Long-Term Vegetation Management Strategies for Roadsides and Roadside Appurtenances (2023) / Chapter Skim
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8 CHAPTER 2. LITERATURE REVIEW Finding solutions for non-herbicide VMSs has been a challenge for transportation agencies.
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9 The VMSs have three basic categories that include impervious surfaces, pervious surfaces, and select vegetation establishment. VMSs are designed to cover the designated area and minimize maintenance activities, particularly adjacent to the travel lanes.
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10 MASH provides the following five categories or classes of highway safety appurtenances: 1. Longitudinal barriers 2.
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11 cognizant of potential effects between a VMS that is placed on the non-traffic side of the barrier and any other safety feature that is installed behind the barrier. For example, pavers placed between a barrier and a signpost will have some mass and/or rigidity that can be displaced by an errant vehicle impact.
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12 criteria (Moran et al.
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13 Figure 3. Guardrail Post Details in Rock Formation (AASHTO 2011b)
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14 Truck- and Trailer-Mounted Attenuators and Portable Work Zone Traffic Control Trailers Truck- and trailer-mounted attenuators (TMAs) and work zone traffic control trailers are portable devices that are normally deployed in temporary applications.
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15 Figure 4. Multidirectional Slip Base for Small Signs (AASHTO 2011b)
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16 Figure 5. Example of a Cast Aluminum Frangible Luminaire (AASHTO 2011b)
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17 safety appurtenance together as a system. As of January 1, 2011, all newly developed hardware must be tested following MASH criteria.
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18 rocky soils. The posts were installed in holes drilled in concrete, constructed by drilling three 203-mm diameter holes on 165-mm centers to a depth of 610 mm.
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19 guardrail system with steel posts in a concrete mow strip performed acceptably for both MASH Tests 3-10 and 3-11. The steel post W-beam guardrail system in a concrete mow strip is considered to have acceptable performance in accordance with the criteria for MASH TL-3 longitudinal barriers.
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20 Figure 8. Minor Concrete Used for Vegetation Management (Caltrans 2017b)
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21 systems.
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22 Figure 11. Stamped Asphalt Concrete at Roundabout (Pattern Paving Products 2016)
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23 to move during a guardrail impact. In addition, asphalt composite has a low life cycle cost.
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24 Figure 14. Rock Blanket Installations (Diversified Landscape Company 2016, Caltrans 2015)
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25 Figure 15. Rubber Weed Mat (Caltrans 2017e)
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26 Glass Cullet Glass cullet consists of recycled glass processed into a mulch material (see Figure 17)
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27 Figure 18. Gravel Mulch Treatment at the Roadside (TxDOT 2017)
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28 Figure 20. Organic Mulch (Pacific Landscape Supply 2019)
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29 locations (Caltrans 2017i)
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30 Comparison of Commonly Used VMSs Table 2 shows a comparison of the commonly used VMSs. Approximate costs for each VMS were obtained from Caltrans (2017a)
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31 VMS Benefits Limitations Installation Cost per Square Yard Organic mulch • Retains soil moisture • Enhances soil structure • Provides erosion control • Temporary solution • Degrades over time • 2- to 3-year life cycle $40* Weed control fiber mat • Allows for infiltration • UV stable and fire retardant • Easy repairs/replacement • Retrofit applicable but more expensive • Subject to damage from wind, mowers, and winter maintenance equipment $50*
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32 Figure 24. Concrete Canvas® GCCM Section (Concrete Canvas 2020)
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33 examined three herbicide formulations, four weed control barriers, and competitive vegetation. The four VMSs investigated included: • Permeable recycled fiber mat • Permeable recycled fiber mat customized to fit the edge of the roadway and variances in guardrail post width • Semi-rigid, interlocking panels made of 100 percent recycled plastic (this product is no longer available)
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34 Barton and Budischak (2013) found that weed control barriers are difficult to install in retrofit applications.
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35 Table 4. DelDOT VMS Suitability and Weed Control Rating (Barton and Budischak 2013)
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36 Figure 27. TxDOT Demonstration Project Using Crumb Rubber VMS (TxDOT 2012)
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37 impervious VMSs is best under guardrail, especially in environmentally sensitive areas that prohibit the use of herbicide control treatments. The research looked at eastern and western Washington climates to determine the effects of climate on the product installation and performance.
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38 VMS Location Product Description Maintenance Costs Findings/Recommendations Pavement Under guardrail Pavement under guardrail $895/mile/year Of all the under-guardrail barriers, this is the least expensive to install and most durable. Maintenance costs would be comparable to those above ($22/mile)
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39 required to maintain compliance with the RDG and MASH as well as requirements specific to the respective DOT. Many barrier systems are undergoing retesting for compliance.
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