations for traditional multiway boulevard intersections are described in Table 6.6 and illustrated in Figure 6.9.

Photo depicting a multiway boulevard provides stop control for the low-volume, low-speed access lanes. The central roadway is controlled by a traffic signal.

Figure 6.8 This multiway boulevard provides stop control for the low-volume, low-speed access lanes. The central roadway is controlled by a traffic signal. Source: Kimley-Horn and Associates, Inc.

 

Alternative Multiway Intersection Designs

Thoroughfare designers have developed a number of alternatives to the traditional multiway boulevard intersection. These alternatives include:

All of the above alternatives disrupt the continuity of the access lane along the length of the boulevard. This is an important factor in considering local circulation, particularly if the access lanes provide for bicycle travel along the corridor.

 

Table 6.6 Traffic Control and Operation Configurations for Multiway Boulevard Intersections

Type of Approach
Control (Refer to Fig. 6.9)
Special Treatments or Movement Restrictions Conditions for Application
A Two-Way Stop Intersection
  • Central roadway uncontrolled
  • Cross-street stop controlled
  • Access lane stop controlled
  • No restricted movements, or
  • Access lane restricted to through-right turn only
  • Low-volume cross-street traffic
  • Moderate-volume central roadway traffic
  • Residential or low-intensity mixed use and commercial areas
B All-Way Stop Intersection
  • Central roadway stop controlled
  • Cross-street stop controlled
  • Access lane stop controlled
  • No restricted movements, or
  • Access lane restricted to through-right turn only
  • Low cross-street traffic volume
  • Low to moderate central roadway traffic volume
  • Residential or low-intensity mixed use and commercial area
C Two-Phase Signalized Intersection
  • Central roadway signalized
  • Cross-street signalized
  • Access lane stop controlled
  • Access lane through and right turns may proceed with central roadway through movement after stop
  • Central roadway right turns may be prohibited
  • Low to moderate cross-street traffic volume
  • Low to moderate central roadway traffic volume
  • Residential or low-intensity mixed use and commercial area
D Multi-Phase Signalized Intersection #1
  • Central roadway signalized
  • Cross-street signalized
  • Access lane signalized
  • Central roadway may have protected left-turn phasing
  • Access lanes restricted to through and right-turn only
  • Access lane proceeds during central roadway through movement
  • Cross-street has permissive turn phasing
  • Central roadway right-turns prohibited
  • Moderate to high cross-street traffic volume
  • Moderate to high central roadway traffic volume
  • High-intensity mixed use and commercial area
E Multi-Phase Signalized Intersection #2
  • Central roadway signalized
  • Cross-street signalized
  • Access lane signalized
  • Central roadway may have protected left-turn phasing
  • Cross-street has permissive turn phasing
  • Access lanes have split phasing, allowing all movements
  • Moderate to high cross-street traffic volume
  • Moderate to high central roadway traffic volume with high volume of left turns
  • High-intensity mixed use and commercial area
F Multi-Phase Signalized Intersection #3
  • Central roadway signalized
  • Cross-street signalized
  • Access lane stop controlled
  • Access lane right turns only may proceed after stop
  • Central roadway has permissive turn phasing
  • Cross-street has permissive turn phasing, and may use split phasing
  • Low to moderate cross-street traffic volume
  • Low to moderate central roadway traffic volume
  • Residential or low-intensity mixed use and commercial area

Design Examples

The following design examples provide a brief synopsis of the design process, illustrating some of the key steps in developing and evaluating solutions to thoroughfare design problems. The examples do not represent all of the possible combinations but do show some common thoroughfare situations. The four examples respectively illustrate the following thoroughfare design scenarios:

1. Creation of a retail-oriented and pedestrian-friendly main street collector avenue;

2. Transformation of an obsolete suburban arterial to a boulevard in a mixed use area;

3. Design of a high-capacity arterial boulevard in a newly urbanizing area; and

4. Four- to three-lane arterial avenue conversion in a central business district.

The design process used in the examples follows the design stages introduced and described in Chapter 5. The design examples provide a general overview of the process to illustrate the five stages of design.

The details of the evaluation and development of the actual design are omitted in the four examples.

Remember Network Potential

In all cases of designing walkable urban thoroughfares, part of the analysis will be to analyze network capabilities, contexts and travel patterns to determine whether and how much the network can accommodate some of the study thoroughfare's existing or projected traffic. This may require operational or physical improvements. However, it may lead to a more contextually desirable improvement and more effective overall solution.

Please see extended text description below

Figure 6.9 Various traffic control and turn restriction options can be employed at multiway boulevard intersections. See Table 6.6. Source: Kimley-Horn and Associates, Inc.

(Extended text description: This diagram contains multiple boxes, each with different arrows indicating central roadway movements, cross street movements, access lane movements and turn restrictions. Box A contains down and up arrows labeled as Uncontrolled, left and right arrows pointing to the text STOP, up and down arrows pointing to the text STOP and a curved left arrow with a strike through it labeled with Option. Box B contains down and up arrows pointing to STOP, left and right arrows pointing to STOP, down/down turn and up/up turn arrows pointing to STOP and a curved left arrow with a strike through it labeled with Option. Box C contains down/down turn, down, up, up/up turn arrows pointing to STOP, left/left turn and right/right turn arrows, a curved left arrow with a strike through it and a curved right arrow with a strike through it labeled with Option. Box D contains turn arrows facing each other in oppostite turn directions, down/down turn, down, up, up/up turn arrows, left/left turn and right/right turn arrows, and a curved right arrow with a strike through it and a curved left arrow with a strike through it. Box E contains turn arrows facing each other in opposite turn directions, down/down turn and up/up turn arrows left/left turn up and down arrows, right/right turn up and and down arrows, up/up turn left/right arrows and down/down turn left/right arrows. Box F contains down turn arrow pointed to STOP, down/down turn arrow, up/up turn arrow, up turn arrow pointed to STOP. The legend shows up and and down arrows next to the text Central Roadway Movements, a left arrow next to the text Cross Street Movements, an up arrow next to the text Access Lane Movements, a right turn arrow with a strike through it next to the text Turn Restrictions. There is also an overhead line diagram included in this larger diagram that depicts an intersection of several roadways.)

 

Design Example #1:

Creating a Retail-Oriented Main Street

Objective

Convert an existing four-lane minor collector street into a commercial-oriented street that supports an adjacent mix of retail, restaurants and entertainment uses on the ground floor.

Stage 1: Review or develop an area transportation plan

Review the area transportation plan to determine how the subject thoroughfare relates to the overall network, types of modes served, functional classification, existing and future operational characteristics and so forth. Collect existing and projected data as necessary.

Existing Street characteristics

Existing street is a four-lane, undivided collector street with the following characteristics (see Figures 6.10 and 6.11).

Stage 2: Understand community vision for context and thoroughfare vision

An existing commercial street in a suburban (C-3) area undergoing change to an urban center (C-5). Emphasizes an active street life that is to be achieved through the mix and intensity of land uses, site and architectural design, with an emphasis on pedestrian facilities and on-street parking.

Stage 3: Identify compatible thoroughfare types and context zones

Existing context is identified by assessing the character and attributes of existing land uses such as building orientation to the street, building height, parking orientation, mix and density of uses and so forth. Future context is determined by interpreting the vision, goals and objectives for the area. Thoroughfare type is selected based on the urban thoroughfare characteristics (Table 4.2 in Chapter 4).

Stage 4: Develop and test the initial thoroughfare design

Desirable Design elements (in prioritized order based on vision)

Factors to consider/Potential trade-offs

Possible Alternative Solutions (see Figure 6.12)

1. Emphasize vehicular capacity by retaining existing four-lane section with 10-foot-wide travel lanes to allow 10-foot-wide sidewalks.

2. Emphasize parking by providing angled parking on one side, parallel parking on the other side and narrowing the two remaining travel lanes.

3. Emphasize parking and wider sidewalks by providing parallel parking on both sides, two travel lanes and 12-foot-wide sidewalks.

4. Emphasize parking and vehicular capacity with parallel parking on both sides, 9-foot-wide sidewalks, two travel lanes and a center turn lane.

In all cases use grid network to divert some traffic from project thoroughfare so reduced number of traffic lanes will suffice. This may require operational or physical improvements to other streets. Traffic to be diverted will depend on travel patterns, context and design of other thoroughfares.

Compare benefits of the four alternatives. Figure 6.13 demonstrates one way of showing such a comparison.

Selected Alternative

Alternative #3:

Stage 5: Develop detailed thoroughfare design

Figure 6.14 shows a rough schematic view of how the selected alternative might be designed.

Solution Design Features

Traveled Way:

Streetside:

Intersections:

Parallel thoroughfares (as needed):

Photo diecpts empty street at a crosswalk in front of a storfront with a sidewalk out front.

Figure 6.10 View of existing street. Source: Kimley-Horn and Associates, Inc.

Diagram depicts existig street cross-section showing the sidewalk 6 feet in width, the street lanes 13, 11, 11, 13 feet, respectively and the other side of the sidewalk 6 feet width.

Figure 6.11 Existing street cross section. Source: Kimley-Horn and Associates, Inc.

Please see extended text description below

Figure 6.12 Alternative street cross sections. Source: Kimley-Horn and Associates, Inc.

(Extended text description: Diagram depicting alternative street cross sections. Alternative 1 has 10 foot sidewalks surrounding four 10 foot lanes. Alternative 2 has 6 foot sidewalks with 18 foot angled parking, 13 and 9 foot travel lanes and 8 foot parallel parking. Alternative 3 has 12 foot sidewalks surrounding 8 foot parallel parking, two 10 foot travel lanes and another 8 foot parallel parking lane. Alternative 4 has 9 foot sidewalks surrounding 8 foot parallel parking 9 foot travel lane, 9 foot turn lane, 9 foot travel lane and another 8 foot parallel parking lane.)

 

Relative Comparison of Trade-Offs

Alternative Parking Sidewalk Width Vehicular Capacity Large Vehicle Accomodation Pedestrian Crossing Width Left Turn Lanes Bike Accomodation Ped. Amenity Accomodation Speed Reduction
Existing -- -- ++ ++ -- -- -- -- --
1 -- ++ ++ -- -- - -- ++ +
2 ++ -- - + ++ ++ -- -- -
3 + ++ - ++ ++ - -- ++ +
4 + - + -- + ++ -- - ++

Score (relative to other alternatives)

++ Good (achieves objectives)

+ Fair

- Poor

-- Fails to meet/achieve objectives

Figure 6.13 Relative comparison of alternative trade-offs. Source: Kimley-Horn and Associates, Inc.

 

Please see extended text description below

Figure 6.14 Schematic plan view of Alternative #3. Source: Kimley-Horn and Associates, Inc.

(Extended text description: The diagram shows a schematic plan view of alternative #3. It includes labels to the following areas: a bus stop area, curb extensions, textured crosswalks, farside curb extension bus stop, treewells, bus shelter, parallel on-street parking, width for street cafes in furnishings zone, and pedestrian scaled lighting. The schematic shows widths of 12 foot sidewalks surrounding 8 foot parking lanes and 20 feet of travel lanes.)

 

Design Example #2: Transforming a Suburban Arterial

Objective

Transform an obsolete suburban arterial into a boulevard serving a mixed-use commercial-oriented street in an area evolving from a typical suburban pattern (C-3) to a mixed environment with commercial activity and walkable development pattern (C-4).

Stage 1: Review or develop an area transportation plan existing Street characteristics (see Figures 6.15 and 6.16)

Existing street is a seven-lane undivided arterial street with the following characteristics:

Stage 2: Understand community vision for context and thoroughfare vision

Community supports higher-intensity, higher-value development in an existing strip commercial corridor, transforming the suburban character of the corridor to general urban (C-4). Redesign of the street to create an attractive, walkable boulevard is a public-sector

investment strategy to stimulate change. The corridor is envisioned to support a diverse mix of pedestrian-oriented retail, office and entertainment.

Stage 3: Identify compatible thoroughfare types and context zones

Stage 4: Develop and test the initial thoroughfare design

Desirable Design elements (in prioritized order based on vision)

Factors to consider/Potential Trade-offs

Alternative solutions (see Figure 6.17)

1. Provide parking, median and minimum-width sidewalks by reducing to four travel lanes.

2. Provide wide landscaped median and sidewalks by reducing to four travel lanes without providing on-street parking.

3. Provide all desirable features, including median, wide sidewalks and parking, by reducing to four travel lanes and acquiring right of way or require private development to dedicate 7 feet.

4. Emphasize vehicular capacity and provide median and sidewalks by retaining six narrower travel lanes without providing on-street parking. Alternatively, the 11-foot outside lanes could be used for curb parking during off-peak periods and converted to travel lanes during the peak. This alternative would not provide curb extensions at intersections.

In all cases use grid network to divert some traffic from project thoroughfare so a reduced number of traffic lanes will suffice. This may require operational or physical improvements to other streets. Traffic to be diverted will depend on travel patterns, context and design of other thoroughfares.

Compare benefits of the four alternatives. Figure 6.18 demonstrates one way of showing such a comparison.

Selected Alternative

Alternative #1:

Stage 5: Develop detailed thoroughfare design

Figure 6.19 shows a schematic view of how the selected alternative might be designed.

Solution Design Features

Traveled Way:

Streetside:

Intersections:

Parallel thoroughfares (as needed):

Photo of existing street with commercial areas and multiple lanes. See description in context and diagrams that follow.

Figure 6.15 View of existing street. Source: Kimley-Horn and Associates, Inc.

Please see extended text description below

Figure 6.16 Existing cross section. Source: Kimley-Horn and Associates, Inc.

(Extended text description: Diagram showing cross-section of existing street. From left to right, it shows the Private Property Setback, and 100 foot cross section in center, comprised of 4 foot area, 15, 12, and 12 foot travel lanes, a center 14 foot turn lane, then 12, 12, and 15 foot travel lanes, a 4 foot area, then another Private Property Setback.)

 

Please see extended text description below

Figure 6.17 Alternative street cross-sections. Source: Kimley-Horn and Associates, Inc.

(Extended text description: Diagrams of alternative street cross-sections: From top to bottom, left to right: Alternative 1: 12 foot sidewalk, 8 foot parallel parking, 11 + 11 foot travel lanes, 16 foot median, 11 + 11 travel lanes, 8 foot parallel parking and 12 foot sidewalk. Alternative 2: 19 foot sidewalk, 11 + 11 foot travel lanes, 18 foot median, 11 + 11 travel lanes, and 19 foot sidewalk. Alternative 3: 19 foot sidewalk, 8 foot parallel parking, 11 + 11 foot travel lanes, 16 foot median, 11 + 11 travel lanes, 8 foot parallel parking, 19 foot sidewalk. Alternative 4: 14 foot sidewalk, 11 + 10 + 10 foot travel lanes, 10 foot median, 10 + 10 + 11 foot travel lanes, and 14 foot sidewalk.)

 

Relative Comparison of Trade-Offs

Alternative Parking Sidewalk Width Vehicular Capacity Large Vehicle Accomodation Pedestrian Crossing Width Left Turn Lanes Landscaped Median Ped. Amenity Accomodation Speed Reduction Right-of-way Acquisition
Existing -- -- ++ ++ -- ++ -- -- -- ++
1 ++ - + + ++ ++ ++ -- + ++
2 -- ++ + + ++ ++ ++ ++ + ++
3 ++ ++ + ++ + ++ ++ ++ + --
4 -- + ++ - -- + -- - - ++

Score (relative to other alternatives)

++ Good (achieves objectives)

+ Fair

- Poor

-- Fails to meet/achieve objectives

Figure 6.18 Relative comparison of alternative trade-offs. Source: Kimley-Horn and Associates, Inc.

 

Please see extended text description below

Figure 6.19 Schematic plan view of Alternative #3. Source: Kimley-Horn and Associates, Inc.

(Extended text description: Schematic plan view of Alternative #3 shows an overhead diagram of (from top to bottom) with High Visibility Crosswalks, Intersection Safety Lighting, Left Turn Bay at Intersections, Farside Bus Stop in Parking Lane, Bus Shelter, Pedestrian Scaled Lighting, Treewells in Sidewalk, Tree Planters in Parking Lane, Landscaped Median.)

 

Design Example #3: High-Capacity Thoroughfare in Urbanizing Area

Objective

Design a thoroughfare in a newly urbanized area that accommodates high levels of traffic and buffers adjacent land uses from traffic impacts.

Stage 1: Review or develop an area transportation plan

Existing Street characteristics (see Figures 6.20 and 6.21)

Existing street is a five-lane undivided arterial street with the following characteristics:

Stage 2: Understand community vision for context and thoroughfare vision

Area plans envision a mix of high-density housing, retail centers and low-intensity commercial uses fronting the street. Because the roadway accommodates high levels of through traffic, access control is desired. The roadway is currently a bicycle route with bicyclists using the paved shoulder, but bicycle lanes are desired to close gaps in the bicycle system. Adjacent properties provide off-street parking, but some fronting residential and commercial uses would benefit from on-street parking. The area will generate pedestrians who desire buffering from adjacent traffic. The area plan calls for a boulevard design including an alternative for a mul-tiway boulevard with fronting access lanes to provide on-street parking and buffer proposed mixed use development with ground floor retail and housing above.

Stage 3: Identify compatible thoroughfare types and context zones

Stage 4: Develop and test the initial thoroughfare design

Desirable Design elements (in prioritized order based on vision)

Factors to consider/Potential Trade-()ffs

Alternative Solutions (see Figure 6.22)

1. Emphasize streetside buffering and provision of bike lanes; provide minimal width median for access control and narrower travel lanes.

2. Implement multiway boulevard with local access streets that provide on-street parking and shared bicycle/vehicle environment. This allows a wider streetside area and removes bicycles from higher-speed roadway. This configuration requires 15 feet of right-of-way acquisition on each side of roadway, or adjacent development dedicates streetside and on-street parking lane.

3. Emphasize landscaped median and bicycle lanes by narrowing streetside. Provides minimal sidewalk width and reduced buffer area.

In all cases use grid network to divert some traffic from project thoroughfare. This may require operational or physical improvements to other streets. Traffic to be diverted will depend on travel patterns, context and design of other thoroughfares.

Compare benefits of the three alternatives. Figure 6.23 demonstrates one way of showing such a comparison.

Selected Alternative

Alternative #2:

Stage 5: Develop detailed thoroughfare design

Figures 6.24 through 6.26 show a schematic view of how the selected alternative might be designed.

Solution Design Features

Traveled Way:

Streetside:

Intersections:

Parallel thoroughfares (as needed):

Photo of view of existing street, showing wide street with two lanes on each side plus a turn lane.

Figure 6.20 View of existing street. Source: Kimley-Horn and Associates, Inc.

Please see extended text description below

Figure 6.21 Existing street cross-section. Source: Kimley-Horn and Associates, Inc.

(Extended text description: Existing Street Cross-Section diagram shows (from left to right): Large landscaped setbacks, 5 foot sidewalk, 8 foot shoulder, 13 + 12 foot travel lanes, 14 foot turn lane, 12 + 13 foot travel lanes, 8 foot shoulder, 5 foot sidewalk, and some front buildings.)

 

Please see extended text description below

Figure 6.22 Alternative street cross-sections. Source: Kimley-Horn and Associates, Inc.

(Extended text description: Diagram of alternative street cross-sections which include (from top to bottom, left to right): Alternative 1: 6 foot sidewalk, 8 foot lane, 6 foot bike lane, 11 + 11 foot travel lanes, 6 foot median, 11 + 11 foot travel lanes, 6 foot bike lane, 8 foot lane, 6 foot sidewalk. Alternative 2: 9 foot sidewalk, 13 foot parking/bike lane, 9 foot local access lane, 8 foot raised area, 11 + 11 + 11 + 11 foot travel lanes, 8 foot raised area, 9 foot local access lane, 13 foot parking/bike lane, 9 foot sidewalk. Alternative 3: 5 foot sidewalk, 6 foot area, 6 foot bike line, 11 + 10 travel lane, 14 foot median, 10 + 11 travel lanes, 6 foot bike lane, 6 foot raised area, 6 foot sidewalk.)

 

Relative Comparison of Trade-Offs

Alternative Parking Sidewalk Width Roadside Buffer Vehicular Capacity Large Vehicle Accomodation Pedestrian Crossing Width Left Turn Lanes Landscaped Median Bike Lanes Speed Reduction Right-of-way
Existing -- -- -- ++ ++ -- ++ -- + -- ++
1 -- - ++ + ++ - - - ++ + ++
2 ++ ++ ++ ++ ++ ++ - ++ ++ + --
3 -- -- + + + + ++ ++ ++ ++ ++

Score (relative to other alternatives)

++ Good (achieves objectives)

+ Fair

- Poor

-- Fails to meet/achieve objectives

Figure 6.23 Relative comparison of alternative trade-offs. Source: Kimley-Horn and Associates, Inc.

 

Overhead diagram/schematic plan view of alternative #2, showing lanes, bike lianes, sidewalk, parking areas.

Figure 6.24 Schematic plan view of Alternative #2. Source. Kimley-Horn and Associates, Inc.

Diagram of Alternative intersection design for Alternative #2. includes, from top to bottom, a bike lane, right turn only slip ramp to throughway.

Figure 6.25 Alternative intersection design for Alternative #2. Source: Kimley-Horn and Associates, Inc.

Diagram of Alternative intersection design for Alternative #2. This variation contains a stop controlled intersection and shows how the bike lane would curve along side the road and turn lane approaching the intersection.

Figure 6.26 Alternative intersection design for Alternative #2. Source: Kimley-Horn and Associates, Inc.

Design Example #4: Central Business District Four- to Three-Lane Conversion

Objective

Convert an undivided four-lane arterial with parking on one side to three lanes plus parking and bicycle lanes on both sides in a central business district. The purpose of the conversion is to increase on-street parking, provide width for bicycle lanes and remove turning traffic from through lanes.

Stage 1: Review or develop an area transportation plan

existing Street characteristics (see Figures 6.27 and 6.28)

Existing street is a four-lane undivided arterial street with the following characteristics:

Stage 2: Understand community vision for context and thoroughfare vision

The central business district is not envisioned to change significantly in terms of its context. It will remain the highest-intensity development in the city with a mix of commercial uses, ground floor retail and office above. The district has very high levels of pedestrian and transit use; however, new high-rise residential development is increasing the downtown population. There is continued demand for on-street parking and an anticipated increase in pedestrian and bicycle travel as new residents increase 24-hour activities. The city has been implementing its bicycle plan over time by adding bicycle lanes to many of the arterial streets. The traffic engineering department continues to look for opportunities to improve intersection operations and pedestrian safety by adding left-turn bays, curb extensions and protected-only left-turn signal phasing.

Stage 3: Identify compatible thoroughfare types and context zones

Stage 4: Develop and test the initial thoroughfare design

Desirable Design elements

Photo of view of existing street. Road has extensive buildings along the side, with parallel parking areas and several cars stopped at intersection.

Figure 6.27 View of existing street. Source: Kimley-Horn and Associates, Inc.

Factors to consider/Potential trade-offs

Alternative Solution (see Figure 6.29)

Only one alternative design is considered in this design example:

1. Reduce number of through lanes to one in each direction; add an alternating center turn lane, on-street parking and bicycle lanes on both sides. Implement curb extensions at intersections. Retain existing streetside width.

In all cases the existing grid network may need to divert some traffic from project thoroughfare so a reduced number of traffic lanes will suffice. Traffic diversion could require operational or physical improvements to other streets.

Compare benefits of the existing and alternative conditions. Figure 6.30 demonstrates one way of showing such a comparison.

Selected Alternative

Alternative #1:

Stage 5: Develop detailed thoroughfare design

Figure 6.31 shows a rough schematic view of how the selected alternative might be designed.

Solution Design Features

Traveled Way:

Streetside:

Intersections:

Parallel thoroughfares (as needed):

Diagram of existing cross-section which includes, from left to right: 20 foot sidewalk, 13 + 12 + 12 + 13 travel lanes, 10 foot parking lane, 20 foot sidewalk.

Figure 6.28 Existing street cross-section. Source: Kimley-Horn and Associates, Inc.

 

Diagram of Alternative street cross-section, featuring, from left to right: 20 foot sidewalk, 8 + 5 parking/bike area, 11 foot travel lane, 12 foot turn lane, 11 foot travel lane, 5+ 8 parking/bike lane, 20 foot sidewalk.

Figure 6.29 Alternative street cross-section. Source: Kimley-Horn and Associates, Inc.

 

Relative Comparison of Trade-Offs

Alternative Parking Sidewalk Width Capacity and Intersection Operations Large Vehicle Accomodation Pedestrian Crossing Width and Safety Left Turn Lanes Bike Lanes Speed Reduction
Existing + ++ + + + -- -- --
1 ++ + - + ++ ++ ++ ++

Score (relative to other alternatives)

++ Good (achieves objectives)

+ Fair

- Poor

-- Fails to meet/achieve objectives

Figure 6.30 Relative comparison of alternative trade-offs. Source: Kimley-Horn and Associates, Inc.

 

Diagram of Schematic plan view of Alternative #1 -- shows bike lanes, parking travel lanes and turn lane as described previously.

Figure 6.31 Schematic plan view of Alternative #1. Source: Kimley-Horn and Associates, Inc.

Works Cited

Jacobs, Allan. Great Streets. MIT Press. 1993.

Sources of Additional Information

Jacobs, A., Macdonald, E. and Rofe, Y. 2002. The Boulevard Book: History, Evolution, Design of Multi-Way Boulevards. Cambridge, MA: MIT Press.

Jacobs, A., Macdonald, E. and Rofe, Y. 1995. "Multiple Roadway Boulevards: Case Studies, Designs, Design Guidelines." Working Paper No. 652. Berkeley, CA: University of California, Berkeley—Institute of Urban and Regional Development.

MacDonald, Elizabeth. "Building a Boulevard." Access, issue number 28. Spring 2006.

Rosales, Jennifer. Road Diet Handbook: Setting Trends for Livable Streets. PB 2004. William Barclay Parsons Fellowship, Monograph 20, Second Edition, 2007.

Main Streets: Flexibility in Design and Operations. State Guidelines and Standards California Department of Transportation. Accesible via www.dot.ca.gov/hg/oppd/guidance.htm.

When Main Street is a State Highway: A Handbook for Communities and Designers. Maryland Department of Transportation, State Highway Administration. Ac-cesible via www.sha.state.md.us/ohd/mainstreet.htm.

Oregon Department of Transportation. 1999. Main Street.. .When a Highway Runs Through It: A Handbook for Oregon Communities. Portland, OR: Oregon Department of Transportation.