Volume I: Evaluation of Existing Roadside Safety Hardware Using Updated Criteria—Technical Report (2010) / Chapter Skim
Currently Skimming:
Pages 12-88
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 12... ...
12 III. ASSESSMENT OF ROADSIDE SAFETY HARDWARE A limited number of full-scale crash tests were performed under NCHRP Project 22-14(02)
|
From page 13... ...
13 Table 3. Summary of Crash Tests Conducted under NCHRP Project 22-14(02)
|
From page 14... ...
14 Structural Adequacy In regard to longitudinal barrier impacts, structural adequacy is evaluated with respect to a barrier's ability to contain the impacting vehicle and either redirect it or capture it and bring it to a controlled stop. The vehicle is not permitted to penetrate, underride, or override the barrier although controlled lateral deflection is acceptable.
|
From page 15... ...
15 Data from two instrumented wall studies(32, 33) were used to derive barrier design loads for various test or performance levels included in the AASHTO LRFD Bridge Design Specifications: Section 13 – Railings.
|
From page 16... ...
16 vehicle length. Using measured vehicle lengths of test vehicles (from the front bumper to the C.G.)
|
From page 17... ...
17 when MASH Test 4-12 was conducted on a 32-inch tall New Jersey safety-shape concrete barrier (see Test 11 in Table 3) , the SUT rolled over the top of the barrier.
|
From page 18... ...
18 C.G. height than the 2000P, its SSF is actually greater than the 2000P.
|
From page 19... ...
19 the front, impact-side wheel at a joint, splice, or transition that results in the wheel being pushed into the fire wall and toe pan area of the occupant compartment. While such behavior was rarely observed when testing with large passenger sedans under NCHRP Report 230, the short front overhang of the pickup truck exposed the wheel and made snagging contact between the wheel and structural components of barriers a common occurrence.
|
From page 20... ...
20 Rating Extent of Intrusion Good <5.9 inches Acceptable 5.9 inches – 8.9 inches Marginal 8.9 inches – 11.8 inches Poor >11.8 inches MASH also makes a clear distinction between: "(a) penetration, in which a component of the test article actually penetrates into the occupant compartment; and (b)
|
From page 21... ...
21 Strong-Post W-Beam Guardrail [modified G4(1S)
|
From page 22... ...
22 These strong-post W-beam guardrail systems are at or near their performance limits under NCHRP Report 350 impact conditions. The increase in the weight of the proposed ½-ton, 4-door, pickup truck (designated 2270P)
|
From page 23... ...
23 Figure 3. Typical Cross-Section of Thrie-Beam Guardrail.
|
From page 24... ...
24 Modified Thrie-Beam Guardrail The modified thrie-beam guardrail system was originally developed by TTI researchers in the mid-1980s to contain buses(43)
|
From page 25... ...
25 the researchers recommend performing MASH test 4-12 on the modified thrie-beam guardrail system if a TL-4 guardrail system is desired. Weak-Post W-Beam Guardrail (G2)
|
From page 26... ...
26 The MASH 2270P test vehicle has demonstrated sensitivity to rail height. In addition, previous testing has shown that the impact performance of this system and other weak-post guardrail systems is sensitive to the post-to-rail attachment detail.
|
From page 27... ...
27 Presently, there are five proprietary high-tension cable barriers in the market place. All of these systems are proprietary and, thus, will not be discussed herein.
|
From page 28... ...
28 Figure 7. Typical Cross-Section of Weak-Post Box-Beam Guardrail System.
|
From page 29... ...
29 Additionally, Connecticut designed the Merritt Parkway wood guiderail and performed crash tests on it in accordance with NCHRP Report 350 under contract DTFH61-95-C-00119(48)
|
From page 30... ...
30 Figure 9. Type A Steel-Backed Timber Guardrail System.
|
From page 31... ...
31 Figure 10. Merritt Parkway Steel-Backed Timber Guardrail System.
|
From page 32... ...
32 Test Level 2 Type B Steel-Backed Timber Guardrail The Type B Steel-Backed Timber Guardrail is a semi-rigid rough sawn wood post and wood rail element barrier with a steel plate rail bolted to the rear of the wood rail guardrail. The Type A and Type B Steel-Backed Timber Guardrails only differ in the inclusion or omission of the wood blockout.
|
From page 33... ...
33 bolted to the rear of the wood rail guardrail. The wood used is typically either Southern Pine or Douglas Fir.
|
From page 34... ...
34 Preservation Office, and Washington State Parks and Recreation. The rail was developed to emulate the appearance of the original 1935 Civilian Conservation Corps (CCC)
|
From page 35... ...
35 Test Level 1 Glacier Park Removable Timber Guardrail The Glacier Park Removable Timber Guardrail is a semi-rigid removable rough-sawn wood rail and steel post barrier with a 4-inch tall x 6-inch deep concrete curb placed in front of the face of the barrier. This barrier was designed to be removed annually during the closed winter period of the park to prevent snow accumulation.
|
From page 36... ...
36 were very similar; test 1-10 was 0.28 inch and test 1-11 was 0.35 inch. The vehicle maximum roll and pitch angles were minor and the vehicle was very stable throughout both the 1-10 and 1-11 tests(47)
|
From page 37... ...
37 tests(47)
|
From page 38... ...
38 Test Level 5 (TL-5) • 42-inch tall Safety Shape (New Jersey)
|
From page 39... ...
39 Figure 16. Typical Cross-Section of a Low-Tension Cable Median Barrier System.
|
From page 40... ...
40 dimensions, reinforcing, and foundation details are equivalent to the other barrier designs that have been successfully tested(5)
|
From page 41... ...
41 Figure 18. Typical Cross-Section of F-Shape Concrete Safety Barrier.
|
From page 42... ...
42 Given the estimated impact force associated with MASH test 3-11 with the new pickup truck is comparable to the design impact force used for NCHRP Report 350 test 3-11, the New Jersey, F-shape, constant- or single-slope barrier, vertical wall, and the Ontario tall wall barrier should all easily meet the structural adequacy requirements for the MASH Test Level 3 (TL-3) impact conditions.
|
From page 43... ...
43 MASH test 3-10 was conducted on a permanent New Jersey profile barrier under NCHRP Project 22-14(02) to investigate this impact performance concern (see Test 8 of Table 3)
|
From page 44... ...
44 Portable and Precast Concrete Median Barrier Portable and precast concrete median barriers are often used in work zones to shield motorists from hazards in the work area (e.g., pavement edge drops, excavations, equipment, etc.) , provide positive protection for workers, and separate two-way traffic.
|
From page 45... ...
45 Figure 20. Typical Cross-Section of Low-Profile Barrier Segment.
|
From page 46... ...
46 For these reasons, it is the opinion of the researchers that the low-profile barrier system should be able to successfully redirect the new pickup under TL-2 impact conditions. However, this assertion may ultimately have to be demonstrated through full-scale crash testing.
|
From page 47... ...
47 Table 5. FHWA Accepted Temporary Concrete Median Barriers with Pin Connection FHWA Approval Letter Agency/ Manufacturer Barrier Profile Segment Length (ft)
|
From page 48... ...
48 Table 6. FHWA Accepted Temporary Concrete Median Barriers with Miscellaneous Connections FHWA Approval Letter Agency/ Manufacturer Barrier Profile Segment Length (ft)
|
From page 49... ...
49 F-Shape Type X Connection As is noted in Table 6, the most recently developed portable concrete barrier connection and also the lowest deflection connection type is the TxDOT F-shape Type X or "cross-bolted" connection. The Type X connection utilizes two threaded rods/bolts to form the connection.
|
From page 50... ...
50 Figure 21. F-Shape Concrete Safety Barrier with X-Bolt Connection.
|
From page 51... ...
51 the F-shape barriers with Type X connections for impacts with the small car under MASH test 3-10 impact conditions will be small. Therefore, both F-shape barriers with Type X connections should meet the impact performance requirements for MASH test 3-10.
|
From page 52... ...
52 rail or curb. However, this was not always a definitive solution.
|
From page 53... ...
53 Table 7. Summary of NCHRP Report 350 Transition Tests Description Rail Rubrail Top Height of Rail (inch)
|
From page 54... ...
54 Description Rail Rubrail Top Height of Rail (inch) Posts Post Spacing (inch)
|
From page 55... ...
55 Description Rail Rubrail Top Height of Rail (inch) Posts Post Spacing (inch)
|
From page 56... ...
56 Description Rail Rubrail Top Height of Rail (inch) Posts Post Spacing (inch)
|
From page 57... ...
57 Description Rail Rubrail Top Height of Rail (inch) Posts Post Spacing (inch)
|
From page 58... ...
58 Description Rail Rubrail Top Height of Rail (inch) Posts Post Spacing (inch)
|
From page 59... ...
59 Figure 22. Elevation of Texas TL-3 Guardrail-to-Concrete Bridge Rail Transition.
|
From page 60... ...
60 For these reasons, TxDOT developed a cost-effective TL-2 transition for use on low-speed roadways. The TL-2 transition, shown in Figure 23, is entirely comprised of standard hardware components and is significantly less expensive and complex to install than the high-speed, TL-3 transition system.
|
From page 61... ...
61 pickup truck of NCHRP Report 350 than the 1/2-ton, 4-door pickup truck designated in MASH. Although the 13 percent increase in vehicle weight and impact severity may slightly increase dynamic deflections, increases, if any, in vehicle roll angles and occupant compartment deformations resulting from NCHRP Report 350 test 3-21 should be minimal.
|
From page 62... ...
62 End Terminals Test Level 3 Guardrail Terminals Buried-in-Backslope Guardrail Terminal (G4 System Guardrail)
|
From page 63... ...
63 As noted in FHWA acceptance letter CC53A(17) : Key elements common to all buried-in-backslope include: 1)
|
From page 64... ...
64 Figure 25. Eccentric Loader Terminal.
|
From page 65... ...
65 ELT to the MASH conditions. The probability of the ELT performing successfully to the MASH conditions is low and the terminal has seen only limited use.
|
From page 66... ...
66 Test Level 2 Guardrail Terminals Vermont Low-Speed Strong Post W-Beam Guardrail Terminal – (G-1d)
|
From page 67... ...
67 Upon successful completion of the 1-30, Vermont DOT decided to evaluate the terminal to NCHRP Report 350 TL-2. In test 2-30 (end-on impact)
|
From page 68... ...
68 length. The second 12 ft-6 inch section of W-beam is shop bent to a radius of 90 ft over its entire length.
|
From page 69... ...
69 MELT should perform satisfactorily to the MASH conditions for Test Level 2. However, the researchers give this terminal a low priority for testing to the MASH conditions given the limited number of states that currently use the MELT.
|
From page 70... ...
70 To evaluate the CIAS in accordance with NCHRP Report 350, two crash tests were initially performed, 3-32 and 3-38(64)
|
From page 71... ...
71 believe there is a low probability the CIAS will satisfy the MASH evaluation criteria as currently designed. Narrow Connecticut Impact Attenuator System The Narrow Connecticut Impact Attenuator System (NCIAS)
|
From page 72... ...
72 In test 3-32, an 1808-lb passenger car traveling 61.5 mi/h impacted the nose of the NCIAS at 14.4 degrees and deformed the cushion 12.9 ft. The vehicle yawed 109 degrees and came to rest 14.8 ft laterally from the cushion.
|
From page 73... ...
73 research program to develop a bullnose terminal that would meet the safety performance evaluation criteria of NCHRP Report 350(68-70)
|
From page 74... ...
74 terminal system. The highest 10-msec longitudinal occupant ridedown acceleration was 9.2 Gs and the change in the longitudinal occupant impact velocity was 17.7 ft/s.
|
From page 75... ...
75 high speed test. For TL-3, the relevant test designations are 3-60 and 3-61, which have design impact speeds of 21.8 mi/h and 62.2 mi/h, respectively.
|
From page 76... ...
76 document came additional performance evaluation criteria for small sign supports and luminaires. In general, deformation to the occupant compartment in the area of the roof could not exceed 6 inches.
|
From page 77... ...
77 Table 8. Summary of FHWA-Accepted Breakaway Hardware.
|
From page 78... ...
78 Flexible/Bending Sign Support Fracturing Sign Support Controlled Release Sign Support Cast Aluminum Luminaire Support Figure 32. Sign Support and Luminaire Bases.
|
From page 79... ...
79 Flexible/bending supports may or may not ultimately release from their mounted position. If the support yields to the vehicle in crash testing by pulling completely out of the soil, careful attention should be paid when changing the founding method of anchoring the sign installation.
|
From page 80... ...
80 level of windshield damage associated with some breakaway supports accepted under NCHRP Report 350 may not meet the more stringent criteria adopted in MASH. Further, careful consideration should be given to two new impact criteria in MASH, 1)
|
From page 81... ...
81 Figure 33. Photographs of Wedge Anchor Sign Support.
|
From page 82... ...
82 Figure 34. Details of Wedge Anchor Sign Support.
|
From page 83... ...
83 Summary of Wedge Anchor Test Results The wedge anchor sign support system demonstrated satisfactory impact performance. The sign support activated by yielding to the impacting vehicle and then pulling out of its socket.
|
From page 84... ...
84 Figure 35. Vehicle/Installation Geometrics for Wedge Anchor & Triangular Slip Base Test.
|
From page 85... ...
85 Texas Triangular Slip Base There are two variations of the Texas triangular slip base sign support system. One version uses a 10 BWG galvanized steel tube as the vertical support and can accommodate sign panels up to 16 ft2 in area.
|
From page 86... ...
86 Figure 36. Photographs of Texas Triangular Slip Base.
|
From page 87... ...
87 Figure 37. Details of the Texas Triangular Slip Base.
|
From page 88... ...
88 Summary of Texas Slip Base Test Results The triangular slip base sign support system demonstrated satisfactory impact performance when evaluated in accordance with MASH criteria. The slip base mechanism activated as designed.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.