CHAPTER 1 Background

1.1 Introduction

RVAM is an integral part of state departments of transportation ROW management that impacts the structural elements of the road. In light of advances in technology over the past decade, some state DOTs are rapidly updating their tools and technology to assist with planning and maintenance. However, there is a marked difference in the availability of updated technology for managing structural assets versus vegetative assets. The TRB National Cooperative Highway Research Program (NCHRP) Standing Committee on Roadside Maintenance Operations (AKR20) sponsored NCHRP project 14-47 Tools and Technology for Roadside Vegetation Asset Management to increase awareness of the needs surrounding RVAM and to provide a path forward for state DOTs to create or update their roadside landscape asset management (RLAM) plans.

Throughout the research process, particularly during the surveys and case studies, researchers found that the use of the term RLAM caused confusion, as to some audiences, this term excluded turfgrass or other areas that are not considered formally landscaped. As a result, many state DOTs excluded roadside safety features, trees, and turfgrass in their responses. To mitigate this confusion, the research team discussed the terminology with the TRB project panel and determined the phrase RVAM would be used in place of RLAM during the project.

This study took place over two years and evaluated tools and technology currently in use or available to state DOTs for RVAM. The team researched domestic and international DOTs, domestic utility companies, and domestic contractors who provide services to state DOTs.

One of the first items completed during the project was developing a definition for RVAM. RVAM was defined as “the systematic process of developing, operating, maintaining, and measuring vegetative assets’ state of repair, as well as planning for, upgrading, and disposing of vegetation assets in the most cost-effective manner.” State DOTs can use RVAM plans to review completed work or work that is scheduled for completion. Roadside vegetative assets were defined within the project as visible features along the ROW that include vegetation and roadside safety features, such as guardrails, slopes, and sound walls, that affect vegetation maintenance access.

The research team completed two nationwide surveys, a gray-and-white literature review, and five case studies during the first stage of the project. The results of these items are discussed in this report. During the second phase, the research team developed the Tools and Technology for Roadside Vegetation Asset Management Guidebook (Guidebook) to assist state DOTs with updating or upgrading their RVAM processes, a PowerPoint presentation with speaker notes, and a memorandum recommending implementation tasks.

1.2 Structural and Vegetative Assets

Nationally, most state DOTs characterize assets as either structural (e.g., bridges, pavement) or vegetation. This study examined vegetative assets and roadside safety features (e.g., guardrails) and, through the research, sought to determine whether state DOTs can use tools and technology for structural asset management to also manage vegetation and roadside safety features. As roadside safety features are more similar to the structural assets commonly tracked within DOTs than vegetative assets and are directly associated with the safety of the traveling public, this study found DOTs more frequently track these assets.

Assets that fall into both categories, such as roadside vegetative safety features, will be listed as vegetative assets within this report, as management is similar between vegetative assets and roadside vegetative safety features. These safety features are functional vegetative plantings comprised of various types of vegetation that serve the same purpose as some structural assets. An example of a roadside vegetative safety feature is a living snow fence. State DOTs install snow fences along the ROW to reduce snowdrifts; structural versions can be made of metal, plastic, or wood. Vegetation can also be used for snowdrift control. These living snow fences can be made from herbaceous species, or small trees and shrubs, depending on the needs and desires of the state DOT. State DOTs can determine the appropriate type of snow fence based on their goals. Additional roadside vegetative safety features include, but are not limited to:

• Visual screens/buffers
• Sound walls/noise reduction barriers
• Impact attenuators, depending on location and type of plant
• Delineators, depending on location and type of plant

1.3 Benefits and Detriments of Roadside Vegetation Assets

Roadside vegetative assets help support the foundation upon which structural assets are built. Ensuring that the vegetation surrounding roadside safety features is healthy and properly maintained increases the visibility and lifespan of structural assets in the ROW. Healthy, well-maintained vegetation can improve the ROW. For example, the roots of vegetation can prevent erosion, and landslides, thus increasing the resiliency of the roadside. Vegetation can be used as a substitution for structural assets to help reduce maintenance costs as the amount of maintenance needed yearly is less expensive for state DOTs. Vegetative assets can help ensure the lifespan of the structural assets they coexist with on the ROW. Proper vegetation maintenance helps reduce management costs for multiple structural assets—including roadside safety features—by providing stability and support.

In addition to the benefits to roadside safety features and structural assets, vegetation and vegetative assets can also provide benefits such as carbon sequestration, habitat for pollinators and wildlife, aesthetic appeal, shade, water filtration into the soil, stormwater management, wildfire resilience through the removal/control of fire-prone vegetative species, and many other services. Roadside ROWs are corridors that connect wildlife habitats for migration and reproduction. When recommended management practices (RMPs) are followed, the ecosystem services that vegetation provides ultimately save state DOTs money through improved roadside resiliency. These effects can be felt off the ROW through the reduced risk of landslides, fire, flooding, increased use of the ROW for evacuation, and the connection of wildlife areas for conservation. For example, an RVAM approach as outlined in the Monarch Candidate Conservation Agreement with Assurances (Monarch CCAA; U.S. Fish and Wildlife Service 2020) reduces maintenance to accommodate native species.

When vegetation is not properly maintained it can impact the immediate environment, such as contributing to landslides or erosion. Vegetation failure reduces the effectiveness of these assets and can cause structural failure where the assets either break down or become ineffective. For example, the roots of vegetation, such as trees or shrubs, can cause pavement upheaval. Tree failures can block roadways and cause the deterioration of sound walls and other structural assets. Highly flammable invasive plant species such as cheatgrass can contribute to the intensity of wildfires, aiding in fire damage to structural assets, erosion, and landslides. (Colorado State University Extension 2012). Areas that are seeded with native plants with deep roots can increase water infiltration into the soil along the roadside, but areas planted with non-native herbaceous species that have shallow roots can have poor infiltration and can experience more severe flooding and water damage to structural assets, such as buckling pavement or erosion. And vegetation can wrap around guardrails, obscuring their visibility, which can result in damage to the structure.

1.4 Roadside Vegetation Asset Management Funding Barriers

Each state’s DOT funding sources vary over time, and the usage of these funds is dictated by the funding priorities of current administrations—both federal and state. Requirements by the FHWA mandate state TAMP include bridges and pavement (2023). Excluding other assets from TAMPs can cause funding issues for maintaining assets beyond bridges and pavement. Funding opportunities were available from the Moving Ahead for Progress in the 21st Century Act (MAP-21) between 2012 and September 2014. The Fixing America’s Surface Transportation Act (FAST Act) provided funding between 2015 and 2020. The Infrastructure Investment and Jobs Act (IIJA), also known as the Bipartisan Infrastructure Law (BIL), replaced the FAST Act in November 2021 and will expire in 2026. These bills provide(d) pathways for state DOTs to identify and apply for funding; however, this type of funding is only available for short periods (e.g., IIJA/BIL provides funding for five years). With each new funding bill, state DOTs must determine how to allocate the funding provided in the latest bill to meet both national and state priorities.

Funding sources are often created to meet the provisions of the TAMP requirements, and other requirements that state DOTs must follow. Federal funding is available for construction and postconstruction revegetation establishment. Vegetation maintenance, when not tied to postconstruction establishment, is often left to state funding. State DOTs often use the FHWA TAMP requirements as the basis for developing their individual TAMPs. A state DOT can decide to include additional assets and determine stricter requirements for managing these assets or follow the federal guidelines for which assets and requirements to include. Tracking certain structural assets, such as bridges and pavement, is a federal requirement directly associated with public safety; as such, federal funding is provided for these assets to ensure federal compliance and traveler safety.

Due to budget constraints and public safety concerns, state DOTs usually focus on collecting data and locating funding for high-cost, low-quantity assets—such as bridges—over low-cost, high-quantity assets —such as trees (Rasdorf et al. 2009). A low-cost, high-quantity asset is one that is frequently encountered and has an overall small cost to maintain, whereas a high-cost, low-quantity asset is an item that is encountered infrequently and, when maintenance is required, has a high associated cost. Vegetation is often considered a low-cost, high-quantity asset that is not directly tied to safety. As such, these assets typically have low funding within the state DOTs. However, vegetation can be a safety concern to the traveling public when it causes sight-distance issues, obscures safety features, or falls onto the roadway. These safety concerns are difficult to prevent and mitigate without proper funding for planning and tracking or equipment to maintain the vegetation.

Budgetary constraints can lead some state DOTs to prioritize tracking the assets for which they receive federal funding and that are required per their state TAMP. This priority tracking has led to commonly used tools and technology designed for the DOT ROW, which primarily function to track and manage structural assets, while other assets are tracked using technology developed for other sectors, such as agriculture. While technology for these other sectors can be adapted for state DOT use, it takes some ingenuity.

1.5 Research Objectives and Scope

The project included the following tasks:

• Task 1: Literature Review and Nationwide Surveys
• Task 2: Case Studies
• Task 3: Work Plan for the Guidebook
• Task 4: Technical Memorandum
• Task 5: Draft Guidebook and Conduct of Research Report
• Task 6: Interim Report
• Task 7: Final Guidebook and Conduct of Research Report
• Task 8: Final Deliverables

The primary objective of this research was to produce a guidebook that state DOTs can use to update their RVAM tools and technology. The research team aims to provide guidance regarding the systems and methodologies that are effective in updating RVAM plans, including helpful types of technology and recommended interdepartmental support. The Guidebook will provide guidance on how RVAM activities can be incorporated into state TAMPs when desired. RVAM is not a federally required process; as such, funds and staff resources are likely limited. The research team understood that the implementation process and recommended actions must be simple, cost-effective, and versatile to increase adoption across state DOTs. There was an emphasis on ensuring that state DOTs of all sizes and RVAM program statuses could utilize the Guidebook. This includes state DOTs in the process of beginning their RVAM program or those that wish to update their existing RVAM program.

In addition to the Guidebook, the research team developed an Implementation Plan. This plan outlines possible pathways to facilitate the Guidebook’s use and includes the benefits of RVAM; organizations that can support the creation of a pooled fund study to collaborate on updating processes and tools and technology; and funding pathways. These components can help raise state DOTs’ awareness of all options for RVAM development and available updates.

The TRB project panel received updates at the conclusion of each task to ensure the project was progressing on the correct path. TRB project panel comments were incorporated into each task deliverable. Each task’s approach is outlined in the following chapter.

The research team also provided monthly updates to the TRB project panel to ensure TRB project panel approval before moving on to the next task. This guaranteed the project met expectations and objectives as determined by the sponsoring NCHRP standing committee.