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Chapter 9
Roadside Vegetation Management
9.5. Planning for Invasives Control

Once DOT maintenance staff know what they are dealing with on the roadside, they can more easily identify priorities in addressing target species. Such priorities may be determined through a risk assessment, after which action plans may be developed. After locating and recording undesirable vegetation on a map, prioritizing sites, and making a realistic assessment of resources to address invasives, a DOT can more readily develop plans, policies, and standards to execute the work.

As of 2005, about a third of DOTs were linking identified locations of invasive species infestation to treatment plans. This occurs in a variety of ways, from highly informal to formal plans. Florida DOT is identifying locations of its two, top priority invasive species for treatment planning. At Arkansas Highways, maintenance area personnel identify Johnson grass (Sorghum halepense) for spot control efforts in the course of their other work. Kansas DOT also identifies locations for spot treatment, on a limited basis. MoDOT tracks and treats sites at the district level. Nevada DOT tracks infestations in stormwater drainage basins and wetland mitigation sites only. At WisDOT, District maintenance supervisors work with the county maintenance patrolmen who are familiar with locations to develop the annual treatment program, based on county personnel knowledge and experience rather than mapping. In general these informal systems are handled by DOT regions, districts, or maintenance shops.

Continuous improvement can be accomplished through a variety of means. An EMS encourages a cycle of goal-setting (PLAN), implementing actions (DO), and re-evaluation (CHECK and ACT) to achieve continuous improvement with regard to environmental objectives. While an Environmental Management System (EMS) or EMS-style Integrated Vegetation Management (IVM) program explicitly seeks to evaluate procedures, strategies, and implementation for continuous improvement, DOTs use other mechanisms as well. TxDOT is among those DOTs that are documenting all treatment procedures, but still working on including feedback and effectiveness information. The statewide consistent pesticide application recordkeeping system that Mn/DOT and the University of Minnesota are developing for pesticide use and target species/situations (Canada thistle, Cirsium arvense, guardrails, etc.) is expected to provide data for decision support for continuous improvement, as well. The Adirondack Park Invasive Plant Program and WSDOT have information management and decision support components of their system, as treatment areas are tracked and effectiveness information is gathered.

About a quarter of DOTs (2005 survey) revise treatment plans, reallocate resources if necessary, and develop systems to document treatment and continually improve effectiveness. An EMS can help agencies document effectiveness and make the case for additional resources. Since WYDOT contracts invasive species control out to the state Department of Agriculture, the state Maintenance Engineer receives annual reports showing treated areas, cost overruns and underruns, and percentage of right of ways reviewed. They also indicate any problems that were encountered in the program for that year. If there are issues or concerns they are discussed and addressed with the WDOA. WDOA will reallocate statewide funding for the WYDOT noxious weed program if needed. Other states may modify allocations based on district feedback (MoDOT) or on a district by district or district maintenance area basis (Mn/DOT). Greater flexibility for reallocation is available with a statewide program, with centrally responsible personnel and dedicated funding specifically for control of invasive species.(Arkansas Highways) In some cases, treatment procedures may be refined on a central level, with reallocation of resources continuing on the district level (TxDOT). Oregon DOT indicates that the department tries to direct any remaining maintenance dollars at the end of budget bienniums to supplemental herbicide purchases.


9.5.1 Integrated Roadside Vegetation Management (IRVM)
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Integrated Vegetation Management (IVM) or the Integrated Roadside Vegetation Management (IRVM) approach encourages stable self-sustaining vegetation with limited use of mowing and herbicides. IRVM starts with good soils management, planting design, and revegetation, and then recognizes proper mowing or restrictions, weeding, pruning, and thinning. Herbicide use is not ruled out, but other strategies are combined to limit its necessity. As IRVM strategies take hold over time, mature roadside plant environments lead to long-term herbicide use reductions and minimal of maintenance requirements.

According to the upcoming NCHRP 20-5, 33-04 on IRVM, on average, 58 percent of DOTs' newly planted acreage requires no significant maintenance work on a perpetual basis; 23 percent indicted that less than 20 percent of the newly planted acreage requires significant maintenance work on a perpetual basis. Around a quarter of responding state DOTs were aiming for 90 to 100 percent of planted acreage requiring no significant maintenance work on a perpetual basis. [N]

Iowa DOT was an early leader in the implementation of IRVM, which the agency understood as simply using the most cost-effective and ecologically-sound method of management on a site by site basis. The approach was based on the following principles. [N]

  • Nature does not allow bare soils to exist.
  • Bare soils are revegetated by successions of plant groups until a most-fit community of plants develops.
  • Disturbance of the vegetative cover reverses the succession of revegetation back to the bare soil starting point, and therefore allows more invasions.

The emphasis on weed eradication rather than weed prevention has led to increased mapping of vegetation, statewide planning, and new maintenance/construction practices.

Within IVM, various key elements of IPM systems have only recently been developed or recognized; some examples include: [N] [N]

  • Managing a pest with integrated control measures, including prevention and an emphasis on biological control (liken to the use of low-growing plant communities to naturally control pest tree populations).
  • Growing emphasis on monitoring and assessment (including refined efforts to document a pest problem).
  • Decisions based on tolerance levels (of pest species/noxious weeds).
  • Professional-grade prescriptions of treatments.
  • Formalized efforts to determine long-term efficacy and effectiveness of treatments.


9.5.2 Developing IVM or IRVM Plans
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The IVM plan identifies environmental constraints and gives the vegetation manager flexibility in management methods. Properly executing integrated vegetation management practices using a combination of methods can result in the conversion of rights-of-way to a plant community requiring minimal maintenance activities in the future. Integrated vegetation management balances service reliability, environmental compliance, and customer service while lowering the cost of maintenance over time. [N] Working with utility communities and now NYSDOT, Nowak and Ballard of the State University of New York call IVM "a sophisticated system of information gathering, planning, implementing, reviewing, and improving vegetation management treatments," which "differs from past management approaches to managing vegetation on ROWs in its greater breadth and complexity of management considerations, and in its higher level of sophistication and effort in evaluating management choices." [N] As a continuous cycle of information gathering, planning, implementing, reviewing, and improving vegetation management treatments and the related actions, IVM constitutes an Environmental Management System for roadside vegetation. An overview of common IRVM or IVM steps are included with the Appendices in Chapter 11. Model DOT IVM or IRVM planning efforts are described in this section.


Iowa DOT defines IRVM as a long term approach to vegetation management that: [N]

  • Systematically evaluates each area to be managed.
  • Determines which plant communities best fit the area.
  • Develops procedures that will encourage, enhance, or reestablish desirable plant communities.
  • Provides self-sustaining, diversified, visually interesting vegetation.
  • Keeps safety and an improved environment as priorities.
  • Utilizes the most beneficial methods to prevent or correct undesirable situations caused by disturbance or less than optimum vegetative ground cover.

Iowa DOT's IRVM plan is brief and general, allowing adaptation by counties. Iowa DOT defines the prime purpose of roadside vegetation as holding soil in place without creating hazards. At the same time, Iowa DOT hopes to address other desirable uses for roadside vegetation (aesthetic, economic, and environmental) once safety and functional requirements are met. The goals of Iowa DOT's Integrated Roadside Management Plan are to:

  • Preserve and provide safe, functional and environmentally improved corridors of travel throughout the state.
  • Utilize a long-term integrated management program that promotes desirable self-sustaining plant communities. Encourage those plant communities that are native to Iowa through preservation and re-establishment whenever practical.
  • Bring about considerable reduction and possible elimination of the use of chemicals as a control method of undesirable plants.
  • Enhance the scenic qualities of the roadsides and their value as wildlife habitat.

To achieve these goals, Iowa DOT outlines the following procedures, which follow a Plan-Do-Check-Act (EMS-type) process as follows:

  • Inventory the sites to be managed.
  • List the existing areas of desirable vegetation as well as those that need improvement.
  • Determine the appropriate management methods needed.
  • Determine the best time to implement management procedures and see that they are accomplished at that time. Temporary procedures may be needed to preserve an area before permanent procedures can be utilized.
  • Evaluate the results periodically.
  • Take further measures if necessary.

Iowa DOT and the Iowa State Legislature have supported establishment of an Integrated Roadside Vegetation Management center at the University of Northern Iowa, which has produced resources of value to multiple state DOTs.

Mn/DOT Process for IRVM Planning

Mn/DOT's process for IRVM planning is detailed in the Minnesota Best Practices on Roadside Vegetation Management and summarized below. [N]

Preliminary Planning, Categorization and Goals

  • A local plan adapted to fit local culture, political concerns, and climate and environmental conditions is best . Each roadway is unique, and one plan for all roads in a jurisdiction may not be appropriate. The next step in moving towards integrated roadside vegetation management is to evaluate the roadways for which an agency is responsible, and assign them to categories for which a plan can be developed.
  • Plan development should be a team effort , with input from those people having expertise in landscape architecture, maintenance, design, construction, biology, horticulture, utilities, and public relations as well as from general citizens. A steering committee responsible for developing the plan, providing guidance on how it is run, and reviewing the annual work plan and progress may also be created.
    • Prior to plan development, the agency should identify the roadways they are responsible for maintaining and prioritize them according to the level of management they will receive. The amount and type of vegetative maintenance done on each roadside will depend on the category to which it is assigned, whether urban or rural, or based on zoning, traffic volumes, or roadway type.
    • While developing the plan and considering maintenance strategies, keep the following guidelines in mind: 1) timing is an important factor for all control and maintenance methods; 2) programs should be kept flexible to allow for changes as needed; 3) a combination of several control methods is usually more effective than any single treatment; and 4) maintenance costs are lowest when programs are planned and carried out on schedule.
  • Identify the desired outcome for a given feature . For example, is the objective to have low maintenance, return the roadside to prairie grasses, maintain golf course-like sod, or re-establish a wetland? Once the desired outcome has been identified, a plan can be developed to achieve it.

Assessing Existing Conditions

Assess existing conditions to assign and prioritize management strategies for an area. Soil, topography and vegetation will steer management techniques:

  • Soil. Understanding the type of soils present and their physical characteristics is important when outlining a plan for roadside vegetation management. Soil type and texture determine vegetation selection, herbicide application rates, fertilization needs, and erosion potential. Once known, management techniques should be targeted to those conditions. The ideal surface soil is composed of 5 percent organic matter, 25 percent air, 45 percent mineral material, and 25 percent water. The organic material provides fertility and water-holding capacity and supports microbial life. Oxygen is required for all root growth. Along roadsides, soil is typically stripped of its nutrients and compacted such that little air remains in the soil, leaving a very hostile environment for vegetation to flourish. When trouble-shooting to determine causes of vegetation problems, assessing the soils in an area, especially for excess nitrogen, may explain excessive weed growth or resistance to chemical control methods.
  • Soil Health . Healthy soil is a critical element for establishing a healthy roadside environment. Even the most appropriate and useful tools for managing roadside vegetation may not work if the soil lacks enough nutrients to support the targeted vegetation. To improve unhealthy soil, try measures such as the use of a fertilizer, compost, aeration, or deep scarification to incorporate oxygen into the soil. If improving soil health is not possible, choose appropriate vegetation (that does not need high nutrient soils to flourish) for establishment in that area. One way to assess the health of the soil is to send a sample to the the state Extension Service Office. For a small fee, the service will analyze the nutrient content of the soil sample and recommend the appropriate type and application rate for any necessary fertilizer.
  • Soil Considerations for Herbicide Use . Use lower application rates for coarse-grained soils and higher rates for fine-grained soils or soils high in organic material. Learn the potential for herbicide runoff before using it. Do not spray in steep slope areas if rain is likely since steeper slopes increase runoff.
  • Native Vegetation . There are three main reasons for preserving native plants:
    • Environmental: There are no substitutes for the original wild species of your state. Once lost, their genetic material can never be re-created. Also, native wildlife often depends on native vegetation for survival.
    • Economic: Native plant communities are relatively stable and require little maintenance. Natural communities provide good erosion control and are less susceptible to weed invasions.
    • Aesthetic: Native wildflowers and grasses provide seasonal color changes along roadsides, a natural beautification. They also screen undesirable views and objects if planted strategically.

Developing a Plan

After the steering committee or appropriate personnel have been assembled and roadside areas have been categorized, Mn/DOT suggests that an IRVM Plan be written, following the steps below: [N]

  1. Develop a vision or mission statement. A vision statement is a picture of your road 10 to 20 years in the future. It includes your highest aspirations for what the roadside can become and serves as a source of motivation for all those involved in the process. A mission statement is broad and outlines the ultimate reason for the program's existence.
  2. Collect pertinent data, such as costs, vegetation (existing and desired), available personnel, and resources. This step includes reviewing records of current maintenance operations and taking an inventory of current roadside vegetation conditions.
  3. Establish goals and objectives. When doing so, consider the following basic principles:
    • Safety for the traveling public and maintenance staff
    • Maintenance of the infrastructure and highway integrity
    • Cost-effective use of public resources
    • Environmentally sound decision-making
    • Needs and concerns of adjacent landowners and the traveling public
  4. Analyze and prioritize goals and objectives. Identify which goals are most important. This allows problem areas to be dealt with first, making other goals and objectives easier to reach.
  5. Assign duties and responsibilities for each program participant. With input from those staff members who will be responsible for plan implementation, assign duties and responsibilities.
  6. Plan for budget considerations. Identify costs connected with implementing each plan element, as well as ways to deal with budget constraints. This may include planning for equipment purchases and staff needs and increasing the efficiency of existing operations.
  7. Provide an opportunity for research and innovation. Note research opportunities that may result in innovations for improving quality, reducing costs, and improving working conditions for maintenance staff.
  8. Provide evaluation criteria. This may be the most important element of the IRVM plan. It is critical that some benchmark be developed to measure program success. Meet and document short-term goals and objectives. Maintain records of implementation activities over time to evaluate overall direction and accomplishments. Periodically evaluate the plan to determine if it is advancing and if it has reasonable and attainable goals and objectives. Make changes as needed.

Implementing the Plan

Mn/DOT recommends the following steps to implement the IRVM plan: [N]

  1. Identify appropriate methods and application for control. For each maintenance activity, identify the appropriate control method. This could include mechanical methods, such as mowing and aeration; biological or natural processes; cultural methods, such as appropriate seed selection, planting and mulching, or burning; chemical methods, such as the use of herbicides and pesticides; a hands-off approach; or preservation and conservation.
  2. Train. Train all staff responsible for implementing each element of the IRVM Plan regarding the plan components and their responsibilities. This is especially important for those staff members who will be completing the actual maintenance activities.
  3. Keep records. Keep records of maintenance activities. This includes information about the type of control used, conditions under which it was applied, and general management information. Information about the control method includes weather, application area limits, time of application, concentration and quantity of any chemicals applied, and other information as needed. For general management purposes, hours, personnel, equipment, and costs are needed to set priorities, evaluate cost-effectiveness, and budget time and money for future activities. A complete and continuously updated location map, indicating control activities and dates of application, is recommended. This can be integrated with a Geographic Information System (GIS) to automate the record-keeping process.
  4. Evaluate the program. Regularly evaluate in order to measure the success of an IRVM Plan. This may include tracking the number of citizen complaints received before and after plan implementation, cost reductions for certain maintenance activities, and allocation of staff time. Evaluate the effectiveness and success of plan elements and make changes as necessary. Evaluation is an ongoing process, as are changes and improvements.

New York State's 6-Step Approach to IVM Planning and Implementation

Integrated Vegetation Management (IVM) has been used on powerline corridors for over 20 years in New York State, where a focus on culturing desirable plant communities that minimize the presence of undesirable plants has reduced treatment needs, and reduced herbicide usage by over half during that period. [N] Nowak and Ballard's work with the utility industry and NYSDOT has involved a six-step approach to IVM that provides a framework for communicating, organizing, and conducting an IVM program. [N] The following step-wise system is summarized and adapted from Nowak and Ballard's work for the utility industry and EPA. [N] It closely parallels that of the Integrated Pest Management Practitioners Association, described earlier.

Step 1: Understand pest and ecosystem dynamics.

A first step to conducting IVM is to develop a working knowledge of the organisms in the managed system and how they interact with each other and the environment, with or without vegetation management, to produce ecosystem conditions. It is important to identify and understand:

  • Species life histories (reproduction, growth and longevity), plant strategies, and responses to disturbance.
  • Plant succession, changes in distribution and abundance of plants through time and space.
  • How plants and communities can be manipulated to control the rate and direction of plant succession via interference, grazing, and other mechanisms.

Step 2: Set management objectives and tolerance levels.

Tolerance levels are specific descriptions of vegetation condition - individual plant and plant community size, abundance, and composition - that, if exceeded, trigger a need to intervene. Undesirable species are not treated unless they exceed the critical threshold. Well-defined thresholds are a critical element of IVM [N] [N] that can be useful in communicating management needs to various stakeholders, e.g., thresholds and tolerance levels can be used to demonstrate the cyclic nature of vegetation dynamics, which supports a need to control vegetation on a regular basis. Stakeholders include vegetation management professionals responsible for management decisions on a particular ROW, landowners of the ROW or adjacent properties, governmental regulators responsible for administering State and Federal policies and laws, and non-governmental organizations with a general concern for the environment.

Step 3: Compile treatment options.

Different treatment options may be needed to match variable environmental and site conditions, concerns and interests on a ROW. Vegetation treatments can be grouped into categories, such as: mechanical, chemical, cultural, physical, biological, and ecological; however, IVM does focus on integrating biological/ecological control into all treatment schemes. Creation of stable, low-growing plant communities is the long-term objective, and biological/ecological control produces a long-term reduction in treatment efforts, and a reduction in herbicide use. [N] [N]

Step 4: Account for economic and environmental effects of treatments.

Economic and environmental considerations factor into choice of treatment. Cost effectiveness may be used as a measure of the success of a treatment in terms of economics, plant community dynamics, and related environmental considerations; [N] [N] direct costs include labor, equipment, and materials to treat ROW vegetation, while indirect costs include the loss of values or service that can result from a treatment. The latter are often associated with water quality, pollution, wildlife habitat, and aesthetics, or other ways that the environment can be degraded. Effectiveness pertains to production of desired vegetation conditions and associated benefits and values with operation and management of the transportation corridor in the public interest, taking environmental interests and values into account. Cost effectiveness timeframes may be short- or long-term, and often, efforts must be made to balance short-term savings with long-term costs. For example, it may be monetarily less costly to mow a ROW today vs. use of herbicides, but mowing may produce higher costs over the long-term because of short-term control of vegetation conditions and shorter treatment cycles than can be achieved with other treatments. [N] [N] IVM is used to maximize cost effectiveness of management efforts, minimizing costs while creating the desired vegetation conditions and associated positive values associated with these conditions over the long-term.

Step 5: Develop site-specific treatment plans.

After developing a suite of treatment options (Steps 2, 3 and 4), and weighing the effects of those treatments on long-term production of vegetation conditions and associated benefits and values, a treatment is chosen by the professional vegetation manager. Prescriptions should not be written for whole ROWs, but are instead developed for specific sections of any one ROW and the constraints therein. It is important to base treatment choices on inventory and analysis of existing site and vegetation conditions, [N] particularly because these data will be critical in monitoring outcomes of treatments, as outlined in Step 6. Prescriptions for different areas and circumstances of vegetation management should include:

  • Desired future conditions of the ROW area to be treated
  • Description of the treatment as a function of current vegetation conditions, and justification of treatments, considering ecological, socioeconomic, and administrative or fiscal factors. [N] [N] Treatment recommendations are the crucial part of the prescription.

Step 6: Monitor outcomes and revise and adapt management plans.

Adaptive management incorporates learning from experience. [N] Monitoring of the effects and performance of various treatments may include:

  • Amount of materials used in treatment
  • Treatment costs
  • Vegetation conditions before and after treatment (e.g. quantification of changes in noxious weed cover)

In addition to vegetative community changes, herbicide residuals with chemical treatments, water quality, and wildlife populations can also be monitored and feed into the next round of treatment planning and decisionmaking. Vegetation conditions are compared to the desired condition set during the "Management objectives and tolerance levels" step (Step 2), and described in prescriptions during the "Site-specific implementation of treatments" step (Step 5). Any disparities between "desired" and "achieved" results are investigated, and future treatment options adjusted accordingly. Monitoring assures that treatment effects are gauged, and shortfalls corrected by improving management schemes to better accomplish management objectives.

To What Extent Are You Implementing IVM: A Self- Evaluation

Nowak and Ballard pose a series of questions, which maintenance managers may use to self-evaluate their current approach to vegetation management, and identify gaps between current systems and the integrated approach presented above. Numbers correspond to the steps presented previously. [N]

1) Do you have a detailed, basic knowledge of the managed ecosystems?

2a) Do you actively involve stakeholders in vegetation management decisions?

2b) Do you consider tolerance levels when determining the need to treat vegetation (positive approach), or do you take a rote approach and treat vegetation only routinely (negative approach)?

2c) Are you proactive in vegetation management (e.g., treat vegetation in concert with tolerance levels, with decisions based on inventory and planning), or reactive (e.g., "hot spotting", where vegetation is treated after thresholds are soon-to-be, or already, exceeded)

3a) Do you maintain a broad range of vegetation treatments--mechanical, chemical, cultural, and biological--in your "toolbox", and apply a variety of treatments depending on the site and vegetation conditions?

3b) Do you foster the use of biological/ecological controls to prevent pest populations from building past economic thresholds?

4) Do you use broad considerations of cost effectiveness in selecting a treatment for a specific site?

5) Do you prescribe treatments in a site-specific manner, based on a contemporary inventory of ROW resources?

6) Do you monitor the results of treatments to compare actual conditions vs. desired future conditions, and look to improve the system based on that comparison?

In 2003, NYSDOT developed a 10-point invasive transportation vegetation management plan, consisting of the following components: 1) Developing a prioritized list of threatening flora or fauna based upon regional environments, 2) Field and GIS mapping of existing invasive populations, 3) Integration of invasive species identification and analysis as part of the department's normal NEPA /SEQR processing, 4) Evaluation of potential impacts caused by construction or maintenance activities, 5) Development of preventive best management practices, 6) Testing, execution and evaluation of eradication measures, 7) Annual reviews and updates of the vegetation management plans, 8) Progression of innovative design solutions to reduce the opportunities for the introduction or spread of invasive species, 9) Promote a climate of interagency cooperation and sharing of coordinated research with public and private sectors, 10) Increase employee and public knowledge through outreach training of the effects of invasive species to the users. [N]

NYSDOT's Draft "Metric for Assessing Performance of Integrated Vegetation Management on Rights-of-Way"

As part of NYSDOT's evaluation of their current vegetation management program and the agency's "Alternatives to Herbicide" program, NYSDOT is developing a systematic framework and research protocol for identification, evaluation, and implementation of environmentally sensitive, lower maintenance, and cost effective vegetation management techniques that can be integrated into the overall vegetation management program. [N] To assist NYSDOT in this effort the State University of New York (SUNY) developed a Draft "Metric for Assessing Performance of Integrated Vegetation Management on Rights-of-Way," which is listed in the Appendix of this document. [N] Assessments include interdisciplinary field meetings and interviews with staff; visits to a representative sample of roadsides; and review of standard operating practices, vegetation conditions, field performances, site challenges, and vegetation management innovations. A report is developed that presents findings and recommendations associated with each principle and criteria. Each principle will have highlighted strengths and weaknesses, and sets of commendations for successes and recommendations for program improvement.


9.5.3 Resources for Integrated Vegetation Management Planning
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Appendix resources contained in Chapter 11 include detailed information on Integrated Vegetation Management Planning. The interagency gateway to invasive species control programs and tools, on the web, has a list of management plans that have been developed in each state and by each species. Decision support tools are also available. Readers can reach each of these sites at

Other resources for IVM planning include:


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Continue to Section 9.6 »
Table of Contents
Chapter 9
Roadside Vegetation Management
9.0 Introduction
9.1 Inventory of and Management for Rare Species and Sensitive Resources in the ROW
9.2 Growing Threats Drive Expansion of DOT Invasive Species Practice
9.3 Practices for Prevention of Roadside Infestations
9.4 Statewide Inventory of Invasive or Noxious Species in the ROW and Update of Databases
9.5 Planning for Invasives Control
9.6 Roadside Vegetation Control Methods and Resources
9.7 Management of Visual Quality of the Roadside
9.8 Staffing, Training, & Partnerships
Lists: Examples | Tables | Figures
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