NCHRP Project 22-43: Implementation of MASH for Sign Supports, Breakaway Poles, and Work Zone Traffic Control Devices (Completed)

BACKGROUND 
To encourage state departments of transportation (DOTs) and hardware developers to advance hardware designs, the Federal Highway Administration (FHWA) and the American Association of State Highway and Transportation Officials (AASHTO) collaborated on the development of the AASHTO Manual for Assessing Safety Hardware (MASH) implementation policy that includes sunset dates for various roadside hardware categories. The joint FHWA/AASHTO implementation plan for MASH devices requires highway agencies to evaluate many different designs of permanent sign supports, breakaway poles, and work zone traffic control devices (herein called “Systems”). The FHWA and AASHTO implementation plan requires Systems installed on national highway systems after December 31, 2019 to comply with MASH 2016.

A significant number of Systems still need to be evaluated to comply with MASH. For each System, up to three full-scale crash tests need to be conducted on each variation and these crash tests can be expensive. There are thousands of variations of Systems that state DOTs utilize. The costs of these tests will fall directly on transportation agencies and the public. Since it is not feasible to test all possible combinations in MASH, there is a need to provide guidelines to aid state DOTs in selecting appropriate testing protocols to evaluate the crashworthiness of Systems.

OBJECTIVE
The objective of this research is to develop guidelines for implementation of, and propose modification to, AASHTO MASH for sign supports, breakaway poles, and work zone traffic control devices, including examples to demonstrate the application of the proposed guidelines.

The research includes developing testing protocols that are validated by crash simulations and testing for families of related devices within the following three groups: (1) sign supports, (2) breakaway poles, and (3) work zone traffic control devices. For the purposes of this research, a family of related devices is a set of similar devices within one of the three groups that share the same critical characteristics controlling crashworthiness.

STATUS: Completed. The final report has been received and will be published as NCHRP Report 1123: Guidelines for Evaluating Crashworthiness of Sign Supports and Breakaway Luminaire Poles. The appendices will be published as NCHRP Web-Only Document 405: Evaluating Crashworthiness of Sign Supports and Breakaway Luminaire Poles: Appendices.

BACKGROUND

Assessing the crashworthiness of luminaire poles presents a unique set of challenges.

• Separate companies typically manufacture breakaway bases, poles, and connection hardware. Due to the various configurations of products, it is difficult to determine if a particular breakaway base or hardware is MASH compliant with other pole styles and determine the party responsible for testing each combination.
• The vehicle fleet has changed significantly since the 1980s and 1990s when most research was conducted on breakaway poles.
• Previous testing criteria for poles concentrated on acceptable change in velocity and maximum stub height; however, current MASH testing criteria also include a maximum of 4 inches of roof crush. Unfortunately, little or no data collected from NCHRP Project 350 crash testing provides the extent of roof crush or performance of existing pole configurations with current MASH testing criteria. 

Research conducted by FHWA set the maximum weight and height of poles and associated hardware. These values need to be reevaluated with current MASH criteria, including roof crush. Current computer models appear to overestimate roof crush for signs and the lack of accuracy in computer modeling makes it difficult to use computer modeling to predict likely success in crash testing for poles.

OBJECTIVES

There are two objectives: (1) determine the maximum height and weight of breakaway poles and hardware that will meet MASH requirements and (2) investigate if the criterion of a 4-inch-tall object on a 5-foot chord is appropriate for the current vehicle fleet. Research efforts for Objective 1 will include:

• Physical tests to correlate roof crush with pole and hardware height and weight and aid in determining critical pole configurations, and
• Dropping poles with associated hardware of varying heights and weights onto vehicles as a precursor to full-scale crash testing. 

The findings will be used to identify improvements to vehicle computer models to better simulate crash testing roof crush. Research efforts for Objective 2 will: 

• Review procedures used to develop the 4-inch-tall object on a 5-foot chord criteria,
• Determine if the procedure can be improved, and
• Analyze procedures with a current vehicle fleet.

Results from this research may help guide future improvements to MASH, the Roadside Design Guide, and other AASHTO documents.