Development and Evaluation of Weak-Post W-Beam Guardrail in Mow Strips

The objective of this study was to adapt and evaluate a weak-post, W-beam guardrail system for use within mow strips and other pavements. The weak-post guardrail system was originally designed as the MGS bridge rail and has also been adapted for use on culverts. It was envisioned that the weak-post design would absorb the impact forces and prevent damage to the mow strips, thereby minimizing maintenance and repair costs. Evaluation of the weak posts in mow strips began with three rounds of dynamic bogie testing. Round 1 of bogie testing showed that 4-in. (102-mm) thick concrete would sustain only minor spalling from impacts to the posts. However, the posts would push through 4-in. and 6-in. (102-mm and 152-mm) thick asphalt mow strips. During Round 2, 24-in. (610-mm) long, 4-in. x 4-in. (102-mm x 102-mm) sockets with 10-in. x 9-in (254-mm x 229-mm) shear plates were utilized to better distribute the impact load to the asphalt pavement and prevent damage. However, Round 3 of bogie testing consisted of dual-post impacts, and the asphalt suffered from shear block fracture between the two 24-in. (610-mm) sockets and the back edge of the mow strip. A dual-post test within a 4-in. (102-mm) thick concrete pad showed only minor spalling. A full-scale MASH 3-11 test was conducted on the weak-post guardrail system installed within an asphalt mow strip. Due to the Round 3 testing results, the asphalt thickness was increased to 6 in. (152 mm), and the socket depth was increased to 30 in. (762 mm). The 2270P pickup was contained and safely redirected, and all MASH safety criteria were satisfied. Unfortunately, the asphalt fractured, and a 2ó-in. (64-mm) wide crack ran from socket to socket throughout the impact region of the system. Therefore, the weak-post guardrail system was crashworthy, but would require repairs in its current configuration. The system could also be installed in a concrete mow strip to prevent pavement damage

Analysis of Existing Work-Zone Sign Supports Using Manual for Assessing Safety Hardware Safety Performance Criteria

Over the years, numerous work-zone, portable sign support systems have been successfully crash tested according to the Test Level 3 safety performance guidelines provided in the National Cooperative Highway Research Program Report 350 and accepted for use along our nation’s highways. For this study, several crashworthy sign support systems were analyzed to predict their safety performance according to the new evaluation criteria provided in the Manual for Assessing Safety Hardware (MASH). More specifically, this analysis was conducted to determine which hardware parameters negatively affect a system’s safety performance. To verify the accuracy of the analysis, eight systems, four with the 2270P pickup truck and four with the 1100C small car, were evaluated according to the MASH criteria. Five out of the eight tested systems failed the MASH criteria, and the other three systems performed in an acceptable manner. As a result of the analysis and verification, several hardware parameters were deemed critical for contributing to system failure under MASH and included sign panel material, top mast height, presence of flags, sign-locking mechanism type, base layout, and system orientation. Flowcharts were developed to assist manufacturers with the design of new sign support systems

Development of MASH TL-3 Transition Between Guardrail and Portable Concrete Barriers

Often, road construction causes the need to create a work zone. In these scenarios, portable concrete barriers (PCBs) are typically installed to shield workers and equipment from errant vehicles as well as prevent motorists from striking other roadside hazards. For an existing W-beam guardrail system installed adjacent to the roadway and near the work zone, guardrail sections are removed in order to place the portable concrete barrier system. The focus of this research study was to develop a proper stiffness transition between W-beam guardrail and portable concrete barrier systems. This research effort was accomplished through development and refinement of design concepts using computer simulation with LS-DYNA. Several design concepts were simulated, and design metrics were used to evaluate and refine each concept. These concepts were then analyzed and ranked based on feasibility, likelihood of success, and ease of installation. The rankings were presented to the Technical Advisory Committee (TAC) for selection of a preferred design alternative. Next, a Critical Impact Point (CIP) study was conducted, while additional analyses were performed to determine the critical attachment location and a reduced installation length for the portable concrete barriers. Finally, an additional simulation effort was conducted in order to evaluate the safety performance of the transition system under reverse-direction impact scenarios as well as to select the CIP. Recommendations were also provided for conducting a Phase II study and evaluating the nested Midwest Guardrail System (MGS) configuration using three Test Level 3 (TL-3) full-scale crash tests according to the criteria provided in the Manual for Assessing Safety Hardware, as published by the American Association of Safety Highway and Transportation Officials (AASHTO)

Transition of Temporary Concrete Barrier

The objective of this research was to design a transition from temporary concrete barriers to a permanent concrete barrier for median applications. The researchers at Midwest Roadside Safety Facility utilized a combination of free-standing and tied-down Kansas temporary concrete barriers and a dual-nested thrie beam for the transition to the single-slope permanent barrier as well as a transition cap. Two full-scale vehicle crash tests were performed on the system. Evaluation of the approach transition required testing at two Critical Impact Point (CIP) locations. The first tests was performed using a half-ton pickup truck that impacted the temporary barriers 1,432 mm upstream from the permanent barrier, at a speed and angle of 100.7 km/h and 24.7 degrees, respectively. The second crash test was also performed using a half-ton truck that impacted the temporary barriers 16.6 m upstream from the permanent barrier, at a speed and angle of 100.1 km/h and 26.2 degrees, respectively. Both tests were conducted and reported in accordance with requirements specified in the Manual for Assessing Safety Hardware (MASH) and were determined to be acceptable according to the Test Level 3 (TL-3) evaluation criteria

Racetrack SAFER barrier on temporary concrete barriers

Previously, the Steel and Foam Energy Reduction (SAFER) barrier system was successfully developed and crash tested for use in high-speed racetrack applications for the purpose of reducing the severity of racecar crashes into permanent, rigid, concrete containment walls. The SAFER barrier has been implemented at all high-speed oval race tracks that host events from NASCAR’s top three race series and IRL’s top series. However, there are a number of racetrack facilities in the United States that use temporary concrete barriers as a portion of the track layout during races. These barriers are typically used on race tracks to shield openings or protect portions of the infield. Some of these temporary barrier installations are in areas where current safety guidance would recommend treatment with the SAFER barrier. Thus, a system was successfully designed, tested, and evaluated for a system targeted towards the most pressing need in the US motorsports industry, a system for spanning openings between rigid concrete parapets on the inner walls of various race tracks