| TTI Research Supervisor: Sofokli Cakalli Assistant Research Scientist Texas A&M Transportation Institute Texas A&M University System TAMU 3135 College Station, Texas 77843-3135 (512) 998-6039 [email protected] | Pooled Fund Technical Representative: Derwood C. Sheppard, Jr., P.E., M.Eng. Standard Plans Publication Engineer FDOT Roadway Design Office Florida Department of Transportation 605 Suwannee Street Tallahassee, FL 32399-0450 (850) 414-4334 [email protected] |
In 2016, the American Association of State Highway and Transportation Officials (AASHTO)
published an updated edition of the Manual for Assessing Safety Hardware (MASH) document
(1). Along with this, the Federal Highway Administration (FHWA) and AASHTO developed a
revised joint implementation agreement that establishes dates for discontinuing the use of safety
hardware that has met earlier crash testing criteria for new installations and full replacements on
the National Highway System (NHS). Although some support structures testing was performed
during the development of the updated criteria, many breakaway systems and other roadside
safety features have yet to be evaluated under the proposed guidelines. As we continue the MASH
implementation agreement for National Cooperative Highway Research Program (NCHRP) 350
devices, evaluation of the remaining widely used roadside safety features using the safetyperformance evaluation guidelines included in MASH 2016 is an imminent need.
Pedestrian and small traffic signals are needed at many intersections and pedestrian crossings
where there is no other post or poles for which to attach to. Also, the Americans with Disabilities
Act (ADA) current guidance recommends separated pedestrian detector and actuators, which
require separate posts to be installed. There is a need to evaluate and crash test these structures
under MASH criteria.
The purpose of this research is to evaluate the MASH crashworthiness of common assembly
configurations using an engineering analytical approach and full-scale crash tests.
A survey will be conducted to identify the common pedestrian and small traffic assemblies used
by the member states. An analytical engineering analysis will follow to evaluate the assemblies
and select the most critical and representing configurations for full scale crash testing. A summary
of the performed work and crash test results will be presented in a report indicating MASH
compliance of the crash tested assemblies.
The 2016 MASH edition is the latest in a series of documents that provided guidance on testing
and evaluation of roadside safety features. The original MASH document was published in 2009
and represents a comprehensive update to crash test and evaluation procedures to reflect changes
in the vehicle fleet, operating conditions, and roadside safety knowledge and technology (2). The
MASH documents supersede the NCHRP Report 350, ‟Recommended Procedures for the Safety
Performance Evaluation of Highway Features” standards (3).
The FHWA issued a January 7, 2016, memo mandating the AASHTO/FHWA Joint
Implementation Agreement for MASH with compliance dates for installing MASH hardware that
differ by hardware category. After December 31st, 2019, all roadside safety devices must have
been successfully tested and evaluated according to the 2016 MASH standard edition. FHWA
will no longer issue eligibility letters for highway safety hardware that has not been successfully
crash tested according to the 2016 MASH edition evaluation criteria.
Signs, luminaire poles, and other breakaway devices consist of vertical structural supports that can
be an obstacle for errant vehicles. Breakaway devices, mainly used with sign and luminaire
supports and utility poles, involve mechanical fuses that require a certain amount of kinetic energy
to be activated. The guidelines for testing such systems include a low-speed test to evaluate the
assembly’s activation energy. Furthermore, there is some concern about excessive deceleration,
vehicle instability and occupant compartment intrusion during high-speed impact with these types
of structures. Due to the capability for a higher level of safety than longitudinal barriers and other
roadside safety hardware, the occupant risk criteria for breakaway structures are more stringent
than those used for crash cushions and longitudinal barriers.
The subject hardware of this project, pedestrian signals and small traffic signs, are part of the
breakaway devices category. The two most common support designs used by the member states
for these features are the 4-bolt slip base and the pedestal base. Both designs will be evaluated in
this project.
The research objective is to evaluate pedestrian and small traffic signs for MASH compliance.
Specifically, the researchers will use an analytical engineering methodology to assess the most
common assemblies provided by the member states. Then, the two most critical and representing
configurations will be crash tested under MASH test level 3 (TL-3) conditions.
Pedestrian signals and small traffic signs are needed at many intersections and pedestrian
crossings where there is no other post or poles for which to attach to. Also, current ADA guidance
recommends separated pedestrian detector and actuators, which require separate posts. These
breakaway assemblies need to be evaluated under MASH conditions.
This research will provide a report indicating MASH compliance of the crash tested assemblies
and make recommendations based on results.
This project will provide a report indicating MASH compliance of pedestrian signal assemblies
and small traffic signal supports.
The proposed work plan consists of four tasks as described below.
Task 1: Literature Review & Survey
The TTI research team will perform a literature review for past and current research on
pedestrian and small traffic signal evaluations. In addition, the research team will conduct a
survey among Roadside Safety Pooled Fund members to gather current state standards or
drawings and identify the most common designs.
Task 2: Engineering Analysis on Selected Configurations
From the results gathered in Task 1, the TTI research team will conduct an engineering analysis
using an analytical approach on the most common and critical configurations among the states.
Given the nature of this analytical approach, the research team anticipates analyzing a large
number of configurations in Task 2.
Based on the engineering analysis, the TTI research team will recommend the two most
representing and most likely to comply with MASH assemblies for full scale crash testing.
Task 3: System Construction & Full-Scale Crash Testing
In Task 3, the TTI research team will perform two full-scale crash tests on both configurations
recommended in Task 2. Specifically, MASH test 3-61 and test 3-62 will be conducted on each
assembly.
Given the shape and size of attachments on the pedestrian and small traffic signals, the research
team considers that crash testing these devices from only one direction will be sufficient.
Therefore, the two recommended assemblies will be crash tested only in one direction. That
critical impact angle will be identified during the engineering analysis in Task 2.
Task 4: Documentation and Reporting
The TTI research team will generate a final report of the research findings. The report will
indicate MASH compliance of crash tested assemblies and provide recommendations.
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