A new chapter for Florida street design
Note: This article is published in the October-November 2012 issue of Better! Cities & Towns (subscribe).
Like many states, Florida has been a source of design guidance and regulations for local government streets and land use. The State of Florida has a regulatory document that is used by most local governments for development and thoroughfares titled “The Manual of Uniform Minimum Standards for Design Construction and Maintenance for Streets and Highways,” more commonly known as “The Florida Greenbook.” The Greenbook, updated every two years, is adopted through the state rule making process and consequently is a regulatory document backed by Florida law.
The Greenbook, developed by professional engineers representing every geographic district in the state, has historically supported conventional suburban development patterns and highways. The 2012 Greenbook includes a new chapter, number 19, titled “Traditional Neighborhood Development.”
The Traditional Neighborhood Development (TND) chapter was developed using guidance from the current AASHTO Greenbook and the 2004 AASHTO document, “A Guide for Achieving Flexibility in Highway Design.” Despite language in the AASHTO Greenbook concerning the flexibility allowed in the manual, most engineers and transportation agencies have not exercised that flexibility. A common misunderstanding of engineers is that the criteria is based primarily on safety. However, the criteria is based significantly on maintaining the design speed and capacity of highways.
The TND chapter, which took two years to write and review, supports the compact development patterns embraced by the Congress for the New Urbanism. Having a regulatory document that endorses narrow lanes, reduced street widths, on-street parking, and the compact urban development patterns necessary for walkable neighborhoods removes potential resistance from design professionals who have seen narrow lanes and other such treatments as increasing their exposure to tort liability claims.
In additional to the TND chapter, a separate document titled the Traditional Neighborhood Development Handbook was created. The Handbook is not a regulatory document, but is intended to be an educational tool for planners and engineers and includes best practices, definitions, planning guidance, and tools that should create walkable, compact development patterns with a highly connected network of streets. The TND Handbook is highly illustrated to clearly provide examples for practitioners who may be new to the New Urbanism. Since it is not a regulatory document, it does not have to go through the rulemaking process and can be updated on an annual basis.
The TND chapter and Handbook promote interconnected, low speed streets through the use of smaller blocks, on-street parking, 9- to 11-foot lane widths, smaller curb return radii, sidewalks at the back of curb, and buildings at the back of sidewalk. Standards for yield streets are also provided.
There were concerns from the Committee about potential misuse of the criteria, therefore reducing developer costs while creating conventional suburban development patterns. Consequently, principles were established which could be used to evaluate proposed development plans. The principles from the TND chapter are listed below.
Based on the Greenbook TND chapter, a project or community plan may be considered a TND when at least the first seven of the following principles are included:
1. Has a compact, pedestrian-oriented scale that can be traversed in a five to ten-minute walk from center to edge.
2. Is designed with low speed, low volume, interconnected streets with short block lengths, 150 to 500 feet, and cul-de-sacs only where no alternatives exist. Cul-de-sacs, if necessary, should have walkway and bicycle connections to other sidewalks and streets to provide connectivity within and to adjacent neighborhoods.
3. Orients buildings at the back of sidewalk or close to the street with off-street parking located to the side or back of buildings, as not to interfere with pedestrian activity.
4. Has building designs that emphasize higher intensities, narrow street frontages, connectivity of sidewalks and paths, and transit stops to promote pedestrian activity and accessibility.
5. Incorporates a continuous bike and pedestrian network with wider sidewalks in commercial, civic, and core areas, but at a minimum has sidewalks at least five feet wide on both sides of the street. Accommodates pedestrians with short street crossings, which may include mid-block crossings, bulb-outs, raised crosswalks, specialty pavers, or pavement markings.
6. Uses on-street parking adjacent to the sidewalk to calm traffic, and offers diverse parking options, but planned so that it does not obstruct access to transit stops.
7. Varies residential densities, lot sizes, and housing types, while maintaining an average net density of at least eight dwelling units per acre, and higher density in the center.
8. Integrates at least ten percent of the developed area for nonresidential and civic uses, as well as open spaces.
9. Has only the minimum right of way necessary for the street, median, planting strips, sidewalks, utilities, and maintenance that are appropriate to the adjacent land uses and building types.
10. Locates arterial highways, major collector roads, and other high-volume corridors at the edge of the TND and not through the TND.
Getting everyone on the same page
Once the goal to create TND development is established, it is critical that all of those involved have the same understanding of the elements necessary to execute a well planned community. Many engineers and planners have been planning and designing conventional suburban developments for decades and have very little understanding of what is considered “urban” or compact development patterns. In order to provide some education and understanding of these concepts, the basis of the context for planning and design contained in both documents is the Transect. The Transect, which is contained in the SmartCode, is used in form based codes by many New Urbanists.
In the TND chapter and Handbook, the Transect is illustrated with examples of the development for the various Transect Zones. These illustrations and examples are intended to be a guide to help engineers and planners understand context as a basis for proper compact development patterns, both adjacent to and within the transportation right of way.
Once the context is established and when the plan is in the development stage, determining how streets should be designed to support the context must be established. Historically, AASHTO Greenbook language concerning design speed was to “use as high a design speed as practical to attain a desired degree of safety, mobility, and efficiency.” The major departure from that conventional suburban street and highway design in the TND chapter is the emphasis on low-speed streets and the elements necessary to create them without law enforcement or vertical traffic calming features such as speed bumps.
Language in the TND chapter states “the goal for TND communities is to establish a design speed that creates a safer and more comfortable environment for pedestrians and bicyclists, and is appropriate for the surrounding context. Design speeds of 20 to 35 mph are desirable for TND streets. Alleys and narrow roadways intended to function as shared spaces may have design speeds as low as 10 mph.” Each of the geometric elements of street design including lane widths such as in the table on page 8 are included in the TND chapter.
While the TND chapter is intended to provide the regulatory framework for TND development, theTND Handbook provides guidance for planning and designing greenfield, urban infill, or redevelopment projects using a compact urban form. It also clearly differentiates between conventional suburban and traditional neighborhood design to maximize the possibility that proper design criteria are used to create well executed TND communities. That’s important, because the street geometry, adjacent land use, and other elements must support a higher level of transit, pedestrian, and bicycle activity. The Handbook should provide planners and designers the educational tools necessary to create the compact urban form needed for successful TND projects.
The TND chapter in the Florida Greenbook and the TND Handbook will now provide local governments in the State of Florida a new approach to creating communities or redeveloping areas that are compact urban with low speed streets that support walking and transit. The web addresses for both documents are included below.
Billy Hattaway is district secretary of the Florida Department of Transportation, District One, in Bartow, Florida. Download the Greenbook at: www.dot.state.fl.us/rddesign/FloridaGreenbook/FloridaGreenbook.pdf. Download the TND Handbook at: ww.dot.state.fl.us/rddesign/FloridaGreenbook/TND-Handbook.pdf