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Suggested Citation:"II. State of the Practice ." National Academies of Sciences, Engineering, and Medicine. 2010. Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report. Washington, DC: The National Academies Press. doi: 10.17226/22938.
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Suggested Citation:"II. State of the Practice ." National Academies of Sciences, Engineering, and Medicine. 2010. Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report. Washington, DC: The National Academies Press. doi: 10.17226/22938.
×
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Suggested Citation:"II. State of the Practice ." National Academies of Sciences, Engineering, and Medicine. 2010. Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report. Washington, DC: The National Academies Press. doi: 10.17226/22938.
×
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Suggested Citation:"II. State of the Practice ." National Academies of Sciences, Engineering, and Medicine. 2010. Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report. Washington, DC: The National Academies Press. doi: 10.17226/22938.
×
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Suggested Citation:"II. State of the Practice ." National Academies of Sciences, Engineering, and Medicine. 2010. Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report. Washington, DC: The National Academies Press. doi: 10.17226/22938.
×
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Suggested Citation:"II. State of the Practice ." National Academies of Sciences, Engineering, and Medicine. 2010. Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report. Washington, DC: The National Academies Press. doi: 10.17226/22938.
×
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Suggested Citation:"II. State of the Practice ." National Academies of Sciences, Engineering, and Medicine. 2010. Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report. Washington, DC: The National Academies Press. doi: 10.17226/22938.
×
Page 9
Page 10
Suggested Citation:"II. State of the Practice ." National Academies of Sciences, Engineering, and Medicine. 2010. Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report. Washington, DC: The National Academies Press. doi: 10.17226/22938.
×
Page 10
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Suggested Citation:"II. State of the Practice ." National Academies of Sciences, Engineering, and Medicine. 2010. Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report. Washington, DC: The National Academies Press. doi: 10.17226/22938.
×
Page 11

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3 II. STATE OF THE PRACTICE Task 1 – Identify Non-Proprietary Roadside-Safety Features & Frequency of Use by State DOTs Identify non-proprietary roadside-safety features and their frequency of use by state DOTs. This may include review of the FHWA safety hardware website (safety.fhwa.dot.gov/report350hardware) and/or a survey of state DOTs. Results of this task will be a list of roadside-safety features and an indication of how frequently (e.g., high, medium, or low usage) the devices are used by state DOTs. TTI researchers identified the use and frequency of specific non-proprietary roadside- safety features such as longitudinal barriers (guardrails and median barriers); transitions; crash cushions; terminals; and breakaway hardware (i.e. sign and luminaire supports) by: 1) querying FHWA’s web site (http://safety.fhwa.dot.gov/roadway_dept/road_hardware/index.htm) for all pertinent acceptance letters; 2) performing a survey of State Department of Transportation officials; and 3) identifying and reviewing crash test reports that have been performed by the crash testing laboratories to the MASH testing criteria. TTI researchers examined all FHWA acceptance letters and memorandums posted on their web site to identify non-proprietary NCHRP Report 350 safety hardware. Each FHWA acceptance letter or memorandum identified as pertinent to this research effort is not specifically identified herein. However, all the letters are identified in the list of references(3-29). TTI researchers prepared a list of and reviewed non-proprietary hardware from the FHWA acceptance letters issued to date. Applicable crash test reports for the list of non-proprietary hardware were obtained and reviewed, when readily available. In some instances, hardware was accepted by FHWA as being NCHRP Report 350 compliant based on testing performed in accordance with NCHRP Report 230 and the 1985 AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals.(30, 31). This was the case for most small ground-mounted sign supports due to the fact the testing and evaluation criteria for these devices were essentially unchanged in NCHRP Report 350. However, MASH requires small ground-mounted signs be tested with the pickup truck test vehicle to evaluate the potential for penetration of the sign panel and/or support(s) into the occupant compartment through the windshield. FHWA Dwight A. Horne’s memorandum (B-64)(5), dated February 14, 2000 on the subject “Report 350 Nonproprietary Guardrails and Median Barriers” was used to aid in identifying non-proprietary longitudinal roadside and median barriers that have met NCHRP Report 350 requirements at one or more test levels or are considered equivalent to barriers that have been tested and demonstrated acceptable performance. Additionally, a total of eight FHWA letters now exist, identified as B-64 with an alpha character following, that address non-proprietary hardware accepted for use on the NHS. FHWA memorandums SS-25(26) and SS-36(27), dated June 4, 1991 and September 3, 1993, respectively, were used to aid in developing a list of commonly used sign and luminaire supports. The FHWA acceptance letters were used to generate the material in the survey of the State DOTs. No attempt was made to

4 specifically identify in the survey every state that may have some variation of wood sign support accepted for use. A survey of the crash tests performed by the testing laboratories to the MASH conditions was performed. A list of 13 crash test reports performed under NCHRP Project 22-14(02), eleven tests performed by Midwest Roadside Safety Facility (MwRSF) and two crash tests performed by TTI for Texas Department of Transportation (TXDOT) research project FHWA/TX-07/0-5526-1, were obtained. The safety hardware associated with the MASH tests performed was included in the survey. Following identification of non-proprietary safety hardware accepted for use on the NHS, TTI researchers compiled a list of the hardware for use in a survey of the State DOTs. The purpose of the survey was to query appropriate State DOT personnel on the type and frequency of use of non-proprietary roadside-safety features used in their respective state. An internet web-based survey was developed and posted. As necessary, telephone and e-mail interviews were conducted for purposes of clarifying answers. Survey participants were identified through FHWA, the Pooled Fund studies at TTI and Midwest Roadside Safety Facility, panel member participants of previous NCHRP projects, and AASHTO Task Force 13 and Transportation Research Board AFB20 committee members. The survey included a list of non-proprietary roadside safety features, grouped by type. Five check boxes were provided for each device to indicate associated percentages of use: [Never; Rarely (1-25 percent); Somewhat Frequently (26-50 percent); Frequently (51-75 percent); and Very Frequently (76-100 percent)]. Each device name listed on the survey was hyperlinked to the device’s respective FHWA acceptance letter. This enabled the respondent to view the FHWA letter and any associated engineering drawings for clarification of system details. A total of 51 responses were received, representing 44 states. The survey and a summary of participant responses are presented in Appendix A (available on the National Crash Analysis Center [NCAC] website, www.ncac.gwu.edu/). Task 2 – Review All Applicable Information & Create Matrix Review information, such as results of crash tests and finite element modeling, that may be applicable. Create a framework (or matrix) for identifying the roadside hardware features that may need evaluation using the proposed new criteria by test level. Include in this framework, information on judgment of expected performance, results of prior crash tests, and findings of crash simulations. In conjunction with the performance of Task 1, TTI researchers: 1) compiled and reviewed the survey results of the State DOTs use and frequency rates for non-proprietary hardware; and 2) reviewed the test reports of the 13 crash tests performed under NCHRP Project 22-14(02) and TXDOT project FHWA/TX-07/0-5526-1. A prioritized crash testing matrix was developed from the performance of Tasks 1 and 2.

5 Table 1. Weighted Prioritization by Hardware Category. Test Article Tested to MASH Prioritization from Survey Guardrails Strong-Post (Steel) W-Beam  1 Strong-Post (Wood) W-Beam 2 Strong-Post (Steel) Thrie-Beam 3 Strong-Post (Wood) Thrie-Beam 4 Low-Tension Cable (3-Strand) 5 Midwest Guardrail System (MGS)  6 Weak-Post Box-Beam 7 Strong-Post Modified Thrie-Beam 7 Weak-Post W-Beam 9 Other non-proprietary guardrail 10 Aesthetic Barriers Type A Steel-Backed Timber Guardrail (with offset block) 1 Smooth Stone Masonry Guardwall 2 Other non-proprietary aesthetic barrier 3 Merritt Parkway Steel-Backed Timber Guiderail 4 Rough Stone Masonry Guardwall 4 Steel-Backed Timber Round Log Rail 6 Type B Steel-Backed Timber Guardrail (without offset block) 7 Deception Pass State Park Log Rail 8 Median Barriers Safety-Shape (New Jersey)  1 Strong-Post (Steel) W-Beam 2 F-Shape  3 Strong-Post (Wood) W-Beam 4 Constant Slope (Single-Slope) Barrier (TX & CA designs) 5 Strong-Post (Steel) Thrie-Beam 6 Strong-Post (Wood) Thrie-Beam 7 Low-Tension Cable (3-Strand) 8 Vertical Concrete Barrier 8 Strong-Post Modified Thrie-Beam 10 Weak-Post W-Beam 11 Weak-Post Box-Beam 11 Other non-proprietary median barrier 13 Median Barrier Connections Pin and Loop  1 Steel Dowel 2 Other non-proprietary connection 3 Grid-Slot 4 Vertical I-Beam 5 Plate Insert 6

6 Test Article Tested to MASH Prioritization from Survey Top T-Lock 6 Side Plates 8 Tongue and Groove 9 X-Bolt  10 Lap-Splice 10 Channel Splice 10 Bottom T-Lock 10 Transitions Box-Beam Box-Beam Guardrail to Permanent Concrete Barrier 1 Box-Beam Guardrail to F-Shape Concrete Barrier 1 Box-Beam Guardrail to Safety-Shape Concrete Barrier 3 Box-Beam Guardrail to Single-Slope Concrete Barrier 3 Modified Box-Beam Guardrail to 4-Rail Steel Bridge Rail 3 Other non-proprietary box-beam transition 3 Box-Beam Guardrail to Vertical Concrete Barrier 7 Thrie-Beam Thrie-Beam Guardrail to Concrete Parapet  1 Thrie-Beam Guardrail to Vertical Concrete Parapet 2 Other non-proprietary thrie-beam transition 3 Thrie-Beam Guardrail to Alaska Multi-State Bridge Rail 4 W-Beam W-Beam Guardrail to Safety-Shape Concrete Bridge Rail 1 W-Beam Guardrail to F-Shape Concrete Parapet 2 W-Beam Guardrail to Flared Concrete Bridge Parapet 3 Other non-proprietary W-beam transition 4 W-Beam Guardrail to Alaska Multi-State Bridge Rail 5 Aesthetic Steel-Backed Timber Guardrail to Straight Stone Masonry Guardwall 1 Steel-Backed Timber Guardrail to Curved Stone Masonry Guardwall 2 Other non-proprietary aesthetic barrier 2 Terminals Buried-in-Backslope Terminal 1 Other non-proprietary terminal 2 New York Cable Rail Terminal 3 Modified Eccentric Loader Terminal (MELT) 3 Eccentric Loader Terminal (ELT) 5 Crash Cushions Other non-proprietary crash cushion 1 Connecticut Impact Attenuation System (CIAS) 2 Narrow Connecticut Impact Attenuation System (NCIAS) 3

7 Test Article Tested to MASH Prioritization from Survey Breakaway Hardware Small Sign Supports Steel U-Channel 1 Perforated Square Steel Tube 2 Wood Post 3 Rectangular, Uni-Directional Slip Base 4 Triangular, Omni-Directional Slip Base 5 Thin-Walled Aluminum Pipe 6 Fiber Reinforced Plastic (FRP) Post (3”) 7 Other non-proprietary sign support 7 Steel U-Channel 3 lb/ft 1 2 ½ lb/ft 2 4 lb/ft 3 Perforated Square Steel Tube 2-inch 1 2 ½-inch 2 2 ¼-inch 3 1 ¾-inch 4 Wood Post 4-inch x 4-inch 1 Modified 6-inch x 6-inch (2, 2-inch diameter holes) 2 Modified 4-inch x 6-inch (2, 1 ½-inch diameter holes) 3 4-inch x 6-inch 4 Modified 6-inch x 8-inch (2, 3-inch diameter holes) 5 5-inch round 6 5-inch x 5-inch 7 Wood Post Species Southern Yellow Pine 1 Douglas Fir 2 Other species of wood post 3 Installation in Weak Soil Yes 1 No 2 Large Sign Supports Other 1 Dual, W6x12 2 Single, W12x45 3 Fuse Plates Yes 1 No 2 Configuration of Slip Base Rectangular, Uni-Directional 1

8 Test Article Tested to MASH Prioritization from Survey Triangular, Omni-Directional Texas 2 Other 3 Orientation of Slip Plates Level 1 Inclined 2 Other 3 Luminaire Supports Transformer Base 1 Slip Base 2 Other non-proprietary luminaire support 3

9 Table 2. Aggregate Ranking of Roadside Safety Hardware by Frequency of Use. Device Rank Precast CMB with Pin and Loop Connection 1 Strong-Post (Steel) W-Beam Guardrail 2 Strong-Post (Wood) W-Beam Guardrail 3 Transformer Base Luminaire Support 4 Safety-Shape (New Jersey) Median Barrier 5 Steel U-Channel Sign Support 6 Strong-Post (Steel) W-Beam Median Barrier 7 W-Beam Guardrail to Safety-Shape Concrete Bridge Rail Transition 8 F-Shape Median Barrier 9 Perforated Square Steel Tube Sign Support 10 Wood Post Sign Support 11 Slip Base Luminaire Support 12 Thrie-Beam Guardrail to Concrete Parapet Transition 13 Thrie-Beam Guardrail to Vertical Concrete Parapet Transition 14 Rectangular, Uni-Directional Slip Base Sign Support 15 Strong-Post (Wood) W-Beam Median Barrier 16 Strong-Post (Steel) Thrie-Beam Guardrail 17 Buried-in-Backslope Terminal 18 W-Beam Guardrail to F-Shape Concrete Parapet Transition 19 Triangular, Omni-Directional Slip Base Sign Support 20 Strong-Post (Wood) Thrie-Beam Guardrail 21 Constant Slope (Single-Slope) Barrier (TX & CA designs) Median Barrier 22 Low-Tension Cable (3-Strand) Guardrail 23 Strong-Post (Steel) Thrie-Beam Median Barrier 24 Strong-Post (Wood) Thrie-Beam Median Barrier 25 W-Beam Guardrail to Flared Concrete Bridge Parapet Transition 26 Other non-proprietary terminal 27 Low-Tension Cable (3-Strand) Median Barrier 28 Vertical Concrete Barrier Median Barrier 29 Midwest Guardrail System (MGS) Guardrail 30 Precast CMB with Steel Dowel Connection 31 New York Cable Rail Terminal 32 Modified Eccentric Loader Terminal (MELT) 33 Thin-Walled Aluminum Pipe Sign Support 34 Eccentric Loader Terminal (ELT) 35 Other non-proprietary thrie-beam transition 36 Strong-Post Modified Thrie-Beam Guardrail 37 Weak-Post Box-Beam Guardrail 38 Strong-Post Modified Thrie-Beam Median Barrier 39 Weak-Post W-Beam Guardrail 40

10 Device Rank Other non-proprietary guardrail 41 Other non-proprietary luminaire support 42 Type A Steel-Backed Timber Guardrail (with offset block) 43 Smooth Stone Masonry Guardwall 44 Other non-proprietary precast CMB connection 45 Weak-Post W-Beam Median Barrier 46 Weak-Post Box-Beam Median Barrier 46 Other non-proprietary aesthetic barrier 48 Thrie-Beam Guardrail to Alaska Multi-State Bridge Rail Transition 49 Other non-proprietary crash cushion 50 Other non-proprietary median barrier 51 Merritt Parkway Steel-Backed Timber Guiderail 52 Rough Stone Masonry Guardwall 52 Other non-proprietary W-beam transition 54 Precast CMB with Grid-Slot Connection 55 Box-Beam Guardrail to F-Shape Concrete Barrier Transition 56 Box-Beam Guardrail to Permanent Concrete Barrier Transition 57 Steel-Backed Timber Round Log Rail 58 Modified Box-Beam Guardrail to 4-Rail Steel Bridge Rail Transition 59 Precast CMB with Vertical I-Beam Connection 60 Other non-proprietary box-beam transition 61 Box-Beam Guardrail to Single-Slope Concrete Barrier Transition 62 Box-Beam Guardrail to Safety-Shape Concrete Barrier Transition 63 Steel-Backed Timber Guardrail to Straight Stone Masonry Guardwall Transition 64 W-Beam Guardrail to Alaska Multi-State Bridge Rail Transition 65 Precast CMB with Plate Insert Connection 65 Precast CMB with Top T-Lock Connection 65 Type B Steel-Backed Timber Guardrail (without offset block) 68 Other non-proprietary sign support 69 Other non-proprietary aesthetic transition 70 Fiber Reinforced Plastic (FRP) Post (3") Sign Support 70 Steel-Backed Timber Guardrail to Curved Stone Masonry Guardwall Transition 72 Connecticut Impact Attenuation System (CIAS) 73 Precast CMB with Side Plates Connection 74 Box-Beam Guardrail to Vertical Concrete Barrier Transition 75 Precast CMB with Tongue and Groove Connection 75 Precast CMB with X-Bolt Connection 77 Precast CMB with Lap-Splice Connection 77 Precast CMB with Channel Splice Connection 77 Precast CMB with Bottom T-Lock Connection 77 Narrow Connecticut Impact Attenuation System (NCIAS) 81 Deception Pass State Park Log Rail 82 Note: Devices with a tied rank had the exact number of responses for each answer category.

11 Once all of the survey responses were received, TTI researchers analyzed the information and determined those features which are most frequently used and would, therefore, potentially be highest priority for evaluation to the MASH criteria. The results of the survey were weighted by individual hardware item, ranked among the hardware category, and aggregately ranked across all categories. The survey responses were a series of five check boxes for each device to indicate associated percentages of use: [Never; Rarely (1-25 percent); Somewhat Frequently (26- 50 percent); Frequently (51-75 percent); and Very Frequently (76-100 percent)]. Each response was weighted based on frequency of use. A response of “Never” was not weighted. The remaining responses of Rarely, Somewhat Frequently, Frequently, and Very Frequently were given weights of 1, 2, 3, and 4, respectively. Table 1 illustrates a weighted prioritization of the hardware by category and shows hardware that has already had one test performed to the MASH test conditions. A weighted prioritization of the aggregate of all hardware is shown in Table 2. As identified from the survey, the top ten most frequently used safety hardware are: 1. Precast concrete median barrier using a pin and loop connection 2. Strong steel post W-beam guardrail 3. Strong wood post W-beam guardrail 4. Transformer base luminaire support 5. Concrete safety shape median barrier 6. Steel u-channel sign support 7. Strong steel post W-beam median guardrail 8. W-beam guardrail to safety shape concrete barrier transition 9. F-shape concrete median barrier 10. Perforated square steel tube sign support Of the above-listed safety hardware, the New Jersey Safety Shape concrete barrier, F-shape concrete barrier, and strong steel post W-beam guardrail have been tested to the most critical MASH condition.

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TRB’s National Cooperative Highway Research Program (NCHRP) Web-Only Document 157: Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report explores the process that was followed in developing NCHRP Research Results Digest (RRD) 349: Evaluation of Existing Roadside Safety Hardware Using Manual for Assessing Safety Hardware (MASH) Criteria.

NCHRP RRD 349 explores the safety performance of widely used non-proprietary roadside safety features by using MASH. Examples of features evaluated include longitudinal barriers (excluding bridge railings), terminals and crash cushions, transitions, and breakaway supports.

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