CHAPTER 3
Why Implement Roadside Vegetation Asset Management?

3.1 Introduction

The nationwide surveys conducted for the project (both initial and targeted) revealed overwhelming support within the state DOTs for increasing the use of tools and technology for roadside vegetation asset management tasks. Thirteen of the twenty-eight initial surveyʼs respondents stated their organization did not have a roadside vegetation asset management plan. Of the respondents to the targeted survey, 10 DOTs stated that mapping was improved, 7 stated that vegetation planning was improved, 9 stated maintenance operations logistics was improved, and 9 stated data tracking was improved by the data and information obtained using tools and technology. However, respondents to the targeted survey stated that the improved data and information obtained using newer tools and technology either did not reduce the time needed for staff training for vegetation management overall or had increased the number of hours spent by staff. (See Applying Commercial Software and Technology for State DOT Purposes section of this chapter and NCHRP Web-Only Document 429 for more information.) The responses regarding the use of tools and technology show state DOTs predominantly benefit from the use of tools and technology. During the targeted surveys, states indicated that landscape and vegetation management are usually the last priority for funding and task completion. State DOTs corroborated this during the case studies by explaining the lack of federal funding available for these assets. However, targeted survey responses showed many state DOTs want to increase the priority of roadside vegetation asset management compared to the current levels of prioritization. In addition to the lower priority for roadside vegetation asset management tasks compared to structural assets, states indicated they have only recently begun using geospatial mapping for structural assets. There is an overlap between the state DOTs actively using geospatial mapping for structural assets and those researching this technology for roadside vegetation asset management.

Common issues occur when state DOTs do not prioritize vegetation management and roadside safety feature management along the right-of-way. When management is lacking or absent for these assets, resulting challenges can include insufficient funding, difficulty implementing new tools and technology, insufficient available dedicated and trained staff, poor vegetation establishment due to poor soil nutrients, insufficient IT and other staff support for new equipment/technologies, issues with management software and field equipment, and a lowered resiliency of the roadside.

With tools and technology in place, state DOTs can assess and measure their roadside maintenance departmentsʼ needs more accurately. State DOTs can see where they are falling short of meeting goals and where improvements are needed. Tools and technologies can provide state DOTs with data to demonstrate funding needs.

3.3 Staff Retention

State DOT staff can transfer to departments and locations within the organization. When employees receive additional training, they become eligible for promotion and are more appealing to other employers. State DOT staff promotions, while good for employee morale and overall state DOT staff retention, can leave local offices short-staffed. Among the three targeted survey respondents, two indicated that staff availability was an issue that prevented vegetation management objectives from being met.

State DOT staff interviewed for the case studies stated that employee retention improved when morale increased and when local staff felt more connected to the work that they completed. When employees were able to readily see vegetation maintenance progress through consistent georeferenced documentation, they felt a morale boost because they felt more connected with the work and took ownership of the work performed.

Another way to increase staffing at the local level is to incorporate pay progression for staff who obtain additional certifications and licenses related to vegetation maintenance (e.g., pesticide licenses). Pay progression can increase staff retention, which can help increase the number of staff who are highly trained within the local units. These experienced and fully trained employees will be more effective and efficient than new hires at completing roadside vegetation asset management tasks. Experienced employees can improve new employee training and mentoring and reduce new employee training costs while new staff learn safe, efficient, and effective methods for completing roadside vegetation asset management.

3.4 Improvements to Technology

Over the past 10 years, technology has rapidly advanced and many state DOTs have updated their tools and technology to reflect this. Some technologies (e.g., geospatial technology, remote-sensing and monitoring technologies; mobile devices and software applications; and nondestructive evaluation methods) are being used more frequently to measure, monitor, and document vegetation assets. New technology (e.g., AI paired with multispectral cameras) is being pilot-tested for measuring, monitoring, and planning vegetation and for maintenance work for roadside vegetation safety features. This technology is proving successful with stable structural assets; however, the developers of such technology are finding that seasonal changes in growth patterns and coloration make applying this technology to vegetation challenging. Some companies are beginning to investigate using AI to help identify vegetation issues, with some looking into identifying vegetation at the species level, especially for invasive plants. In addition to technology that can identify vegetation, mapping software can now automatically upload updated maps created in the field to a geodatabase accessible across the organization. Although these AI systems are being developed and tested, they are not yet standard at any state DOT.

Applying Commercial Software and Technology for State DOT Purposes

Many types of off-the-shelf (OTS) equipment and technology are available for vegetation management; however, such systems often need modifications for state DOTs to use them. Vegetation management contractors who complete work for state DOTs may have access to newer, commercially available systems that can be helpful to state DOTs. Using contractors with newer technology can enable state DOTs to test new equipment along the right-of-way without (1) purchasing the tools and technology and (2) training staff on the use of the technology. To encourage the use of new technologies, state DOTs may want to adjust their equipment procurement requirements to remove obstacles to purchasing equipment successfully tested in the right-of-way.

States using tools and technology for roadside vegetation asset management tasks may be able to decrease the time and effort staff need for maintenance task recordkeeping. Using technology may not reduce the hours needed for asset maintenance for either structural or vegetation assets, however, because the hours may be reallocated to managing the technological systems in addition to current maintenance workloads—maintenance staff report there is not enough time to complete currently assigned vegetation maintenance work. As a result, state DOTs can expect that overall hours for roadside vegetation asset management work will remain the same.

Global Positioning Systems/Automatic Vehicle Location Systems

Using global positioning systems/automatic vehicle location (GPS/AVL) systems within vehicles allows state DOT staff to automatically track where vehicles are throughout the day, thus enabling state DOTs to more easily identify where herbicide application, mowing, and other roadside vegetation asset management tasks have been completed or need to be completed. This more complete picture of right-of-way management allows state DOTs to increase efficiency and more accurately budget for roadside vegetation asset management tasks. GPS/AVL systems have been widely tested and used by state DOTs and have provided large amounts of accurate data over the years.

If adequate funding is available, GPS/AVL technologies can be used in conjunction with data management systems. Data management systems enable state DOT staff to have in-cab control of herbicide application nozzles and can provide real-time tracking of herbicide application trucks. Technology to assist with data management can automatically map locations where herbicide is applied as well as provide spray records. Maps can be automatically uploaded into the state DOTʼs cloud-based server and added into the statewide GIS. Office staff can subsequently map and identify areas to treat, shifting some of the burden associated with field work to office staff. This reduces (1) the time staff spend on the right-of-way writing locations on paper and transferring the information into a computer system, (2) the number of data entry errors, and (3) the time required of staff members to verify that information has been transferred accurately. These data management systems can assist with vegetation maintenance operations by tracking the spread and control of invasive plant species and can help prevent accidental herbicide application.

Recordkeeping

Ideally, state DOTs keep records of all maintenance work. Creating these records enables central office and local staff to assess what type of work can be accounted for each year. Such records also help when the central office is reviewing what type of equipment to purchase for the upcoming season. Georeferenced, computer-based herbicide application systems and associated time-stamped records can be used to help with customer service responses and with litigation cases against the state. For example, herbicide application records are mandated; if applications are incorporated into a statewide tracking system, this information can assist if a landowner decides to pursue litigation against the state DOT. Common litigation reasons include herbicide damage to crops or turfgrass or the removal of a tree on the landownerʼs property. Georeferenced and time-stamped records allow state DOTs to state definitively whether they were at the site and what work was completed. Georeferencing work completion can decrease the amount of time state DOTs spend locating information to resolve complaints and refute legal claims, as needed.

Staff Acceptance

Although state DOTs can benefit from adapting new tools and technology, lack of acceptance by staff can undermine those benefits. Buy-in is needed from IT staff, local field staff, district

staff, and upper management. This support will ensure the purchase of tools and technology and that staff can and will use them in the field. Upper management needs to approve the purchase and use of equipment, and IT staff must be able and willing to facilitate the successful roll-out of the tools and technology and support all immediate and future needs that arise from adapting the tools and technology. District staff may push the local staffʼs needs up to upper management and upper managementʼs agenda down to the local staff. Finally, local field staff must be willing and able to use the new tools and technology in the field. All state DOTs that have implemented new technologies (e.g., mapping software) stated that delayed IT response time was an issue. Additionally, if local staff do not use the technology frequently (due to seasonal and varied workloads as opposed to being on a dedicated crew) or if there is a steep learning curve and a lack of accountability from central office staff and local management, staff may not support the use of such equipment. These factors can lead to reduced numbers of state DOT staff who are willing to test and become proficient with new tools and technology.

Ensuring IT Staff Support

Before purchasing tools and technologies for roadside vegetation asset management, purchasing managers may work with IT staff to identify the requirements for IT support, data storage, and manufacturing location for the new tools and technology. Multiple states that participated in the surveys and case studies stated that the state DOT had requirements for the type of IT support (in-house or a third party). State DOTs responding to the targeted surveys provided various responses when asked whether there were requirements to procure software and/or hardware solely from U.S.-based manufacturers; for those DOTs with known location-based manufacturer requirements, most identified U.S.-based companies as preferable for software and/or hardware procurement. State DOT staff will want to research storage location requirements and whether data can be stored off DOT property before acquiring new tools and technology. If data can be stored off DOT property, state DOT staff can determine whether the state has requirements for off-site storage (e.g., security or the location of the servers).

3.5 Staff and Equipment Management

Communications with multiple state DOTs revealed that staff and equipment management is often hampered by insufficient or poor communication. Tools and technology can be used to ensure staff communicate where work is needed and when it has been completed. Tracking software can monitor equipment use and location when equipment is rotated among state DOT offices. The use of tracking software can alleviate the common communication issues that arise regarding the location and duration of equipment use. Using technology to track the location and use of equipment can enable state DOT staff to identify when equipment needs to be purchased, sold, or transferred between counties, which can ultimately reduce costs for the state DOT. Adopting new tools and technology can help refine staffing and equipment use and allocation to best serve the needs of the state DOT.

Tools and technology can also be used to ensure that (1) staff time is tracked and (2) this information can be exported into the business analytics platform that the agency uses. Some streamlined systems can also track equipment use for export and analysis. All of the case study DOTs stated that their management software was either PCCA or fully proprietary. For such software to be effective, IT staff members are assigned to assist management staff with software issues and questions, ensure that the software is working properly, and push updates out promptly. One case study DOT stated that the operating system their proprietary management software is using was outdated and IT could not maintain the system, leaving staff trying to use a software system that had not been updated in over 5 years. The state DOTs with dedicated IT staff stated

that their management software was updated regularly, and as a result, functions well. Some of the software systems mentioned are over 10 years old but are current because of regular updates from the IT department.

Tools and technology can help ensure all work is tracked correctly, thus reducing the amount of time needed for quality control. Departments that integrate modern technology can benefit from tools that automatically track and upload completed RVAM work and work locations into a statewide mapping system, helping central office staff determine the amount of time each task required in previous years to plan project workloads and can ensure budgets include enough funding for all tasks that state DOT staff complete throughout the year.

Many of the case study state DOTs the research team spoke with stated that, without IT support, they expected their management software to last 5 years. With IT support, these systems are constantly updated to ensure continued use without diminished capabilities.

3.6 Vegetation Management

State DOTs often undervalue vegetation management compared with structural asset management. This may be because there may not be much noticeable change after vegetation management has been completed—roadside vegetation assets are managed to ensure the continuity of the asset condition as opposed to updating the condition of the asset. However, the research team found that vegetation management benefits vegetation, safety features, and structural assets.

Several states reported that RVAM work is completed reactively (i.e., in response to vegetation growth, complaints, and service requests). Three chief complaints or service requests that state DOTs receive are about the appearance of the right-of-way, sight distance issues, and inspectors being unable to complete structural surveys because of vegetation blocking access. When state DOTs proactively complete roadside vegetation asset management, these DOTs mitigate complaints. By planning and scheduling vegetation management, state DOT staff can respond to public inquiries with the timing of planned management. State DOTs can further mitigate complaints by using public information campaigns to set expectations about maintenance goals. Proactive management means staff experience fewer issues obtaining the correct equipment; however, reactive management creates issues where the equipment needed is outside the local management unit and being used by another team or is in the shop for repairs or maintenance. Proactive management reduces incidents of customer complaints as well as issues with inspectors being unable to survey structural assets (e.g., bridges and culverts) successfully. State DOTs using BIM or 3D mapping to design and map their ROW can manage the ROW proactively because they are aware of where the vegetation assets and roadside safety features are. Proactive management allows for vegetation and roadside safety feature assets to be replaced during or directly after construction, which, in turn, can reduce the amount of work completed reactively and allow state DOT staff to maintain a schedule and ensure proper equipment and staff are available when needed.

When vegetation is not present along the roadway, slope failures and other erosion issues can occur. Vegetation failures can affect the right-of-way structural elements (e.g., pavement and guardrails). Twelve targeted survey respondents (75%) use herbicide to create bare ground; one of the case study state DOTs has explicitly removed specifications calling for bare ground under guardrails because bare ground can be detrimental to guardrail and cable rail post stabilization. (This is because bare ground contributes to erosion, and the ground beneath the guardrails and cable rails would wash away, especially after heavy precipitation.) Slope failure can cause issues for state DOTs by reducing structural stability and can harm motorists and state DOT staff on the roadway through landslides and rockslides. Some state DOTs carefully manage slope

failure, with states (e.g., California) deploying drones to review damage from wildfires and other natural disasters to reduce the effect of impending slope failure or to prevent slope failure from occurring.

State DOTs can prevent vegetation from growing directly in front of safety features along the roadside. When vegetation overtakes safety features (e.g., guardrails), motorists using the roadside cannot see them and can hit them, thinking the area is a safe location to exit the roadway in an emergency. Occasionally, the vegetation, especially sturdier vegetation such as trees, can prevent the structure from operating correctly. Finally, vegetation growing over structures such as sound walls or a bridgeʼs supporting wall, can affect the assetʼs structural integrity. Vegetation management via plant growth regulators, mowing, string trimming, and other methods is necessary.

3.7 Beneficial Vegetation Impacts on the Right-of-way

Vegetation assets can enhance roadside maintenance activities, structural asset use, and driversʼ temperaments. Proactively managed vegetation assets and roadside safety features can foster a safe, reliable roadway system for the traveling public while saving the state DOT money through reduced management activities.

Beneficial Effects on Surrounding Environment

Vegetation affects the surrounding environment in multiple ways. How vegetation benefits the roadside varies based on the climate and growing conditions. One way to help ensure structural asset integrity is to ensure that the vegetation surrounding the structural asset is maintained. Well-maintained vegetation assets can increase the lifespan of adjacent or related structural assets (e.g., increased infiltration prevents erosion, water damage, and flooding on the roadway), and provide fire-resistant ground. Examples of how vegetation can benefit the roadside environment include the following:

• Appropriate choice of vegetation is essential. For example, vegetation known to survive or germinate quickly after wildfires can help prevent erosion and landslides after large-scale wildfires along hills and mountains. Conversely, cheatgrass (Bromus tectorum) is an example of an invasive plant species that grows more readily in areas prone to wildfires. It is highly flammable and increases the intensity (temperature) and frequency of wildfires (Colorado State University Extension 2012).
• Keeping vegetation mowed (e.g., grass) can act as a firebreak in fire-prone regions of the United States.
• Installing native vegetation, especially generalist and/or vigorous species, can reduce the pressure of invasive plant species along the right-of-way. For example, in locations where it is native, little bluestem (Schizachyrium scoparium) establishes well along the right-of-way and provides protection from erosion and encroachment by invasive plant species. Each state DOT should use plant species appropriate to the region.
• Establishing appropriate vegetation can ensure that there is sufficient coverage to prevent erosion.
• Installing pollinator habitat can provide resources for pollinators, including T&E pollinator species.
• Installing wildlife corridors ensures that wildlife have access to habitat while reducing their effect on drivers and increasing the safety of travelers.
• Increased infiltration from areas seeded with native plants with deep roots reduces issues with flooding and thus water damage issues with structural assets (e.g., buckling pavement or erosion).

Reduction of Structural Asset Use

Vegetation assets, including roadside vegetation safety features, can reduce the number of structural assets along the right-of-way. A state DOT should only use vegetation as a replacement for structural assets with the approval of an engineer. Examples of how vegetation can be used to reduce the need for structural assets include the following:

• A state DOT can install living snow fences instead of wooden panels or plastic snow fencing. A living snow fence provides the same benefits as structural fencing with the added benefit of providing pollinator/wildlife habitat to birds and other small animals.
• The use of trees and shrubs, where appropriate, instead of sound walls, provides a visual barrier and improved appearance for the traveling public.
• The use of appropriate vegetation within ditches can reduce the use of riprap or concrete. The vegetation will increase infiltration and reduce flash flooding.

Driver Temperament

During commutes, drivers can be on the roadway for significant portions of their day. The view from the vehicle, particularly during heavy traffic events (e.g., rush hour) can increase anxiety and blood pressure and impair mood (Jiang et al. 2021). Examples of how driver temperament can be affected include the following:

• Replacing some sound walls with trees and shrubs will increase the amount of vegetation a person sees during their daily commute, particularly in cities.
• Installing pollinator habitats along rest stops and other areas of the right-of-way enhances the public view and perception of the right-of-way when accompanied by informational signage at rest stops.