Long-Term Vegetation Management Strategies for Roadsides and Roadside Appurtenances (2023)

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73 APPENDIX C: INTERACTIVE SELECTION TOOL INFORMATION SHEETS AGGREGATE BASE Description: Compactable aggregate base placed on prepared surface and compacted to 90–5% Typical Locations:  Cable barrier  Support posts and poles  Edge of pavement  Gore/median  Guardrail  Mow edge  Slope/embankment Advantages:  Low-cost treatment applicable for new construction and retrofit locations  Aesthetic value determined by aggregate color and type  Can be used in most climate conditions  Uses standard installation/maintenance equipment  Allows for storm water infiltration Limitations and Common Problems:  May not be applicable in areas with snow removal equipment and snow storage  Displacement by errant vehicles and maintenance equipment  May require spot herbicide treatment and re-compaction Relative Costs Installation Moderate Life Cycle Moderate Maintenance Low Repair Low Effective Longevity Moderate Level of Difficulty Installation Low Repair Low Maintenance Low Retrofit Low

74 ASPHALT COMPOSITE Description: Single-step, seamless, cold-spray-applied asphalt emulsion reinforced with fiberglass strands. Site preparation consists of general grubbing, compaction, and application of pre-emergent herbicide to provide a relatively smooth surface to place the product. Typical Locations:  Cable barrier  Support posts and poles  Gore/median  Guardrail  Mow edge Advantages:  Flexible, durable, and solid barrier  Adheres to asphalt, concrete, wood, and metal  Installed using typical maintenance equipment/practices  Low life cycle costs  Low cost and easy installation and repairs  Applicable for new construction and retrofit locations  Seamless installation to reduce vegetation encroachment at seams  Rapid, single-step, high-rate application minimizes lane closure and worker exposure  Safe for use near water runoff areas  Can withstand machine traffic Limitations and Common Problems:  Requires installation temperature >50°  Requires leave-out Relative Costs Installation Low Life Cycle Low Maintenance Low Repair Low Effective Longevity High Level of Difficulty Installation Low Repair Low Maintenance Low Retrofit Low

75 ASPHALT CONCRETE PAVEMENT Description: Standard Type B asphalt concrete mixed, spread, and compacted per DOT specifications. Material thickness varies and is site specific. Typical Locations:  Cable barrier  Support posts and poles  Edge of pavement  Gore/median  Guardrail If using with a strong post guardrail, refer to the STRONG POST GUARDRAIL USE WITH RIGID VMS MATERIALS information sheet for examples of recently tested designs with leave-outs.  Mow edge Advantages:  Generally lower installation cost  Applicable for new construction and uses readily available material  Most contractors and DOTs have equipment and training for installation Limitations and Common Problems:  Leave-outs may be required due to VMS material rigidity. Refer to AASHTO RDG, MASH, recent research, and/or other guidelines to determine leave-out compliance requirements.  Restricted work area may limit use of asphalt concrete installation equipment  Lower installation cost but high life cycle cost when compared to minor concrete  Material degrades in areas not receiving regular compaction from traffic, allowing weed establishment  Small batch base materials may prove problematic and expensive Relative Costs Installation Low/Moderate Life Cycle Moderate Maintenance Moderate Repair Moderate Effective Longevity Moderate Level of Difficulty Installation Moderate Repair Moderate Maintenance Moderate Retrofit Moderate/High

76 CRUMB RUBBER MODIFIED CONCRETE Description: Crumb rubber modified concrete (CRMCrete) is a concrete-based product using a slurry blend of recycled scrap tire crumb rubber material and homopolymer polypropylene high-performance reinforcing fibers. CRMCrete is installed like concrete and can be used with color and texture for increased aesthetic value. This product is comparable in use and characteristics to minor concrete. Typical Applications:  Cable barrier  Support posts and poles  Edge of pavement  Gore/median  Guardrail If using with a strong post guardrail, refer to the STRONG POST GUARDRAIL USE WITH RIGID VMS MATERIALS information sheet for examples of recently tested designs with leave-outs.  Mow edge Advantages:  Color can be added  Formwork is not always necessary  Higher daily production rates—faster than other surface treatments  Easy installation  Uses standard equipment and concrete mixes  Uses recycled tire rubber material Limitations and Common Problems:  Consistency of mix may limit its use on slopes  Limited history of maintainability and life cycle costs  Repairs are difficult to match to the original color if you use a concrete stain  Leave-outs may be required due to VMS material rigidity. Refer to AASHTO RDG, MASH, recent research, and/or other guidelines to determine leave-out compliance requirements. Relative Costs Installation Low/Moderate Life Cycle Low Maintenance Low Repair High Effective Longevity High Level of Difficulty Installation Low/Moderate Repair High Maintenance Moderate Retrofit High

77 GEOSYNTHETIC CEMENTITIOUS COMPOSITE MATS Description: GCCM is a flexible cement-impregnated fabric that hardens when hydrated to form a thin, durable concrete layer. This material has different proprietary name such as Concrete Cloth™ and Concrete Canvas®. This VMS consists of a dry concrete mix, reinforcing fiber matrix, fabric top surface, and poly vinyl chloride (PVC) bottom coating for waterproofing. Typical Locations:  Cable barrier  Support posts and poles  Gore/median  Guardrail If using with a strong post guardrail, refer to the STRONG POST GUARDRAIL USE WITH RIGID VMS MATERIALS information sheet for examples of recently tested designs with leave-outs.  Mow edge  Slope/embankment Advantages:  Rapid and easy installation  Product comes on a roll so no concrete mixing  Waterproof and fireproof  Flexible enough to allow material to conform to surface  Unset material can be cut as necessary for given situation Limitations and Common Problems:  Leave-outs may be required due to VMS material rigidity. Refer to AASHTO RDG, MASH, recent research, and/or other guidelines to determine leave-out compliance requirements.  Limited available information regarding VMS interaction, long-term cost, performance, and maintenance as a VMS Relative Costs Installation N/A Life Cycle N/A Maintenance N/A Repair N/A Effective Longevity N/A Level of Difficulty Installation Low Repair Low Maintenance N/A Retrofit Low

78 GLASS CULLET Description: Crushed glass (cullet) particles are generally angular in shape and can contain some flat and elongated particles depending on the degree of processing (i.e., crushing). Typical Locations:  Cable barrier  Support posts and poles  Edge of pavement  Gore/median  Guardrail Advantages: • Aesthetic qualities • Works well for flat areas • Does not decompose • Wide variety of colors and sizes available • Uses recycled material Limitations and Common Problems:  Not recommended for use on slopes  Reflective—glare issue and reflects the underlayment  Proper processing is required  Supportive border may be necessary  Limited information regarding long-term cost, performance, and maintenance as a VMS Relative Costs Installation Low Life Cycle Low Maintenance Low Repair Low Effective Longevity High Level of Difficulty Installation Low Repair Low Maintenance Low Retrofit Low

79 GRAVEL MULCH Description: Graded, crushed rock placed on geosynthetic fabric (herbicide or non-herbicide treated) Typical Locations:  Support posts and poles  Edge of pavement  Gore/median  Slope/embankment Advantages:  Low-cost treatment for new construction and retrofit  Aesthetic value determined by gravel color and texture  Can be used in most climate conditions  Uses standard installation/maintenance equipment  Allows for storm water infiltration Limitations and Common Problems:  May not be applicable in areas with snow removal equipment and snow storage  Displacement by errant vehicles and maintenance equipment  Requires removal of windblown debris  Subject to voids filling with windblown soil, allowing weed development  Gravel should be placed approximately 1–2 inches thick. Finish grade of gravel should be equal to adjacent grade and flow lines. Relative Costs Installation Low Life Cycle Low Maintenance Low Repair Low Effective Longevity Moderate Level of Difficulty Installation Low Repair Low Maintenance Low Retrofit Low

80 IRRIGATED ORNAMENTAL VEGETATION Description: Low-growing species that out-competes undesired vegetation. This may include native and/or non- native vegetation. Typical Locations:  Gore/median  Slope/embankment Advantages:  High aesthetic value  Uses standard installation/maintenance equipment  Applicable for new construction and retrofit  Allows for storm water infiltration  Provides erosion control  Out-competes weeds when established Limitations and Common Problems:  * Worker exposure is high for installation and maintenance  Requires site preparation  Plant establishment period subject to increased maintenance  Costs subject to extent of landscape development  Limited use in arid/semi-arid locations  Limited use in areas subject to fire hazard  Subject to climate effects  Subject to damage and displacement from errant vehicles, wind, mowers, and snow removal equipment Relative Costs Installation High Life Cycle Moderate/High Maintenance Moderate Repair Moderate Effective Longevity Moderate Level of Difficulty* Installation Moderate Repair Moderate Maintenance Moderate Retrofit Moderate

81 MINOR CONCRETE PAVEMENT Description: Standard concrete that includes crumb rubber or polypropylene fibers Typical Locations:  Cable barrier  Support posts and poles  Edge of pavement  Gore/median  Guardrail If using with a strong post guardrail, refer to the STRONG POST GUARDRAIL USE WITH RIGID VMS MATERIALS information sheet for examples of recently tested designs with leave-outs.  Mow edge  Slope/embankment Advantages:  Comparable cost to standard concrete paving  Easily installed with standard tools and equipment  Aesthetic value determined by use of colors and patterns Limitations and Common Problems:  Leave-outs may be required due to VMS material rigidity. Refer to AASHTO RDG, MASH, recent research, and/or other guidelines to determine leave-out compliance requirements.  Not recommended for retrofit locations such as existing guardrails due to grading and excavation required for installation Relative Costs Installation Moderate/High Life Cycle Cost Low Maintenance Low Repair High Effective Longevity High Level of Difficulty Installation Moderate Repair High Maintenance Moderate Retrofit High

82 MODULAR PAVING UNITS Description: Generally concrete or brick paving units available in a variety of shapes, colors, and structural characteristics Typical Locations:  Support posts and poles  Gore/median  Mow edge  Slope/embankment Advantages:  High aesthetic appeal—variety of colors and patterns  Good for use in urban/high-visibility locations  Applicable for new construction and retrofit  Can be used in most climate conditions  Most contractors have installation equipment  Allows easy repairs and access to subsurface utilities  Can be specified for pedestrian or vehicle traffic  Used with or without mortar  Can be set on impervious or pervious base Limitations and Common Problems:  * Worker exposure is high for installation  Requires supportive edge  Can be dislodged by heavy vehicle traffic  Can be used under guardrail but not considered a typical location  Subject to damage and displacement from errant vehicles, mowers, and snow removal equipment  Subject to voids filling with windblown soil, allowing weed development  Limited slope applications if not set in mortar  Leave-outs may be required due to VMS material rigidity. Refer to AASHTO RDG, MASH, recent research, and/or other guidelines to determine leave-out compliance requirements.  If using with a strong post guardrail, refer to the STRONG POST GUARDRAIL USE WITH RIGID VMS MATERIALS information sheet for examples of recently tested designs with leave-outs. Relative Costs Installation Moderate/High Life cycle Low Maintenance Low Repair Low Effective Longevity High Level of Difficulty Installation* Moderate/High Repair Low Maintenance Low Retrofit Moderate

83 NATIVE AND NON-IRRIGATED VEGETATION Description: Low-growing species that out-compete undesired vegetation. This may include native and/or non- native vegetation. Typical Locations:  Cable barrier  Edge of pavement  Gore/median  Guardrail  Slope/embankment Advantages:  High aesthetic value  Applicable for new construction and retrofit  Uses standard installation/maintenance equipment  Allows for storm water infiltration  Provides erosion control  Out-competes weeds when established Limitations and Common Problems:  *Worker exposure is high for installation and maintenance  Requires site preparation  Plant establishment period subject to increased maintenance  Limited use in arid/semi-arid locations  Limited use in areas subject to fire hazard  Subject to climate effects  Subject to damage and displacement from errant vehicles, wind, mowers, and snow removal equipment  Subject to effects of winter operations Relative Costs Installation Low/Moderate Life Cycle Low/Moderate Maintenance Low/Moderate Repair Low/Moderate Effective Longevity Moderate Level of Difficulty* Installation Moderate Repair Moderate Maintenance Moderate Retrofit Moderate

84 ORGANIC MULCH Description: Consists of surface-applied, mulched recycled materials such as chipped wood and bark usually placed on geosynthetic fabric (herbicide or non-herbicide treated) Typical Locations:  Gore/median  Slope/embankment Advantages:  Can be used in most climate conditions  Uses standard installation/maintenance equipment  Aesthetic value determined by color and texture  Applicable for new construction and retrofit  Allows for storm water infiltration  Provides erosion control  Uses recycled materials Limitations and Common Problems:  Limited longevity—2 to 3 years  A 4-inch layer mulch depth should be reapplied every 2 to 3 years  Subject to degradation  May require reapplication  May not be suitable for slopes greater than 1V:3H without tackifier  Not suitable in areas subject to fire hazard  Subject to damage and displacement from errant vehicles, wind, mowers, and snow removal equipment  Subject to voids filling with windblown soil, allowing weed development Relative Costs Installation Low Life Cycle Moderate/High Maintenance Moderate Repair Low Effective Longevity Low Level of Difficulty Installation Low Repair Low Maintenance Low Retrofit Low

85 PATTERNED CONCRETE PAVEMENT Description: Standard concrete mixture using color additive and stamped pattern Typical Locations:  Cable barrier  Support posts and poles  Edge of pavement  Gore/median  Guardrail If using with a strong post guardrail, refer to the STRONG POST GUARDRAIL USE WITH RIGID VMS MATERIALS information sheet for examples of recently tested designs with leave-outs.  Mow edge  Slope/embankment Advantages:  High aesthetic appeal—variety of colors and patterns  Good for use in urban/high-visibility locations  Can be used in most climate conditions  Applicable for new construction and limited retrofit  Low life cycle cost  Most contractors have equipment to install Limitations and Common Problems:  High installation and repair costs—may be difficult to match color and pattern for repair  Not recommended for retrofit locations such as existing guardrails  Leave-outs may be required due to VMS material rigidity. Refer to AASHTO RDG, MASH, recent research, and/or other guidelines to determine leave-out compliance requirements.  May be damaged by snow removal equipment  Subject to voids filling with windblown soil, allowing weed development Relative Costs Installation High Life Cycle Cost Moderate Maintenance Moderate/High Repair High Effective Longevity High Level of Difficulty Installation High Repair High Maintenance Moderate Retrofit High

86 RECYCLED ASPHALT MILLINGS Description: Compacted recycled asphalt from asphalt milling operations Typical Locations:  Cable barrier  Edge of pavement  Guardrail  Mow edge Advantages:  Can be used in most climate conditions  Applicable for new construction and retrofit  Low life cycle cost  Most contractors have equipment to install  Uses recycled materials from milling operations  Leave-outs are not required Limitations and Common Problems:  Subject to availability  May become dislodged if not compacted properly  Subject to loss of compaction over time, allowing weed development Relative Costs Installation Low Life Cycle Low Maintenance Low Repair Low Effective Longevity Low Level of Difficulty Installation Low Repair Low Maintenance Low Retrofit Low

87 ROCK BLANKET Description: Rock cobble installed using mortar with or without concrete base Typical Locations:  Support posts and poles  Gore/median  Slope/embankment Advantages:  Aesthetic value determined by color and texture  Good for use in urban/high-visibility locations  Applicable for new construction and limited retrofit  Can be used in most climate conditions  Low life cycle cost  Most contractors have equipment to install Limitations and Common Problems:  High installation and repair costs if set in mortar  Can be difficult in retrofit applications due to size of cobble  Leave-outs may be required due to VMS material rigidity. Refer to AASHTO RDG, MASH, recent research, and/or other guidelines to determine leave-out compliance requirements. Relative Costs Installation High Life Cycle Low Maintenance High Repair High Effective Longevity High Level of Difficulty Installation Moderate Repair High Maintenance Low Retrofit High

88 ROCK SLOPE PROTECTION Description: Rock cobble placed on geosynthetic fabric (herbicide or non-herbicide treated) Typical Locations:  Gore/median  Slope/embankment Advantages:  Provides erosion control  Can be used in most climate conditions  Low life cycle cost  Most contractors have equipment to install  Aesthetic value determined by color and texture  Applicable for new construction and retrofit Limitations and Common Problems: • Limited application areas • Maximum slope 1V:2H • Subject to voids filling with windblown soil, allowing weed development • May require spot herbicide treatments Relative Costs Installation Low Life Cycle Low Maintenance Low Repair Low Effective Longevity Moderate Level of Difficulty Installation Low Repair Low Maintenance Low Retrofit Low

89 RUBBER WEED MAT Description: Mats consisting of recycled rubber tires adhered together with a resin. Cutouts are often provided for post placement. Typical Locations:  Cable barrier  Support posts and poles  Guardrail Advantages:  No staking/anchoring is required  Easy to install and replace but is very time consuming, thereby increasing worker exposure  Different colors available  Applicable for new construction and retrofit Limitations and Common Problems:  Long worker exposure time due to slow installation process  Potential joint separation if not installed/sealed properly  Subject to damage from wind, mowers, snow removal equipment; joint separation; and UV degradation Relative Costs Installation Moderate/High Life Cycle Low Maintenance Low Repair Low Effective Longevity High Level of Difficulty Installation High Repair Moderate Maintenance Low Retrofit High

90 STAMPED ASPHALT PAVEMENT Description: Economical aesthetic treatment for standard asphalt concrete. An imprint tool is used to create pattern(s) while asphalt is still warm and pliable. Typical Locations:  Support posts and poles  Edge of pavement  Gore/median  Mow edge Advantages:  Installation and repair can be done by standard maintenance equipment  Aesthetic value determined by colors and patterns  Faster installation than stamped concrete or pavers, so less worker exposure time to traffic  Applicable for new construction Limitations and Common Problems:  Use on slopes is difficult for stamping equipment  Leave-outs may be required due to VMS material rigidity. Refer to AASHTO RDG, MASH, recent research, and/or other guidelines to determine leave-out compliance requirements.  Difficult to match colors during repair  UV degradation of color may occur  Deformation or cracking may occur  Subject to surface scaring Relative Installation Cost Installation Moderate/High Life Cycle Moderate Maintenance High Repair High Effective Longevity Moderate Level of Difficulty Installation Moderate/High Repair High Maintenance Moderate Retrofit High

91 STANDARD CONCRETE PAVEMENT Description: Standard concrete mixture Typical Locations:  Cable barrier  Support posts and poles  Edge of pavement  Gore/median  Guardrail If using with a strong post guardrail, refer to the STRONG POST GUARDRAIL USE WITH RIGID VMS MATERIALS information sheet for examples of recently tested designs with leave-outs.  Mow edge  Slope/embankment Advantages:  Aesthetic value determined by color and texture  Applicable for new construction and limited retrofit  Can be used in most climate conditions  Low life cycle cost  Most contractors have equipment to install Limitations and Common Problems:  High installation and repair costs  Can be difficult in retrofit applications such as existing guardrails due to grading and excavation required for installation  Leave-outs may be required due to VMS material rigidity. Refer to AASHTO RDG, MASH, recent research, and/or other guidelines to determine leave-out compliance requirements. Relative Installation Cost Installation High Life Cycle Low Maintenance Low Repair High Effective Longevity High Level of Difficulty Installation Moderate Repair High Maintenance Moderate Retrofit High

92 WEED CONTROL FIBER MAT Description: Mats consisting of synthetic polyester fibers made from recycled plastic Typical Locations:  Cable barrier  Support posts and poles  Guardrail Advantages:  Can be used in most climate conditions  Applicable for new construction and retrofit  Uses standard installation/maintenance equipment  Allows for storm water infiltration  Fire retardant  Variable width rolls to 6 feet  Not subject to UV degradation  Available in various colors for aesthetic appeal  Applicable for new construction and retrofit Limitations and Common Problems:  Areas at ground penetrations should be sealed with caulk or similar material  Subject to damage from wind, mowers, and snow removal equipment  Displacement by errant vehicles and maintenance equipment Relative Costs Installation Moderate/High Life Cycle Low Maintenance Low Repair Low Effective Longevity High Level of Difficulty Installation Low Repair Low Maintenance Low Retrofit Moderate

93 STRONG POST GUARDRAIL USE WITH RIGID VMS MATERIALS The VMSs identified and presented do not present specific design guidance for highway safety appurtenances, nor are they a substitute for any other highway design practice. The user should refer to the AASHTO RDG, MASH for successfully tested hardware, and any specific state DOT practices for warrants, proper placement, and maintenance of roadside safety appurtenances when applying these VMSs (AASHTO 2011b, 2016). In addition, before applying any of the techniques described on a proprietary roadside safety hardware device (e.g., guardrail terminal, crash cushion, or breakaway sign support), the manufacturer should be contacted to discuss the potential for the treatment to adversely affect the performance of the manufacturer’s safety hardware device. Mow strips prevent vegetation growth several feet around guardrail installations, including cable barriers, W-beam guardrail, guardrail transitions, and guardrail end treatments. W-beam guardrail posts, guardrail transition posts, and guardrail end treatment posts are treated equally with regard to the application of VMSs. As previously stated, a VMS should not be applied to any proprietary guardrail end treatment without consulting first with the product manufacturer. Mow strips are typically asphaltic or concrete pavement and vary in thickness from several inches up to 200 mm (8 inches) maximum. Strong post W-beam guardrail posts in mow strips and rock formations face similar problems with regard to facilitating rotation of the strong posts. Details for installation of strong steel post W-beam guardrail posts in mow strips have been developed, which differ from that in rock formations. These details were originally developed and crash tested for use with both steel and wood posts in accordance with NCHRP Report 350 (Ross et al. 1993). More recent research and full-scale MASH testing have been conducted for strong post W-beam guardrail in mow strips with leave-outs, the portion of the mow strip omitted around the base of the post to allow for post rotation. The 31-inch W-beam guardrail system with steel posts in concrete mow strip performed acceptably for both MASH Tests 3-10 and 3-11, and therefore the steel post W-beam system in concrete mow strip is considered acceptable for MASH Test Level Three (TL-3) longitudinal barrier (Sheikh et al. 2019, Moran et al. 2020). In this design, the critical measurement of the leave-out installation is from the back of the post to the edge of the mow strip; this measurement should be a minimum of 175 mm (7 inches). Yet wood post W-beam guardrail testing did not meet MASH TL-3 safety requirements in all cases. Strong post guardrail with 6-inch by 8-inch rectangular wood posts and 7½-inch-diameter round wood posts both failed to meet the MASH TL-3 criteria when installed in mow strips with leave-outs. However, a modified round wood post system with 36-inch embedment (Moran et al. 2020) was full-scale crash tested in a mow strip with leave-outs and did meet MASH TL-3 safety requirements. These recent findings suggest that leave-outs remain a viable method for use in mow strips with steel post W-beam guardrail systems. Wood post W-beam guardrail systems appear to be more sensitive to the use of mow strips and may require further research and/or development of design modifications. The critical feature of the mow strip installation is the portion of the mow strip around the post omitted for the post rotation, also known as the leave-out. The leave-out’s critical measurement is from the back of the post to the edge of the mow strip and should be a minimum of 175 mm (7 inches). For illustrative purposes, Figure 1 shows the detail from the AASHTO RDG (AASHTO 2011b). Leave-outs can be filled with low-strength grout, a two-part polyethylene foam, or other material that has a compressive strength of 0.85 MPa (120 psi) or less. During an impact, the leave-out material allows for some degree of post rotation by deforming or crushing prior to generating sufficient force to cause post failure. Failure of the sacrificial leave-out backfill material also minimizes damage to the surrounding mow strip. Some states backfill with a coarse aggregate material and seal the surface with an asphaltic sealer material. As previously discussed, this is an active area of research and design evolution, and the RDG has not been updated and is out of date for some applications. Always check that a mow strip design has been evaluated in accordance with MASH.

94 For strong steel post W-beam guardrail posts installed in asphalt or concrete surfacing that is thicker than 200 mm (8 inches), refer to Figure 2 showing AASHTO RDG Figure 5-5l (b) for installation in rock formations (AASHTO 2011b). For these installations, the backfill around the posts is typically a coarse aggregate material. In some locations, it may be beneficial to seal the surface with an asphaltic crack sealant or other similar material to reduce water infiltration Figure 1. AASHTO RDG Guardrail Post Detail in Mow Strip Application (AASHTO 2011b). Figure 2. Guardrail Post Details in Rock Formation (AASHTO 2011b). TxDOT sponsored MASH testing of W-beam guardrail with 36-inch soil embedded, 7½-inch-diameter round wood posts in a concrete mow strip as shown in Figure 3. The tested configuration met the safety performance evaluation guidelines for MASH TL-3 longitudinal barriers. The crash test performed was in accordance with MASH Test 3-11, which involves a 2270P vehicle impacting the TxDOT W-beam guardrail with 7½-inch-diameter round wood posts in a concrete mow strip at a target impact speed and impact angle of 62 mi/h and 25 degrees, respectively.

95 Figure 3. Round Wood Post in Concrete Mow Strip (Moran et al. 2020). The 31-inch W-beam guardrail system with steel posts in a concrete mow strip (Figure 4) performed acceptably for both MASH Tests 3-10 and 3-11, and therefore the steel post W-beam system in a concrete mow strip is considered acceptable for MASH TL-3 longitudinal barrier (Moran et al. 2020). Figure 4. W-beam Guardrail in Concrete Mow Strip (Moran et al. 2020). Summary VMSs applied in and around highway safety appurtenances should be done so cognizant of their effect on the performance of everything in the highway design environment. If a VMS is thought to possibly have a performance effect on a highway safety appurtenance, then consideration should be given to crash testing the VMS and safety appurtenance together as a system. As of January 1, 2011, all newly developed hardware must be tested using MASH. Of particular interest to the application of VMSs, the FHWA also issued a memorandum dated January 7, 2016, regarding the federal-aid eligibility of highway safety hardware after December 31, 2016, and the following applies to VMSs (FHWA 2016):  FHWA will no longer issue eligibility letters for highway safety hardware that has not been successfully crash tested to the 2016 edition of MASH.  Modifications of eligible highway safety hardware must use criteria in the 2016 edition of MASH for reevaluation and/or retesting.  Non-significant modifications of eligible hardware that have a positive or inconsequential effect on safety performance may continue to be evaluated using finite element analysis.

96 For More Information AASHTO. 2011a. Guidelines for Vegetation Management, first edition. Washington, DC. AASHTO. 2011b. Roadside Design Guide, fourth edition. Washington, DC. AASHTO. 2016. Manual for Assessing Safety Hardware, second edition. Washington, DC. FHWA. 2016. Memorandum, Joint Implementation Agreement for Manual for Assessing Safety Hardware. https://safety.fhwa.dot.gov/roadway_dept/countermeasures/reduce_crash_severity/docs/memo_joint_impleme ntation_agmt.pdf. FHWA. 2020. Roadway Departures: Frequently Asked Questions: Barriers, Terminals, Transitions, Attenuators, and Bridge Railings. https://safety.fhwa.dot.gov/roadway_dept/countermeasures/faqs/qa_bttabr.cfm. FHWA. 2022. Proven Safety Countermeasures. FHWA-SA-17-060. https://safety.fhwa.dot.gov/provencountermeasures. FHWA. N.d. Guardrail 101. https://www.fhwa.dot.gov/guardrailsafety/guardrail101.pdf. Fitzgerald, W. 2008. W-Beam Guardrail Repair: A Guide for Highway and Street Maintenance Personnel. FHWA-SA- 08-002. https://safety.fhwa.dot.gov/local_rural/training/fhwasa08002/. Ross, H., D. Sicking, R. Zimmer, and J. Miche. 1993. NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_350-a.pdf. Moran, S., R. Bligh, W. Menges, G. Schroeder, and D. Kuhn. 2020. MASH Test 3-11 Evaluation of TxDOT W-Beam Guardrail with 7½-Inch Diameter Round Wood Posts in Concrete Mow Strip. Report 0-6968-R2. TxDOT. Sheikh, N., W. Menges, and D. Kuhn. 2019. MASH TL-3 Evaluation of 31-Inch W-Beam Guardrail with Wood and Steel Posts in Concrete Mow Strip. Roadside Safety Research Program Pooled Fund Study No. TPF-5 (114). https://www.roadsidepooledfund.org/wp-content/uploads/2017/06/TRNo608551-1-45-Final.pdf. Task Force 13. Standardized Highway Barrier Hardware Guide. http://www.tf13.org/Barrier-Hardware.php