Testing of Midwest Guardrail Systems with Reduced Post Spacing for MASH Compliance (610211-01)

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Problem Statement

The American Association of State Highway and Transportation Officials (AASHTO) and the Federal Highway Administration (FHWA) developed and adopted a joint implementation agreement that establishes compliance dates for use of the Manual for Assessing Safety Hardware (MASH) compliant hardware for new installations and full replacements on the National Highway System (NHS) that differ by hardware category. These compliance dates, as outlined in the implementation plan, are as follows:

  • December 31, 2017: W-beam barriers and cast-in-place concrete barriers;
  • June 30, 2018: W-beam terminals;
  • December 31, 2018: cable barriers, cable barrier terminals, and crash cushions;
  • December 31, 2019: bridge rails, transitions, all other longitudinal barriers (including portable barriers installed permanently), all other terminals, sign supports, and all other breakaway hardware.

To ensure compliance with the implementation deadlines, the Roadside Safety Pooled Fund has prioritized their testing needs of various barrier systems. For this project, Midwest Guardrail Systems (MGS) with reduced post spacing are desired to be tested. These systems are used when State Departments of Transportation (DOT) choose enhanced protection from a roadside hazard. Therefore, TTI was tasked to test these reduced post spacing systems for MASH compliance.

Objective

The objective of this study is to test MGS systems with reduced post spacing for MASH compliance.

Benefits

This project will benefit the members of the Roadside Safety Pooled Fund by helping them achieve MASH implementation in accordance with the adopted AASHTO/FHWA MASH Implementation Plan. MASH compliant MGS with reduced post spacing will provide the members of the Roadside Safety Pooled Fund with a valuable option for enhanced protection against roadside hazards.

Products

The TTI research team will prepare and submit a research report fully documenting all of the work completed within this project. Application documentation for FHWA Eligibility Letters will be provided for systems that meet FHWA Eligibility Letter requirements. For other systems, the research team will provide engineering justification explaining that the critical tests were performed.

Implementation

With successful crash test results, the Roadside Safety Pooled Fund will have MASH compliant systems that can be implemented when roadside hazards require enhanced protection.

Work Plan

The work plan for this project will consist of five tasks. The first task is titled MASH 3-10 Test of MGS with Quarter Post Spacing. The second task is titled MASH 3-11 Test of MGS with Quarter Post Spacing. The third task is titled MASH 3-11 Test of MGS with Half Post Spacing. The fourth task is titled MASH 3-11 Test of MGS with Transition Between Varying Post Spacings. The fifth task is titled Evaluation and Reporting.

Figure 1 below shows a section view of a typical MGS post with blockout and rail. A similar design will be used for the installations constructed during this project. However, not all the posts will be bolted to the guardrail. During the installation process of a MGS with quarter post spacing, not all posts will align with slots punched in the rail. To prevent end users from ordering special rails with extra slots punched out, the system will be tested without attaching the posts to the guardrail where no slots in the guardrail exist. The TTI research team believes this system will still behave well despite the lack of posts not having a connection to the rail element.

Figure 1. Section View of Typical MGS Installation.

The MGS was originally intended to move the splices away from the posts to improve the performance of the system during an impact. However, the MGS with half post spacing will have posts located at the splices between two rails. Because of the original intent of the MGS, the researchers suggest to also not attach the guardrail to the posts which align with a splice between two rails. The TTI research team anticipates that this will not negatively affect the results of the test.

Lastly, the installations for this project will use a non-nested system. Using a nested rail element creates significant difficulty during the installation process. Oftentimes, the installers will need to enlarge the slot in the rail to allow for the nested system to bolt to the post. Furthermore, the TTI research team believes the additional rail beam in nested systems only provide a slight improvement in performance, which does not outweigh the difficulties associated with installation. To prevent nested rail elements from becoming a necessity with reduced post spacing systems, the installations tested during this project will include non-nested rail elements.

Task 1: MASH 3-10 Test of MGS with Quarter Post Spacing

The TTI research team will perform a MASH 3-10 test on a MGS with quarter post spacing. The MASH 1100C (2420 lbs) small passenger car will impact the MGS with quarter post spacing at a speed of 62 mph and an angle of 25°. This test will evaluate the performance of a MGS with quarter post spacing upon impact with the 1100C small passenger car.

Task 2: MASH 3-11 Test of MGS with Quarter Post Spacing

The TTI research team will complete a full-scale MASH 3-11 test on a MGS with quarter post spacing. The MASH 2270P (5000 lbs) pickup truck will impact the MGS with quarter post spacing at a speed of 62 mph and an angle of 25°. This test will evaluate the performance of a MGS with quarter post spacing upon impact with the 2270P pickup truck.

Task 3: MASH 3-11 Test of MGS with Half Post Spacing

The TTI research team will complete a full-scale MASH 3-11 test on a MGS with half post spacing. The MASH 2270P (5000 lbs) pickup truck will impact the MGS with half post spacing at a speed of 62 mph and an angle of 25°. This test will evaluate the performance of a MGS with half post spacing upon impact with the 2270P pickup truck.

Task 4: MASH 3-11 Test of MGS with Transition Between Varying Post Spacings

The TTI research team will complete a full-scale MASH 3-11 test on a transition between full to quarter post spacing on a MGS. The MASH 2270P (5000 lbs) pickup truck will impact the transition between varying post spacings at a speed of 62 mph and an angle of 25°. This test will evaluate the performance of the transition between varying post spacings upon impact with the 2270P pickup truck.

Task 5: Evaluation and Reporting

The TTI research team will prepare a research report fully documenting the testing and evaluation of the four crash tests completed in this project. The report will include detailed engineering drawings of the reduced post spacing systems. This draft report will follow the reporting recommendations of MASH and will be submitted to the technical representative of the Roadside Safety Pooled Fund for review and approval.

The TTI research team will also prepare application documentation for FHWA Eligibility Letters for the systems who meet FHWA Eligibility Letter requirements. For the other systems, the research team will prepare engineering justification explaining that the critical tests were performed.

TTI Research Supervisor:
James C. Kovar, E.I.T.
Associate Transportation Researcher
Texas A&M Transportation Institute
TAMU 3135
College Station, Texas 77843-3135
(979) 458-3874
[email protected]
Pooled Fund Technical Representative:
Joe Hall, P.E., P.S.
Technical Policy QA/QC Engineer
Value Engineering Coordinator
West Virgina Division of Highways
1334 Smith Street
Charleston, WV 25305-0430
(304) 414-6442
[email protected]

2018-05-08
2020-04-27