Recent crash testing of small and medium sign supports and work-zone devices has been problematic for both of the test vehicles required in the 2009 AASHTO Manual for Assessing Safety Hardware (MASH). Many of these designs have previously been successfully full-scale crash tested under NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. Only the small car (1800-lb, Geo Metro or similar) test was performed under NCHRP Report 350. MASH requires testing with both a small car (2420-lb, Kia Rio or similar) and a pickup truck (5000-lb, ½-ton Dodge Quad Cab or similar) into these types of devices. Occupant Impact Velocities (OIVs) and Occupant Ride-Down Accelerations (ORAs) have not been a problem because of the increased weight of the test vehicles, even with the commensurate reduction in impact speed in MASH Test 3-60. However, the change in frontal geometry (i.e., bumper heights, increased frontal area, and wrap around distances) and increased ground clearance has changed the interaction between the vehicle and object struck. In general, small and medium sign supports used to pass over the top of the impacting vehicle with limited or no vehicle contact. With the newer MASH test vehicles, sign supports are now striking the windshield and roof of the test vehicles and failing the occupant compartment intrusion and/or penetration requirements of MASH. Similarly, vehicle collisions with portable work-zone devices are causing unacceptable windshield and roof penetrations and/or deformations as well as floor pan penetrations. No testing has been conducted to date on luminaires (light poles) under MASH, but this recent testing on other breakaway and portable work-zone devices raises questions as to the expected performance of breakaway luminaire poles under the MASH impact safety criteria. The addition of objective vehicle intrusion and deformation criteria has also brought into question the future usefulness of pendulum/bogie testing of breakaway and crashworthy designs.
The objective of this research is to identify and evaluate the crash performance of breakaway sign and luminaire supports and crashworthy work-zone traffic control devices that are non-proprietary and commonly used. The evaluation should address their in-service safety performance, potential failure modes (and, if possible, design modifications that might address those failure modes), and their likelihood to comply with the current MASH crash test criteria.
Accomplishment of the project objective will require at least the following tasks.
(1). Identify non-proprietary designs for breakaway sign and luminaire supports and crashworthy work-zone traffic control devices that are commonly used in the United States. By use of a survey or other means, estimate the prevalence of each of these designs. (2). Compile and review available crash test results (MASH and NCHRP 350) and FHWA Acceptance or Eligibility Letters for the designs identified in Task 1. Summarize the results for each design. (3). Collect information on the frequency of these designs not performing as intended in a crash and the impact of the adverse performance on the severity of the crash. For work-zone devices, consideration should be given to how the device is presented (e.g., position, orientation) when it is not in use but still in the clear zone. (4). Recommend designs for further evaluation in Tasks 6 and 7, based on, at a minimum, the prevalence of the design, the in-service safety performance, and the likelihood of meeting MASH test criteria.(5). Prepare a Phase I technical interim report to document the findings of the previous tasks, a draft outline for the final report, and an updated work plan for Phase II.
(6). For the designs specified in the Phase II work plan authorized by NCHRP, perform finite element modeling simulations to identify potential problems in meeting MASH test criteria.(7). For some of the designs studied in Task 6, conduct full-scale crash tests to corroborate the simulation results. (8). If possible, identify potential changes to the designs studied in Tasks 6 and 7 and similar designs to improve their likelihood of meeting MASH test criteria. (9). Based on the results of Tasks 6 and 7 and the research team’s experience, make an assessment of whether and how surrogate vehicle testing and/or finite element simulation could be used to reduce the costs of crash testing under MASH test criteria. (10). Prepare a final report documenting the entire research effort including an executive summary and the research team’s recommendation of research needs and priorities. Recommendations for updates to the MASH test criteria should be included as an appendix. A PowerPoint presentation should be included in the final deliverables describing the project background, objective, research method, findings, and conclusions that summarize the project for an executive or management-level audience.