National Academies Press: OpenBook
« Previous: III. Assessment of Roadside Safety Hardware
Page 89
Suggested Citation:"IV. Crash Testing Matrix and Evaluation Plan ." 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 89
Page 90
Suggested Citation:"IV. Crash Testing Matrix and Evaluation Plan ." 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 90
Page 91
Suggested Citation:"IV. Crash Testing Matrix and Evaluation Plan ." 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 91
Page 92
Suggested Citation:"IV. Crash Testing Matrix and Evaluation Plan ." 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 92
Page 93
Suggested Citation:"IV. Crash Testing Matrix and Evaluation Plan ." 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 93
Page 94
Suggested Citation:"IV. Crash Testing Matrix and Evaluation Plan ." 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 94
Page 95
Suggested Citation:"IV. Crash Testing Matrix and Evaluation Plan ." 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 95
Page 96
Suggested Citation:"IV. Crash Testing Matrix and Evaluation Plan ." 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 96
Page 97
Suggested Citation:"IV. Crash Testing Matrix and Evaluation Plan ." 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 97
Page 98
Suggested Citation:"IV. Crash Testing Matrix and Evaluation Plan ." 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 98

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

89 IV. CRASH TESTING MATRIX AND EVALUATION PLAN In review, TTI researchers surveyed the State DOTs for use and frequency rates for non-proprietary hardware; and reviewed the test reports of the crash tests performed under NCHRP Project 22-14(02), TxDOT project FHWA/TX-07/0-5526-1, and other NCHRP Report 350 crash tests performed. In the performance of these tasks, a weighted ranking of highway roadside safety hardware categorized by device type was presented in Table 1. An aggregate ranking of highway roadside safety hardware by frequency of use was performed for all categories and presented in Table 2. Table 3 presented the crash tests performed in NCHRP Project 22-14(02). The researchers compiled the aforementioned information and developed a suggested crash testing matrix with an assigned probability of passing the MASH testing and evaluation criteria. Table 9 shows the compiled data from Tables 1 through 3 and provides a probability of the device meeting the evaluation criteria if tested and evaluated to MASH. In lieu of assigning a numerical value to the probability of any particular piece of hardware passing or failing a crash test, a qualitative measure of “poor”, “fair”, “good”, and “excellent” is used to indicate the hardware’s projected ability to meet the MASH test level that the device currently satisfies under NCHRP Report 350. In addition to the material presented in Table 9, the top ten most frequently used roadside safety hardware were identified previously in Table 2. Of the top ten identified, 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 conditions. Expanding this list further to include the top 25 prioritized roadside safety hardware yielded the following: 1. Precast concrete median barrier using a pin and Tested loop (P&L) connection 2. Strong steel post W-beam guardrail Tested 3. Strong wood post W-beam guardrail Testing not considered necessary 4. Transformer base luminaire support 5. Concrete safety shape median barrier Tested 6. Steel u-channel sign support – 3 lb/ft 7. Strong steel post W-beam median guardrail Testing not considered necessary 8. W-beam guardrail to safety shape concrete barrier transition 9. F-shape concrete median barrier Tested in temporary (P&L) configuration 10. Perforated square steel tube sign support – 2 inch

90 Table 9. Compiled Prioritization, Ranking, and Probability for Successfully Complying with MASH Criteria. Test Article Discussion in Report Tested to MASH Prioritization to Survey Aggregate Ranking Probability of Passing MASH Guardrails Pg 20-28 Strong-Post (Steel) W-Beam Pg 21  1 2 N/A Strong-Post (Wood) W-Beam Pg 21&111 * 2 3 N/A* Strong-Post (Steel) Thrie-Beam Pg 22&165 3 17 Good Strong-Post (Wood) Thrie-Beam Pg 23 4 21 Good Low-Tension Cable (3-Strand) Pg 26 5 23 Good Midwest Guardrail System (MGS) Pg 22  6 30 N/A Weak-Post Box-Beam Pg 27&151 7 38 Good Strong-Post Modified Thrie-Beam Pg 24 7 37 Excellent Weak-Post W-Beam Pg 25&158 9 40 Fair – Good Other non-proprietary guardrail 10 41 N/A Aesthetic Barriers Pg 28-37 Type A Steel-Backed Timber Guardrail (with offset block) Pg 29 1 43 Good Smooth Stone Masonry Guardwall 2 44 Good Other non-proprietary aesthetic barrier Pg 28 3 48 Good Merritt Parkway Steel-Backed Timber Guiderail Pg 30 4 52 Good Rough Stone Masonry Guardwall Pg 29 4 52 Good Steel-Backed Timber Round Log Rail Pg 32 6 58 Good Type B Steel-Backed Timber Guardrail (without offset block) Pg 32 7 68 Good Deception Pass State Park Log Rail Pg 33 8 82 Good Median Barriers Pg 37-46 Safety-Shape (New Jersey) Pg 39&99  1 5 N/A – TL-3 Strong-Post (Steel) W-Beam Pg 37&118 * 2 7 N/A* F-Shape Pg 39  3 9 N/A Strong-Post (Wood) W-Beam Pg 37 * 4 16 N/A* Constant Slope (Single-Slope) Barrier (TX & CA designs) Pg 39 * 5 22 N/A* Strong-Post (Steel) Thrie-Beam Pg 37 6 24 Good

91 Test Article Discussion in Report Tested to MASH Prioritization to Survey Aggregate Ranking Probability of Passing MASH Median Barriers (continued) Strong-Post (Wood) Thrie-Beam Pg 37 7 25 Good Low-Tension Cable (3-Strand) Pg 38 8 28 Good Vertical Concrete Barrier Pg 39 * 8 29 N/A* Strong-Post Modified Thrie-Beam Pg 37 10 39 Excellent Weak-Post W-Beam Pg 37 11 46 Fair – Good Weak-Post Box-Beam Pg 37 11 46 Good Other non-proprietary median barrier Pg 44 13 51 System Dependent Median Barrier Connections Pg 46-51 Pin and Loop Pg 47  1 1 N/A Steel Dowel Pg 47 2 31 Fair – Good Other non-proprietary connection Pg 47 & 51 3 45 System Dependent Grid-Slot Pg 48 4 55 Fair – Good Vertical I-Beam Pg 48 5 60 Good Plate Insert Pg 48 6 65 Fair – Good Top T-Lock Pg 48 6 65 Good Side Plates Pg 48 8 74 Good Tongue and Groove Pg 48 9 75 Good X-Bolt Pg 48&49  10 77 N/A Lap-Splice Pg 48 10 77 Good Channel Splice Pg 48 10 77 Good Bottom T-Lock Pg 48 10 77 Good Transitions Pg 51-61 Box-Beam Box-Beam Guardrail to Permanent Concrete Barrier Pg53 1 57 Good Box-Beam Guardrail to F-Shape Concrete Barrier Pg53 1 56 Good Box-Beam Guardrail to Safety-Shape Concrete Barrier Pg53 3 63 Good Box-Beam Guardrail to Single-Slope Concrete Barrier Pg53 3 62 Good Modified Box-Beam Guardrail to 4-Rail Steel Bridge Rail Pg53 3 59 Good

92 Test Article Discussion in Report Tested to MASH Prioritization to Survey Aggregate Ranking Probability of Passing MASH Transitions (continued) Other non-proprietary box-beam transition 3 61 System Dependent Box-Beam Guardrail to Vertical Concrete Barrier Pg53 7 75 Good Thrie-Beam Pg 53 Thrie-Beam Guardrail to Concrete Parapet Pg 53  1 13 N/A Thrie-Beam Guardrail to Vertical Concrete Parapet Pg 53 2 14 Excellent Other non-proprietary thrie-beam transition Pg 53 3 36 Good – Excellent Thrie-Beam Guardrail to Alaska Multi-State Bridge Rail Pg 53 4 49 Good W-Beam Pg 56 W-Beam Guardrail to Safety-Shape Concrete Bridge Rail Pg 56 1 8 Good W-Beam Guardrail to F-Shape Concrete Parapet Pg 56 2 19 Good W-Beam Guardrail to Flared Concrete Bridge Parapet Pg 56&130 3 26 Good Other non-proprietary W-beam transition Pg 56 4 54 Good W-Beam Guardrail to Alaska Multi-State Bridge Rail Pg 56 5 65 Good Aesthetic Pg 58 Steel-Backed Timber Guardrail to Straight Stone Masonry Guardwall Pg 58 1 64 Good Steel-Backed Timber Guardrail to Curved Stone Masonry Guardwall Pg 58 2 70 Good Other non-proprietary aesthetic barrier Pg 58 2 72 Good Terminals Pg 61-69 Buried-in-Backslope Terminal Pg 62 1 18 Good Other non-proprietary terminal Pg 66 2 27 System Dependent New York Cable Rail Terminal Pg 65 3 32 Good Modified Eccentric Loader Terminal (MELT) Pg 67 3 33 Poor Eccentric Loader Terminal (ELT) Pg 63 5 35 Poor Crash Cushions Pg 69-74 Other non-proprietary crash cushion Pg 72 1 50 System Dependent

93 Test Article Discussion in Report Tested to MASH Prioritization to Survey Aggregate Ranking Probability of Passing MASH Crash Cushions (continued) Connecticut Impact Attenuation System (CIAS) Pg 69 2 73 Poor – Fair Narrow Connecticut Impact Attenuation System (NCIAS) Pg 71 3 81 Poor – Fair Breakaway Hardware Pg 74-88 Small Sign Supports Pg 77 Steel U-Channel Pg 77&138 1 6 Good Perforated Square Steel Tube Pg 77&139 2 10 Good Wood Post 3 11 Good Rectangular, Uni-Directional Slip Base 4 15 Good Triangular, Omni-Directional Slip Base 5 20 Good Thin-Walled Aluminum Pipe 6 34 Good Fiber Reinforced Plastic (FRP) Post (3”) 7 70 Good Other non-proprietary sign support 7 69 System Dependent 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

94 Test Article Discussion in Report Tested to MASH Prioritization to Survey Aggregate Ranking Probability of Passing MASH 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 Pg 77 Other 1 Dual, W6x12 2 Single, W12x45 3 Fuse Plates Yes 1 No 2 Configuration of Slip Base Rectangular, Uni-Directional 1 Triangular, Omni-Directional Pg 85 Texas 2 N/A – Excellent Other 3 Orientation of Slip Plates Level 1 Inclined 2 Other 3 Luminaire Supports Transformer Base 1 4 Good Slip Base 2 12 Good Other non-proprietary luminaire support 3 42 System Dependent *Prior testing of similar hardware will likely satisfy the testing requirements for this device and no additional testing would be required.

95 11. Wood Post Sign Support – 4 inch x 4 inch 12. Slip Base Luminaire Support 13. Thrie-Beam Guardrail to Concrete Parapet Transition Tested 14. Thrie-Beam Guardrail to Vertical Concrete Parapet Transition 15. Rectangular, Uni-Directional Slip Base Sign Support 16. Strong-Post (Wood) W-Beam Median Barrier Testing not considered necessary 17. Strong-Post (Steel) Thrie-Beam Guardrail 18. Buried-in-Backslope Terminal 19. W-Beam Guardrail to F-Shape Concrete Parapet Transition 20. Triangular, Omni-Directional Slip Base Sign Support 21. Strong-Post (Wood) Thrie Beam Guardrail 22. Constant Slope (Single-Slope) Barrier Testing not (TX & CA designs) Median Barrier considered necessary 23. Low-Tension Cable (3-Strand) Guardrail 24. Strong-Post (Steel) Thrie Beam Median Barrier 25. Strong-Post (Wood) Thrie Beam Median Barrier The above devices that are struck out were either tested during the conduct of NCHRP Project 22-14(02) or the researchers believe that one of those tests will suffice as evidence of a similar device satisfying the MASH criteria without performing additional test(s). Additionally, examination of the above list yields a few distinct categories of devices that may be summarized in groups. A discussion of these hardware groups follows. SMALL SIGN SUPPORTS AND LUMINAIRE BASES Summarizing the above list by device category, it can be readily seen that seven of the roadside safety hardware items listed are small sign supports and luminaire bases. The small sign supports identified represent the vast majority of supports used by state and local transportation agencies. It also represents the hardware type most overlooked during the evaluation process when NCHRP Report 350 was adopted and the large passenger vehicle was changed to the pickup truck. Crash test experience with the 2000P or the 2270P vehicle is almost non-existent with these devices and should be addressed with regard to the potential for the sign panel and/or support to deform the roof and windshield.

96 THRIE-BEAM LONGITUDINAL BARRIER Four of the safety hardware devices ranked above are thrie-beam longitudinal barriers; wood and steel post, roadside and median barrier guardrail. In addition, a thrie-beam guardrail transition to a vertical concrete parapet is listed. The researchers would recommend giving high-priority to testing the modified thrie-beam guardrail to TL-4 using the MASH 10000S vehicle. Depending on the fabrication details, the thrie-beam to safety shape concrete barrier transition test previously performed in NCHRP Project 22-14(02) may suffice for an appropriately designed vertical concrete parapet. W-BEAM TRANSITIONS TO SAFETY AND F-SHAPE BARRIER Two of the above ranked safety hardware devices are W-beam guardrail transitions to safety and F-shape barriers. Successful transition designs proved very challenging during the adoption of NCHRP Report 350. Many W-beam to concrete parapet transition designs were found to perform inadequately with regard to vehicle stability and/or occupant compartment deformation when crash tested. It is anticipated that the NCHRP Report 350 designed W-beam transitions will perform acceptably when evaluated to the MASH conditions. The occupant compartment deformation evaluation criteria have been relaxed from NCHRP Report 350 and the MASH 2270P test vehicle is a more stable test vehicle platform. However, the affect of the 13 percent increase in kinetic energy for the 2270P vehicle has not been evaluated on a W-beam transition and warrants consideration when developing the test matrix for this project. BURIED-IN-BACKSLOPE TERMINAL The buried-in-back slope terminal is the most predominately used terminal for aesthetic guardrails such as the steel-backed timber rail. In addition, many states use it where the edge of the right-of-way and/or roadside backslopes are close to the travel way. The buried-in-backslope type of terminal has proven to be a safe and cost-effective means of terminating a guardrail installation. However, the researchers have concern regarding the performance of this terminal in regard to MASH due to the increase in the impact angle to 25 degrees for the beginning of length of need test with the pickup. It is recommended that testing of this terminal in the W-beam and steel-backed timber configuration with the 2270P vehicle be considered. CABLE GUARDRAIL Low-tension cable (strand) guardrail ranked number 23 in the list of hardware to be tested out of 25. The low-tension guardrail has a high probability of performing well to MASH on slopes of 10:1 or flatter. However, deflections will likely increase marginally due to the increase in weight of the 2270P test vehicle. The widespread use of this barrier in several states may warrant test consideration. However, it should be noted that a high-tension, non-proprietary cable guardrail is currently under development by the Midwest States Regional Pooled Fund program. The Pooled Fund cable system, when completed, will be tested to the MASH

97 conditions and should be capable of being installed on slopes of 4:1 or flatter. This new system may negate the need to test the 3-rope, low-tension cable guardrail system. OTHER GUARDRAILS Although the weak-post W-beam and weak-post box beam guardrails were not ranked in the top 25 hardware devices based on the survey, they both warrant some consideration for testing under this project. The weak-post box beam ranked 38, while the weak-post W-beam ranked 40. These guardrails are widely used in a few states and provide alternatives to the strong-post guardrail systems. Both systems have a “good” probability of passing the testing and evaluation criteria of MASH. SUMMARY The researchers reviewed a total of 90 different types or configurations of non- proprietary roadside safety hardware. Of the initial top 25 prioritized roadside safety hardware devices, 16 remained under consideration for testing and evaluation to MASH after eliminating those that had been previously tested or were considered to be equivalent to systems already tested. During the review process, the researchers noted that G3 box-beam guardrail, modified G2 weak-post W-beam guardrail, and G9 thrie-beam guardrail ranked relatively low in the survey (numbers 37, 38, and 40, respectively). Despite their low ranking, it was noted that they are used very extensively in some states. Therefore, the researchers elected to add G3 box-beam guardrail, modified G2 weak-post W-beam guardrail, and G9 thrie-beam guardrail to the list of hardware devices presented to the project panel for consideration of testing and evaluation to MASH. The NCHRP panel reviewed the researchers’ recommended top 19 prioritized roadside safety hardware items. After discussions between the NCHRP panel members and the researchers, the panel members decided the G4(2W) W-beam guardrail and the G4(1S) median barrier (ranked number 3 and 16, respectively) warranted evaluation and testing to MASH. Historically, both of these systems received acceptance based on a successful test of the “more critical” G4(1S) guardrail system. However, given the marginal performance of the G4(1S) guardrail system when tested under NCHRP study 22-14(02), the panel decided that these assumptions should be verified through testing. Test 3-11 was requested by the NCHRP panel for the G4(2W) guardrail to assess its performance equivalency to the modified G4(1S) guardrail. The additional constraint of the posts imposed by the double-sided G4(1S) W-beam median barrier raised concerns regarding barrier override by the 2270P and excessive occupant risk when impacted by the small passenger vehicle (1100C). The added post constraint delays release of the post from the rail, which can potentially result in vehicle climb and vaulting due to a localized drop in rail height. The delayed post release can also result in more severe wheel- post interaction and a higher level of occupant risk during the small car impact. Thus, both Test 3-10 and 3-11 were programmed for this median barrier system.

98 In addition, the panel wished to complete the evaluation of the 32 inch permanent New Jersey shape barrier (ranked number 5). Given its widespread use by the States, a complete and up-to-date evaluation was warranted. The permanent New Jersey shape barrier was tested under NCHRP study 22-14(02) with the 1100C passenger car (test 3-10). A test with the 2270P pickup truck (test 3-11) would complete the test matrix. Further, previous testing has shown that the New Jersey profile is a more critical shape than the F-shape or single slope profiles in terms of vehicle climb and instability. Therefore, a successful test sequence on the New Jersey profile would assert that the F-shape and single slope concrete barriers are also MASH compliant. The panel members re-ranked the list of highway safety hardware prioritized by the survey and expanded by the researchers to establish the final test matrix. As determined by the NCHRP panel in consultation with the researchers, the final test matrix for this study is shown below in priority order: 1. 32 inch permanent concrete New Jersey safety shape median barrier 2. G4(2W) W-beam guardrail 3. G4(1S) W-Beam Median Barrier 4. W-beam guardrail to safety shape concrete barrier transition – Pennsylvania design 5. Steel u-channel sign support – 4 lb/ft 6. Perforated square steel tube sign support – 2 inch 7. G3 Box beam guardrail 8. Modified G2 W-beam guardrail 9. G9 Thrie Beam Guardrail *Note: The steel u-channel sign support and perforated square steel tube sign support were ranked equivalently. Furthermore, for the pickup truck tests on the longitudinal barriers and transitions, the NCHRP project panel requested a 2007 Chevrolet Silverado be used, instead of the MASH Dodge 1500 Quad-Cab pickup, to assist with the validation of a finite element model of a 2007 Chevrolet Silverado pickup developed at the National Crash Analysis Center (NCAC) under the sponsorship of FHWA and NHTSA. The Dodge 1500 Quad-Cab pickup was used in the pickup truck test on the sign supports.

Next: V. Full-Scale Crash Testing »
Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report Get This Book
×
 Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

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.

READ FREE ONLINE

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!