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4 Background The UFR presents many challenges for state DOTs. The definition of UFR for this synthesis is roadsides associated with high visibility urban freeways with limited pedestrian access, such as wider medians, interchanges, and overpasses. The design expectation of the UFR is to meet safety requirements, community expectations for aesthetics, sustainability objectives, and an achievable level of maintenance. Rural, suburban, and urban ROWs have varying levels of management and very diverse management strategies and maintenance issues. Community aesthetic expectations for the UFR often involve more ornamental type landscapes that require a greater level of main- tenance. This expectation for park-like roadsides often conflicts with state DOT budgets, and the ability of workers to adequately and safely access and maintain the site. Constant high traffic volumes and difficultly in accessing sites can compromise worker safety. Traffic controls are often required to perform maintenance activities in the UFR environment. State DOTs manage vast areas of roadsides within the ROW not only for the safety of the trav- eling public, but also for the integrity of the roadway infrastructure. Large urban interchanges can consist of areas greater than 100 acres. The U.S. Interstate System envisioned in the 1960s and completed in the 1970s includes, in part, the UFR, as do state highways systems constructed decades ago. The landscape development installed at the time of roadway construction aged with the respective surrounding infrastructure leaving state DOTs with mature vegetation that may be near the end of their life cycle. Deterioration of the roadside through the loss of planted vegetation can lead to erosion problems, thereby compromising the roadway and surrounding infrastructure. Roadways and other infrastructure routinely receive resurfacing, restoration, and rehabilitation as the regional mobility needs change and original material integrity degrades over time. However, the UFR associated with their respective highway systems may not receive the same routine rehabilitation. The UFR and associated urban freeways are a dynamic environment subject to changes over time. Changes to the roadways often involve destruction of the existing UFR. The interchange of Interstate 10 (I-10) and I-610 West in Houston, Texas, was constructed in 1964. It went through a series of renovations and expansions over the years as did the respective UFR. The following images are a chronological record demonstrating the changes to the roadways and roadsides over the course of 54 years. Figures 1 through 6 show the evolution of the interchange at I-10 and I-610 West in Houston, Texas. Figure 1 shows photos taken in 1964 after completion of the original construction with minimal landscape development at the site. Figure 2 shows the I-10 at I-610 West interchange in 2002 (38 years later) immediately before demolition work for roadway changes began. Original trees were primarily seedlings installed by Trees for Houston (nonprofit) over several years. The earliest seedlings installation was in the late 1980s, and additional seedlings were planted in the early 1990s. C H A P T E R 1 Introduction
Introduction 5 Figure 3 shows the I-10 and I-610 West interchange in 2003 following the clearing associated with the reconstruction work. Figure 4 shows the interchange during construction in April 2007. Note that the residual soils for planting vegetation lack topsoil and are essentially a clay embankment soil. Figure 5 shows the interchange in April 2009 several months after replanting. TxDOT planted over 12,000 trees in this interchange location. Figure 6 shows I-10 and I-610 West in 2018, 9 years after replanting the interchange. The UFR is also subject to the same elements as other urban environments. These include the heat generated from the pavement and surrounding buildings and infrastructure, an inhospitable growing environment, interface with public uses, illegal or unauthorized ROW usage, and reduced maintenance budgets. Good communication and a cooperative effort through planning, design, environmental, construction, and maintenance practices are effective for preserving the UFR as a valuable highway system asset. Effective landscape development and management practices have been developed by many state DOTs as they realize the unique scenario that the UFR presents. Each state and ecological Figure 1. Interchange at I-10 and I-610 West in Houston, Texas, completed in 1964 (Slotboom 2003). Figure 2. Interchange at I-10 and I-610 West before 2002 reconstruction (Courtesy of TxDOT).
Figure 3. Interchange at I-10 and I-610 after clearing in 2003 (Courtesy of TxDOT). Figure 4. Interchange at I-10 and I-610 West during construction in 2007 (Courtesy of TxDOT). Figure 5. Interchange at I-10 and I-610 West in April 2009 after replanting (Courtesy of TxDOT).
Introduction 7 region has site-specific vegetation types, soils, site geometry, climate, and other factors that enable healthy, sustainable urban roadsides. Along with the typical roadside activities is the high profile issue of illegal camping and other unauthorized ROW uses that are ever growing in the urban roadside environment. This report explores the current practices, policies, and protocols that exist within state DOTs for designing and managing limited access UFR. Chapter 1 provides the background of the synthesis, highlights the areas of focus, and defines relevant terms used throughout the report. The method for the entire study and more detailed descriptions of the methods used for the individual research tasks are included. This chapter concludes with a description of the organization of the report that briefly describes the outline of the various tasks presented. Scope and Objectives The primary objective of this synthesis is to identify sustainable landscape development and management practices for UFR to help state DOTs evaluate and improve their programs. It also seeks to document existing UFR research and practices. This includes identifying current chal- lenges facing state DOTs that may necessitate technical or administrative requirements to resolve. The scope of this project included gathering data on how state DOTs manage high visibility urban freeways with limited pedestrian access, such as wider medians, interchanges, and overpasses. Method NCHRP Synthesis 539 summarizes current practices by state DOTs through a review of pub- lished literature on UFR sustainable design and maintenance practices, a web-based survey, and follow-up interviews with select respondents that have pertinent information to develop case examples. The survey questions were designed to ascertain which state DOTs had documented design and maintenance procedures that specifically respond to the limited access UFR. The data collected relates to the following issues: â¢ Methods of sustainable urban landscape development and management practices for high visibility urban freeways with limited pedestrian access â¢ Integrated vegetation management plans for urban roadsides Figure 6. Interchange at I-10 and I-610 West in 2018 (Google Earth, TxDOT).
8 Landscape Development and Management Practices for Urban Freeway Roadsides â¢ Maintenance agreements between state DOTs and local entities â¢ Effective landscape development deterrents and other methods for managing the illegal or unauthorized use of the ROW â¢ Work zone safety for maintenance personnel on urban limited access freeways Based on the findings of existing state DOT practice, the synthesis identified gaps in knowl- edge and areas for future research. The study team sent email invitations to participate in the web-based survey questionnaire to the list of AASHTO state maintenance engineers provided through the NCHRP Project 20-05/ Topic 49-06 panel. Thirty-three states responded (66%) regarding their management methods for the UFR. The team sent email reminders with select follow-up telephone calls to obtain as high a response rate as possible. The team contacted agencies identified from the survey that had pertinent information and were willing to participate in follow-up interviews for use as case examples. Terminology Several terms used throughout this synthesis require definition: â¢ Context sensitive solutions and design (CSS): Collaborative, interdisciplinary decision- making process and design approach that involves all stakeholders to develop a transporta- tion facility that fits its physical setting (Federal Highway Administration 2018). â¢ Crime Prevention through Environmental Design (CPTED): Collaborative process that includes relevant stakeholders to a specific project: owners, architects, engineers, planning and land use boards, law enforcement officials, security professionals, and citizens working together to ensure that the built environment maximizes desirable use of the property while simultaneously impeding potential undesirable use and opportunities for criminal activity (Connecticut Housing Finance Authority 2017). â¢ Freeway: High-speed (50 mph +), controlled-access thoroughfares with grade-separated interchanges and limited or no pedestrian access. â¢ Illegal or unauthorized uses of the ROW: Include a range of uses from unpermitted vendors and unauthorized signage to occupied areas established within the ROW. â¢ Integrated vegetation management: Coordinated decision-making and action process that uses the most appropriate vegetation management methods and strategy, along with a moni- toring and evaluation system, to achieve roadside maintenance program goals and objectives in an environmentally and economically sound manner (Robertson and Smith 2011). â¢ Intelligent Transportation Systems (ITS): Integration of advanced communications tech- nologies into transportation infrastructure and into vehicles. ITS encompasses a broad range of wireless and traditional communications-based information and electronic technologies (U.S. Department of Transportation 2018). â¢ Interchange: System of interconnecting roadways providing for traffic movement between two or more highways that do not intersect at grade (Manual on Uniform Traffic Control Devices 2009). â¢ Landscape development: Roadside design may include, but is not limited to, revegetation, landscape plantings, erosion control, green infrastructure, slope restoration, wild flowers, hardscape, and other aesthetic treatments. â¢ Median: Area between two roadways of a divided highway measured from edge of traveled way to edge of traveled way. The median excludes turn lanes. The median width might be different between intersections, interchanges, and at opposite approaches of the same inter- section (Manual on Uniform Traffic Control Devices 2009).
Introduction 9 â¢ Urban: As defined by the places within boundaries set by the responsible state and local offi- cials having a population of 5,000 or more. Urban areas are further subdivided into urbanized areas (population of 50,000 or more) and small urban areas (population between 5,000 and 50,000) (AASHTO 2011). â¢ Work zone safety: Methods used to protect personnel as they perform maintenance activities. Organization of Report The report has the following five chapters: â¢ Chapter 1 presents the project background, scope and objectives, method, terminology, and report organization. â¢ Chapter 2 contains the literature review of the issues related to the UFR. â¢ Chapter 3 summarizes the state-of-the-practice survey responses and documented state DOT UFR policies, practices, and protocols. â¢ Chapter 4 presents the case examples of successful implementation of sustainable UFR practices. â¢ Chapter 5 concludes with a summary of the overall findings and suggested research to advance the state of the practice. The findings and discussion reflect the results of the questionnaire and follow-up interviews. The recommendations are limited to suggestions for future research. Appendix A contains the survey questionnaire. Appendix B contains a list of the survey respondents. Appendix C contains the survey results. Appendix D shows examples of policies, procedures, and practices used by state DOTs for illegal or unauthorized use of the ROW. Appendix E has examples of imple- mented safe work zone practices. Appendix F contains cooperative agreements for landscape development and maintenance between state DOTs and other entities or agencies.