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MASH 2016 Cable Barrier Testing Matrices

Question
State SC
Description Text We are concerned that the 4 tables presented in MASH 2016 will result in products having different completed tests that get marketed as fully MASH 2016 compliant.

It does not appear that MASH 2016 requires cable barrier manufacturers to test every condition of all tables 2-2B through 2-2E. If this is the expectation, why are so many conditions repeated throughout the tables?

We recommend that tables 2-2B through 2-2E be consolidated into a single matrix of tests to ensure that all cable barrier products are at least held to the same testing criteria.

Use of Table 2-2D would seem to be the most appropriate in that a single cable can be placed throughout the 6:1 cross section.

Table 2-2B results in the concern that the ditch bottom would violate Roadside Design Guide Figure 3-6.


Table 2-2D could be augmented to allow testing from the high side of a 4:1 slope with placement of the cable 4’ beyond the shoulder break. This would allow installations of dual runs of cable on 4:1 slopes while not violating RDG Fig 3-6 since the ditch bottom would be shielded from either side.

We are concerned that the remaining tables 2-2C and 2-2E are too limiting in real world applications, and that products tested to these conditions may not perform as well in real world installations.

Has there been any discussion of consolidation of these tables within the MASH criteria? Are there any concerns that proprietary manufacturers may not test their products in every situation?


Thanks,
Keywords
  • Guardrail
Other Keywords Cable Barrier
Date July 23, 2018


Response
Response

I can understand the concern from a state standpoint. Obviously, it can be a maze of tests for you to wade through to determine to what level any given cable system has been evaluated and if it did so adequately.

 

MASH does require all of the tests in each table to be conducted. The various tables are needed to deal with specific systems that were desired by manufacturers and states. Thus, there are separate matrices for both the 4:1 and 6:1 ditches as well as placement anywhere in the ditch versus at a 4’ offset.

 

The basic parameters and purpose of the tests in each table are similar. However, the impact points and barrier placement may change to evaluate the critical scenario for that specific configuration. I don’t believe that a single matrix would be sufficient to cover all of the variable configurations that were required when we complied the matrix with TTI.

 

I can also understand the concern that the 0-4’ placement may not meet a state’s needs. However, no one has met the criteria for the placement of the cable system anywhere in either a 6:1 of 4:1 v-ditch at this time and it was desired by AASHTO and the manufacturers that a matrix be provided for the 0-4’ offset case.

 

We had discussions on the slope geometry of the ditch and the RDG guidance as well. However, some states use and wanted the option of 4:1 v-ditches. As such, it was included.

 

Let me know if that addresses your questions or if you want to discuss it further.

Date July 24, 2018


Response
Response

Thanks for the response, we greatly appreciate it.

 

We do have some follow-up comments/questions we are hoping you could address:

 

First of all we wanted to clarify that, for the generic high tension cable barrier MSWRF is developing, the plan is to ultimately run all eight of the tests in Table 2-2D (with tests 3-10/3-11 being performed first as voted on this year).  Then the system may possibly need to be modified, and all of the tests in table 2-2C will be ran, ultimately resulting in 2 potentially distinct systems.  Is this still accurate?  If so, I am guessing 3-10 and 3-11 may be reran in 2-2C based on whether the system is modified?

  

If a state is to infer that a product is appropriate to install based on real world geometry and select a version of the device based on the table it was tested to, then tests like 3-15, 3-16, and 3-18 in tables 2-2C and 2-2E become confusing since the cable in these tests is not located in the 0’-4’  offset from shoulder break. 

 

Tests 3-15, 3-16, and 3-18 will be required for a single barrier system offset 0’-4’, correct?  Yes  When a barrier is restricted to the 0’-4’ section, does this mean that it must remain in the 0’-4’ offset for its entire run, or are these tests implying that it may cross over the ditch and into the 0’-4’ offset of the other shoulder so long as a certain amount is present in the 0’-4’?  If the former is accurate, then would tests 3-15/3-16/3-18 have any relevance to when using 2-2C and 2-2E matrices?

  

The only exception we see listed for all of these tests is if the system is a double median barrier system, but the tables allow for single or double barrier systems.  The exception regarding ditch widths appears to only apply to test 3-15, and this test must still be ran if the system is to be approved used in anything other than V-ditches > 26’/24’, correct?

 

Thanks again for taking the time to respond to our questions, and hope you are having a good start to the new week.

Date July 25, 2018


Response
Response

We are happy to help you all out. These matrices are confusing due to the large number of potential configurations and the complexity of cable barriers.

 

Responses below in red.

 

Let me know if you need anything else.

_______________________________________________________________________________________________________

We do have some follow-up comments/questions we are hoping you could address:

 

First of all we wanted to clarify that, for the generic high tension cable barrier MSWRF is developing, the plan is to ultimately run all eight of the tests in Table 2-2D (with tests 3-10/3-11 being performed first as voted on this year).  Then the system may possibly need to be modified, and all of the tests in table 2-2C will be ran, ultimately resulting in 2 potentially distinct systems.  Is this still accurate?  If so, I am guessing 3-10 and 3-11 may be reran in 2-2C based on whether the system is modified?

 

The generic cable median barrier being developed through the Midwest Pooled Fund is focused on a system for use anywhere in a 6:1 V-ditch. The test matrix for that type of system is defined in Table 2-2D. We plan to conduct both a small car and pickup truck test (3-10 and 3-11) on the system as part of the Pooled Fund program for the upcoming year. We have not moved towards placement of the barrier at a 4’ offset in a 4:1 ditch at this time. Previously, there was desire in the Pooled Fund to develop a system for anywhere in a 4:1 v-ditch . However, that has been scaled back for now. To use the system designed for use anywhere in a 6:1 V-ditch at a 4’ offset in a 4:1 v-ditch, we would have to re-examine the design of the system after completion of the test matrix in 2-2D and see if the cable heights and system design chosen would work in that application. However, it may be that little to no modification is required as there is potential that the cable heights selected for use anywhere in a 6:1 V-ditch would still work for placement in a 4:1 v-ditch with a 4’ offset.  Depending on the level of modification needed, we would determine what tests in 2-2C would need to be rerun.

 

If a state is to infer that a product is appropriate to install based on real world geometry and select a version of the device based on the table it was tested to, then tests like 3-15, 3-16, and 3-18 in tables 2-2C and 2-2E become confusing since the cable in these tests is not located in the 0’-4’  offset from shoulder break. 

 

Tables 2-2C and 2-2E are for evaluation of median cable systems place at 0 ft – 4 ft offsets from a median v-ditch.

 

Test 3-15 is used to evaluate the potential for small car underride and is not required for systems placed at 0-4 ft offsets if they are used in ditches over a specified width. If the system is intended for use in narrower v-ditches, then the test must be run, but at the location used for cable systems used anywhere in a v-ditch. This point is the critical underride location in the respective ditches. As such a vehicle that does not underride at this point would not be expected to underride at the system’s typical 0-4 ft offset.

 

Test 3-16 evaluates the performance of the barrier for a small car traversing the v-ditch. As such, a critical offset from the backside SBP is specified that is critical in terms of vehicle capture and stability. For systems intended for use at a 0-4 ft offset from a 4:1 and 6:1 v-ditches, that critical point was determined to be 1 ft and 4 ft from the backside SBP, respectively. These points were based on computer simulation modeling done by MwRSF combined with data from other labs. Similar to test 3-15, evaluation at this critical offset would allow the use of the system at anywhere within the standard 0-4 ft offset for the barrier.

 

Test 3-18 evaluates the performance of the barrier for a pickup truck traversing the v-ditch. The logic behind this test is similar to that of test 3-15, but different placements were determined for the critical barrier placement based on computer modeling. Evaluation at this critical offset would allow the use of the system at anywhere within the standard 0-4 ft offset for the barrier.

 

Tests 3-15, 3-16, and 3-18 will be required for a single barrier system offset 0’-4’, correct?  Yes  When a barrier is restricted to the 0’-4’ section, does this mean that it must remain in the 0’-4’ offset for its entire run, or are these tests implying that it may cross over the ditch and into the 0’-4’ offset of the other shoulder so long as a certain amount is present in the 0’-4’?  If the former is accurate, then would tests 3-15/3-16/3-18 have any relevance to when using 2-2C and 2-2E matrices?

 

Conducting the matrices for 2-2C or 2-2E would not ensure the crashworthiness of the system in an area where it traversed the width of the ditch outside of the 0-4 ft offset. Thus, it would be recommended to leave the system at its 0-4 ft offset for the entire run or use a system for use anywhere in the ditch.

 

The only exception we see listed for all of these tests is if the system is a double median barrier system, but the tables allow for single or double barrier systems.  The exception regarding ditch widths appears to only apply to test 3-15, and this test must still be ran if the system is to be approved used in anything other than V-ditches > 26’/24’, correct?

 

Yes

Date July 27, 2018


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