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40 CHAPTER 3. STATE TRANSPORTATION AGENCY PRACTICES One of the objectives of NCHRP 14-41, Long-Term Vegetation Management Strategies for Roadsides and Roadside Appurtenances, is to collect information on current practices used by DOTs, institutional obstacles, and the concerns that state agencies have regarding VMS treatments. This chapter summarizes DOTsâ use of non-herbicide, long-term VMSs that are designed to prevent or significantly retard the growth of unwanted vegetation around roadside appurtenances and along roadsides. This chapter includes the survey of practice sent to all DOTs, follow-up interviews with select DOTs, and information regarding state DOT documents for VMS treatments. Researchers identified additional methods and technologies that DOTs are piloting, additional guidance required, and how DOTs would use the findings from this research. SURVEY OF PRACTICE The NCHRP 14-41 web-based survey and interview process were designed to optimize responses by balancing the length and level of detail requested of the respondents. The draft survey and interview questionnaire were reviewed by the Institutional Review Board for Human Subject Protocols for compliance and sent to the NCHRP panel for approval prior to deployment. The original project title was Permanent Vegetation Control Treatments for Roadsides, using the acronym PVC. Over the course of the project, the title was revised to Long-Term Vegetation Management Strategies for Roadsides and Roadside Appurtenances, using the acronym VMS. There was confusion over the use of the acronym PVC, and it was determined that long-term was a more accurate descriptor than permanent for the materials presented. The original survey retains the original title and acronym use. However, the survey results show VMS as the acronym. An email invitation to participate in the web-based survey was sent to the maintenance directors at all state DOTs. The research team sent two reminder emails to non-responding agencies requesting completion of the survey by the requested date. The objectives of the survey were the following: ⢠Gather information on current practices, institutional obstacles, and the concerns that DOTs have regarding VMS treatments ⢠Gather information on the selection process implemented by DOTs ⢠Identify any missing applications that require further guidance (e.g., controls for use with cable barriers) ⢠Identify any innovative methods or technologies that DOTs have experimented with ⢠Gather information on any additional guidance that is required Seventeen states responded to the survey, with some states giving multiple responses based on regional differences. Respondents included vegetation managers, maintenance engineers, roadside environment managers, and other staff responsible for designing and maintaining roadsides. This chapter highlights the key findings of the survey. Figure 29 illustrates the U.S. map showing the DOTs that responded to the survey. Table 6 lists the respondents.
41 Figure 29. Survey Responses by State. Table 6. State DOT Survey Respondents. State Title Agency/Organization AR State maintenance engineer Arkansas Department of Transportation AZ Roadside resource specialist Arizona Department of Transportation CA Senior landscape architect California Department of Transportation CT N/A Connecticut Department of Transportation ID Roadside program manager Idaho Transportation Department IN Roadside maintenance specialist Indiana Department of Transportation KS Bureau chief of maintenance Kansas Department of Transportation KY Roadside environment state administrator Kentucky Transportation Cabinet ND State maintenance engineer North Dakota Department of Transportation NV Chief maintenance and asset management engineer Nevada Department of Transportation RI State highway maintenance operations engineer Rhode Island Department of Transportation SC Vegetation manager South Carolina Department of Transportation TN Transportation manager 2 Tennessee Department of Transportation TX Director of maintenance TxDOT VT Stormwater tech Vermont Agency of Transportation VA State roadside vegetation manager Virginia Department of Transportation WV Assistant director of Maintenance Division West Virginia Department of Transportation/ Division of Highways
42 The survey contained multiple questions related to vegetation control treatments, such as current state practices, institutional obstacles, and the concerns that agencies have regarding VMS treatments. Table 7 lists the questions used for this survey. Table 7. Survey Questions. Question Number Survey Question 1 Survey introduction and instructions. 2 Contact information (name, agency, location, area of responsibility, state, title, address, and phone number). 3 Does your agency currently use non-herbicide PVC for preventing or significantly retarding the growth of unwanted vegetation around roadside appurtenances and along roadsides? 4 Does your agency have a published/established protocol for using non-herbicide PVC? 5 If yes, please provide the most current document and/or a website link in the text box below. If the document is not publicly available through your agencyâs website (i.e., internal to the agency), please submit the document via email at PVC@tti.tamu.edu. 6 If your agency does not have an established protocol, please provide any details of non- herbicide PVC methods or practices currently underway within your agency or region in the space below or in a return email at PVC@tti.tamu.edu. 7 Has your agency collected data or performed research regarding any of the following worker safety aspects of the performance of non-herbicide PVC? Please select all that apply. (Choices: installation, maintenance). 8 Has your agency collected data or performed research regarding any of the following cost aspects of the performance of non-herbicide PVC? Please select all that apply. (Choices: installation, maintenance, direct labor, materials, equipment, management/planning). 9 Has your agency collected data or performed research regarding any of the following material performance aspects of the performance of non-herbicide PVC? Please select all that apply. (Choices: material integrity, longevity, ease of installation, retrofit capabilities, maintenance, impacts of mowing, impacts of ice/snow, impacts of storm water runoff, effectiveness). 10 Has your agency collected data or performed research regarding any additional aspects of the performance of non-herbicide PVC? If yes, please describe. 11 If you selected any of the performance aspect options above, please provide the most current document and/or a website link. 12 If you have PVC performance data that is NOT compiled in a formal document, please supply. 13 In what locations does your agency use non-herbicide PVC? Please select all that apply. (Choices: guardrails, median barrier systems, edge of pavement, gore areas, embankments, other [please specify]) Question 13: In what locations does your agency use non-herbicide PVC? Please select all that apply. Other (please specify). Narration. 14 If you selected any of the options above, please provide the most current document and/or a website link. If the document is not publicly available through your agencyâs website (i.e., internal to the agency), please submit the document via email at PVC@tti.tamu.edu. 15 If your agency does not have an established protocol, please provide details of PVC implementation in the space provided or in a return email at PVC@tti.tamu.edu.
43 Question Number Survey Question 16 What types of non-herbicide PVC does your agency currently use? (Choices: minor concrete pavement, standard concrete pavement, asphalt concrete pavement, rock blanket, gravel mulch, weed control mat [fiber], irrigated/ornamental vegetation, native and non- irrigated vegetation, rubber weed mat, organic mulch, asphalt composite, other [please specify]) Question 16: What types of non-herbicide PVC does your agency currently use? Other (please specify). Narration. 17 If applicable, please provide information regarding other types of PVC usage. 18 If your agency no longer uses a specific non-herbicide PVC, please provide details regarding performance and/or reason for discontinuing use in the space below or in a return email at PVC@tti.tamu.edu. 19 What selection criteria does your agency use regarding the type of non-herbicide PVC specified? Select all that apply. (Choices: roadway context, e.g., urban, suburban, rural; aesthetics; other [please specify]) Question 19: What selection criteria does your agency use regarding the type of non- herbicide PVC specified? Select all that apply. Other (please specify). Narration. 20 Please provide details below regarding information your agency considers important for inclusion in a guidance tool for selecting appropriate non-herbicide PVC or in an email at PVC@tti.tamu.edu. 21 May we contact you for a follow-up mail and/or telephone interview? PRACTITIONER SURVEY RESULTS The survey responses are listed in the following tables. The focus is on DOTsâ use of non- herbicide VMSs for preventing or significantly retarding the growth of unwanted vegetation around roadside appurtenances and along roadsides. Table 8 shows results for Questions 3 and 4. Table 8. Responses for Survey Questions 3 and 4. Question Number âYesâ Response âNoâ Response or Skipped Question 3 AR, AZ, CA, ID, NV, ND, RI, TX CT, IN, KS, KY, SC, TN, VT, VA, WV 4 AR, AZ, CA, TX CT, ID, IN, KS, KY, NV, ND, RI, SC, TN, VT, VA, WV Note: CT and KY answered ânoâ to Questions 3 and 4; however, they submitted replies to the subsequent survey questions. Arkansas, California, North Dakota, Nevada, and Texas supplied documents/website links to their VMS documents in response to Question 5, as shown in Table 9.
44 Table 9. Responses for Survey Question 5. State âYesâ Response AR Arkansas State Highway and Transportation Department (ARDOT) Standard Specifications of Highway Construction 2014 edition https://www.arkansashighways.com/standard_spec/2014/2014SpecBook.pdf CA Caltrans Roadside Management Toolbox www.dot.ca.gov/design/lap/landscape-design/roadside-toolbox/index.html www.dot.ca.gov/design/lap/landscape-design/research/weed-and-pest-research.html ND The only area we are doing this is using asphalt under guardrail. NV We do not have protocols for using non-herbicide VMSs, but it is the policy of the State of Nevada that landscape and aesthetics will be considered along with all other design factors in all transportation projects throughout their life cycles. Please see the link for more information. https://www.nevadadot.com/projects-programs/landscape-aesthetics TX Metal Beam Guard Fence (Mow Strip) MBGF(MS)-19 https://www.dot.state.tx.us/insdtdot/orgchart/cmd/cserve/standard/rdwylse.htm#BARRIER(ST EEL) Question 6 requested information regarding non-herbicide VMS methods or practices currently underway that may not be included in a published document. Table 10 shows these responses. Most of the agencies without a published protocol reported the use of concrete, mulch, or some other kind of aggregate material. Table 10. Responses for Survey Question 6. State Response AR Aggregate material, asphalt, or concrete along wire rope safety fence mow strip, guardrail, median barrier, edge of pavement, ditch paving, and other non-vegetated areas. Filter blanket and rip rap slopes. CA We also use copious amounts of gravel mulch, wood mulch, and paving (pervious if possible) to minimize areas where unwanted vegetation can grow. There is not a statewide protocol to decide which non-herbicide VMS methods are used, but there are standard guidelines in place for this. Standards available at the link. http://ppmoe.dot.ca.gov/des/oe/construction-contract-standards.html ID We use mowing, disking, grading, rock armor, concrete surface treatments, mats, and non- irrigated native vegetation. IN We do place aggregate/millings or concrete in some cases under some infrastructure. ND The only area we are doing this is using asphalt under guardrail. NV In urban areas, we use rock mulch and decomposed granite. RI We have begun using asphalt millings under and around guardrail and other areas where vegetation growth is problematic. TX We treat guardrails in high-traffic areas with concrete. Table 11 shows the worker safety research data categories collected for Question 7. California and Connecticut have conducted research in the areas of installation and maintenance, while Texas has only conducted research concerning installation.
45 Table 11. Responses for Survey Question 7. State Worker Safety Aspect Installation Maintenance AR, ID, IN, KS, KY, ND, NV, RI, SC, TN, VA, VT, WV Not Applicable Not Applicable CA Yes Yes CT Yes Yes TX Yes No Table 12 shows the responses to the request for data regarding cost aspects of the performance of non-herbicide VMSs. The most common research conducted by DOTs is regarding material costs, with California, Connecticut, and Texas all having conducted research. Table 12. Responses for Survey Question 8. State Cost Aspect Installation Maintenance Equipment Materials Direct Labor Management/ Planning AR, ID, IN, KS, KY, ND, NV, RI, SC, TN, VA, VT, WV N/A N/A N/A N/A N/A N/A CA Yes Yes Yes Yes Yes Yes CT Yes Yes No Yes No No TX No Yes Yes Yes Yes No N/A = Not Applicable Table 13 shows the material performance aspects reported by different agencies. Table 13. Responses for Survey Question 9. State Material Performance Aspect* MI L EI R M IM ICS ISW E MIL ID, IN, KS, KY, ND, NV, SC, TN, VA, VT, WV N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A CA Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes CT No Yes No No No No No No No Yes RI Yes Yes Yes No Yes No No No Yes Yes TX Yes Yes Yes Yes Yes No No Yes No Yes * MI = material integrity, L = longevity, EI = ease of installation, R = retrofit capabilities, M = maintenance, IM = impacts of mowing, ICS = impacts of ice/snow, ISW = impacts of storm water runoff, E = effectiveness, MIL = material integrity longevity N/A = Not Applicable Table 14 shows the additional research relevant to VMSs that different agencies collected.
46 Table 14. Responses for Survey Questions 10 and 11. State Response CA Anecdotal information sharing between districts on performance. Multiple research topics. Please see the research at these locations. http://www.dot.ca.gov/design/lap/landscape-design/research/weed-and-pest-research.html http://www.dot.ca.gov/design/lap/landscape-design/roadside-toolbox/index.html NV We only collect labor, materials, and equipment usage for landscape maintenance in general. TX We tried ground rubber tires, but after installation and a few rainstorms, they all washed away. Question 12 requests the respondent provide VMS performance data that are not compiled in a formal document. Table 15 shows the responses. Table 15. Responses for Survey Question 12. State Response CA Rubber mats have limited longevity under guardrail. Minor concrete is more effective but takes considerably longer to repair after a guardrail hit. Most often, field maintenance does not repair the concrete. CT The Connecticut Department of Transportation has used both processed aggregate and bituminous on projects in the past, only below new guiderail. Based on the limited success and maintenance issues associated with those projects, the specification was revised to turf establishment, which currently is controlled with herbicides. RI It [asphalt millings] works well initially, but it does not last as long as we would like. It is not a permanent solution. Table 16 lists the locations where non-herbicide VMSs are used. All respondents using VMSs listed guardrails. Most of the respondents also use VMSs at median barrier systems and along the edge of the pavement. The other locations include signposts, gore areas, embankments, and medians. Table 16. Responses for Survey Question 13. State Location Guardrails Cable Barrier Sign Posts Edge of Pavement Gore Areas Embankments Medians Other IN, KS, SC, TN, VA, VT, WV N/A N/A N/A N/A N/A N/A N/A N/A AR Yes Yes Yes Yes Yes Yes Yes No CA Yes Yes Yes Yes Yes Yes Yes Yes CT Yes No No No No No No No ID Yes No No Yes Yes No Yes No KY Yes Yes No No No No No No ND Yes No No No No No No No NV Yes Yes No Yes No No Yes No RI Yes Yes No Yes No No No No TX Yes Yes No Yes Yes Yes No Yes California listed the other location as slope paving under structures. Texas stated VMSs are used at rest areas and travel centers.
47 Table 17. Responses for Survey Question 14. State Response (Documents and/or Website) AR ARDOT Standard Specifications for Highway Construction 2014 edition http://web/standard_specifications.aspx CA http://www.dot.ca.gov/design/lap/landscape-design/roadside-toolbox/index.html ID https://apps.itd.idaho.gov/apps/manuals/OperationsManual/Operations_Manual.pdf https://itd.idaho.gov/env/?target=BMP-Manual/ Table 18 lists individual responses for Question 15, providing respondentsâ details of VMS implementation if they do not have an established protocol. Table 18. Responses for Survey Question 15. State Response (Details) ID We only have a protocol for mowing and non-irrigated vegetation. https://apps.itd.idaho.gov/apps/manuals/OperationsManual/Operations_Manual.pdf KY Chip seal is commonly used as a VMS on most new road construction and rehabilitation of existing highways. Concrete apron is used as a VMS on all median cable barrier. Table 19 has the responses for the types of non-herbicide VMSs used. The most common VMS types reported by the respondents are minor concrete pavement, asphalt, gravel, and native and non-irrigation vegetation. Table 19. Responses for Survey Question 16. State Types of Non-herbicide VMS* MCP SCP ACP AC RB RWM GM OM WCM IOV NIV Other KS, SC, TN, VA, VT, WV N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A AR Yes No Yes No No No Yes No No No Yes Yes CA Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No CT No No Yes No No No Yes No No No No No ID Yes No No No Yes No Yes No Yes Yes Yes No IN Yes No Yes No No No No No No No Yes Yes KY Yes No No Yes No No No No No No No No ND No No Yes No No No No No No No No No NV No No No No Yes No Yes No Yes Yes Yes No RI No No No No No No No Yes No No No Yes TX Yes Yes Yes Yes No Yes No Yes Yes No No Yes Total 6 2 6 3 3 2 5 3 4 3 5 4 * MCP = minor concrete pavement, SCP = standard concrete pavement, ACP = asphalt concrete pavement, AC = asphalt composite, RB = rock blanket, RWM = rubber weed mat, GM = gravel mulch, OM = organic mulch, WCM = weed control mat (fiber), IOV = irrigated/ornamental vegetation, NIV = native and non-irrigated vegetation Individual responses for Question 15 include asphalt millings used by Indiana and Rhode Island. Arkansas and Texas use rock rip rap, a rocky rubble material that is placed on roadsides. Question 17 requested information regarding alternative types of VMS usage. Table 20 shows the responses. A malfunction with the survey question did not allow for multiple selections.
48 Table 20. Responses for Survey Question 17. State Response (Other Types of VMS Usage) CA Crumbcreteâversion of concrete using crumb rubber as the aggregate. ID https://apps.itd.idaho.gov/apps/manuals/OperationsManual/Operations_Manual.pdf https://itd.idaho.gov/env/?target=BMP-Manual/ TX Rock riprap is placed under bridges and low light areas. Question 18 requested information regarding the reasons for discontinuation of using a specific non-herbicide VMS. California reported the inadequate longevity of weed control fiber mats and rubber mats; it also cited the cost and additional requirements of using concrete. Table 21 shows the responses regarding the selection criteria used to choose which type of non- herbicide VMS should be used. Table 21. Responses for Survey Question 19. State Roadway Context Roadway Classification Aesthetics Performance of Roadside Appurtenances Other CT, IN, KS, SC, TN, VA, VT, WV N/A N/A N/A N/A N/A AR Yes No No No No CA Yes Yes Yes Yes Yes ID No No No No Yes KY No Yes No No No ND No No No No Yes NV No No Yes No No RI No No No Yes No TX Yes Yes No No No Table 22 shows the responses of agencies that selected âotherâ for Question 19. Table 22. Responses for Survey Question 19. State Response (Other) CA Roadway context, classification, geometry, aesthetics ID All of the above ND Standard practice Table 23 provides details that the agencies consider important for inclusion in a guidance tool for selecting appropriate non-herbicide VMSs. Indiana reported ease and cost of installation and maintenance to be important details used as guidance. California listed the cost-benefit ratio, longevity, and ease of replacement. Idaho reported the type and longevity of both short- and long-term VMSs, the environments where it would be most effective, cost, and installation and maintenance needs.
49 Table 23. Responses for Survey Question 20. State Response CA ⢠Mainline structural section for treatments in gore areas ⢠Maintenance preference for selection of VMS treatments ⢠Corridor themes for the type of treatment and color preferences ⢠Cost-benefit ratio ⢠Longevity ⢠Ease of replacement ⢠Context sensitivity, considering any existing corridor master plans, ease of maintenance (we do not use rock blanket where maintenance can use sweepers because they say that it requires hand sweeping/blowing), stormwater considerations, fire safety (wood mulch vs. gravel mulch), and overall cost CT We would focus efforts on environmentally sensitive areas. ID Consideration should include short-term VMSs (including type and longevity) and long- term VMSs (including type and longevity), area(s) or environment where it is most effective and practical, selection criteria (listed above), cost, installation, and maintenance needs of the item, etc. IN ⢠Cost of installation ⢠Cost to maintain ⢠Ease of installation ⢠Ease of maintenance. TX Been using concrete on all guardrail and cable barriers across the state. Summary of Survey Results The results of the survey of practice revealed few new and innovative practices by the DOTs. Most of the VMSs listed are those found in the 2011 AASHTO Guidelines for Vegetation Management (AASHTO 2011a). Researchers found difficulty in gathering information because VMSs are often not specified as such. They are part of a greater design/construction element. While the material used serves as a VMS, it is not designated as such in the design/construction specifications and details. For example, placing concrete under guardrail is part of many guardrail construction manuals and/or specifications. One of the main reasons for using concrete under guardrail is to prevent vegetative growth at that location. However, concrete at similar locations is generally not labeled as a VMS. Searches within DOT websites and other online sources for VMSs led to herbicide-related vegetation management practices. OTHER STATE DOT PRACTICES THAT PERFORM AS VMSS The research also collected information about other DOT practices that are not defined as a VMS in state DOT design specifications but behave as a VMS. Examples include: ⢠Alabama DOTâs Standard Specifications for Highway Construction, 2006 edition (Alabama Department of Transportation 2006) o Aggregate slope protection o Riprap o Slope paving slope o Concrete median strip ⢠ARDOT Standard Specification for Highway Construction, 2014 edition (ARDOT 2014)
50 o Concrete island (Section 632) ⢠Arizona Department of Transportation (ADOT) Standard Specifications for Road and Bridge Construction (ADOT 2008) o Concrete gore paving (Item 919-1) ⢠Colorado Department of Transportation (CDOT) Standard Specifications for Road and Bridge Construction (CDOT 2017) o Median cover material using bituminous median cover material, concrete, patterned concrete, and/or stone ⢠Minnesota Department of Transportation (MnDOT) Standard Specifications for Construction, 2018 edition (MnDOT 2018) o Slope paving choices of concrete and stabilized aggregate ⢠Wyoming Department of Transportation (WYDOT) Standard Specifications for Road and Bridge Construction (WYDOT 2010) o Minor concrete paving
