Guardrail System Research Articles

Standard Midwest Guardrail System Placed at 1V:2H Slope Break Point or with Omitted Post

State departments of transportation (DOTs) throughout the United States commonly use W-beam guardrail systems to keep errant vehicles from leaving high-speed roadways and encountering safety hazards adjacent to the roadway edge, such as steep roadside slopes. Additionally, although W-beam guardrail is used to protect errant vehicles from safety hazards along the roadways, obstructions at post locations within a run of guardrail are a common occurrence. State DOTs wanted to evaluate the standard Midwest Guardrail System (MGS) for use in these instances. First, the standard MGS with 6-ft (1,829-mm) W6 × 8.5 (W152 × 12.6) steel posts spaced at 75 in. (1,905 mm) placed at the slope break point of a 1V:2H slope was successfully crash tested and evaluated according to the Test Level 3 (TL-3) safety performance criteria presented in the Manual for Assessing Safety Hardware (MASH). Subsequently, the standard MGS with one omitted post, which created an unsupported span of 12.5 ft (3.8 m), was full-scale crash tested, and it satisfied the MASH TL-3 safety performance criteria. Because multiple variations of the MGS system have been developed for special applications, recommendations for the omission of a post or installation on a steep slope will vary depending on the nature and behavior of the application. The safety performance of various MGS configurations and special applications was compared. Implementation guidance was then given about the use of the MGS placed at the slope break point and omitting a post in the MGS with MGS special applications. These special applications included terminals and anchorages, MGS stiffness transition to thrie beam approach guardrail transitions, MGS long-span system, MGS adjacent to 1V:2H fill slopes, MGS on 1V:8H approach slopes, MGS in combination with curbs, wood post MGS, and MGS without blockouts.

Crashworthiness of G4(2W) guardrail system: a finite element parametric study

ABSTRACTIn recent years, vehicle demographics have changed to include a relatively large proportion of light trucks, such as pickups, vans and sport-utility vehicles. It is found that several types of guardrail systems, including the G4(2W) guardrail system, are unable to redirect the pickup trucks to roadway safely. Therefore, in this study, several options are considered; they include improving the splice connections and adjusting the guardrail height and the post spacing to improve the performance of this system. The G4(2W) guardrail system is modelled in LS-DYNA and validated with a previous full-scale crash test conducted by the Texas A&M Transportation Institute. A parametric study based on the results of the LS-DYNA crash simulation according to Length of Need test 3-11 and 3-10 is conducted to investigate key factors of guardrail systems, including the splice configuration, the post spacing and the guardrail height. The purpose of this study is to find a model that satisfies the requirements of Test Level 3 outlined in Manual for Assessing Safety Hardware (MASH)'s criteria.

Optimal guardrail runout lengths for freeways

ABSTRACTGuardrails have commonly been installed to prevent errant vehicles from impacting roadside hazards. However, guardrail impacts have contributed to numerous serious injuries and fatalities. Plus, guardrails are generally impacted more often because they are installed closer to the edge of travel way and are much longer than the shielded hazard itself. Thus, to reduce the frequency of guardrail crashes, an optimized length should be determined. The American Association of State Highway and Transportation Officials (AASHTO) Roadside Design Guide (RDG) has suggested guardrail runout lengths which are dependent on posted speed limit and traffic volumes. Crash data analyses and simulation using the recently-updated Roadside Safety Analysis Program (RSAPv3) was conducted to evaluate the guardrail length-of-need (LON) associated with the lowest crash cost (i.e., cost associated with injuries and property damage) and maximum cost-effectiveness for freeways. Crash data involving Kansas guardrail systems, which were compliant with recommendations provided in the 2006 AASHTO RDG and occurring on freeways with divided medians, were collected and analyzed. The frequency, rate, and risk of shielded hazard crashes were extremely low. RSAPv3 analyses indicated that there was an economic and safety benefit to reducing the installed LON as well as utilizing different runout lengths for left- and right-side departures for divided roadways.

Effect of crushable blockouts on a full-scale guardrail system

ABSTRACTSince the performance of the guardrail system depends in part on the compatibility of vehicle-to-roadside hardware, it is important to improve the interaction of the vehicle with the guardrail system by adding more compliance to the guardrail system. In this paper, a finite-element baseline model of a guardrail system consisting of a light truck (2000 kg) travelling at 100 km/h and striking a guardrail was developed in accordance with the NCHRP Report 350 guidelines for Test Level 3 safety performance. The model was validated through comparison to a full-scale test conducted by the Texas Transportation Institute. In order for the guardrail system to absorb more energy and offer better stability to the vehicle, a rigid wooden blockout was replaced by a new crushable blockout design that was evaluated at the component level. The new blockout was formed by three crash cans and triggered at the corner, then was implemented in the full-scale model. The results of the analysis indicate that the both models satisfy the requirements of NCHRP Report 350 for the Test 3-11 conditions and show that the crushable blockout offers better vehicle stability in terms of roll angle and vehicle deceleration.

Classifying construction site photos for roof detection

Purpose Roofing is one of the most dangerous jobs in the construction industry. Due to factors such as lack of planning, training and use of precaution, roofing contractors and workers continuously violate the fall protection standards enforced by the US Occupational Safety and Health Administration. A preferable way to alleviate this situation is automating the process of non-compliance checking of safety standards through measurements conducted in site daily accumulated videos and photos. As a key component, the purpose of this paper is to devise a method to detect roofs in site images that is indispensable for such automation process. Design/methodology/approach This method represents roof objects through image segmentation and visual feature extraction. The visual features include colour, texture, compactness, contrast and the presence of roof corner. A classification algorithm is selected to use the derived representation for statistical learning and detection. Findings The experiments led to detection accuracy of 97.50 per cent, with over 15 per cent improvement in comparison to conventional classifiers, signifying the effectiveness of the proposed method. Research limitations/implications This study did not test on images of roofs in the following conditions: roofs initially built without apparent appearance (e.g. structural roof framing completed and undergoing the sheathing process) and flat, barrel and dome roofs. From a standpoint of construction safety, while the present work is vital, coupling with semantic representation and analysis is still needed to allow for risk analysis of fall violations on roof sites. Originality/value This study is the first to address roof detection in site images. Its findings provide a basis to enable semantic representation of roof site objects of interests (e.g. co-existence and correlation among roof site, roofer, guardrail and personal fall arrest system) that is needed to automate the non-compliance checking of safety standards on roof sites.

Performance of metallic defences submitted to vehicle impact

The main function of a road guardrail is to redirect an out of control vehicle avoiding a frontal collision or a dangerous veering off the road trajectory. Second, the energy absorption imposed by barrier deformation or any other energy dissipation method is beneficial to the car occupant safety. This study evaluates the performance of a W-Beam guardrail system, in accordance to Brazilian Standards, in respect to the kinetic energy absorption and to the vehicle return angle to the road. This evaluation of the guardrails is performed in a virtual environment using the finite element method. For the correct representation of the model, the material was characterised through experimental tests. Simplifications in the model are taken from the literature and a validated model of a vehicle is provided by the US National Crash Analysis Center.

Minimising lateral impact derailment potential at level crossings through guard rails

Derailments due to lateral collisions between heavy road vehicles and passenger trains at level crossings (LCs) are serious safety issues. A variety of countermeasures in terms of traffic laws, communication technology and warning devices are used for minimising LC accidents; however, innovative civil infrastructure solution is rare. This paper presents a study of the efficacy of guard rail system (GRS) to minimise the derailment potential of trains laterally collided by heavy road vehicles at LCs. For this purpose, a three-dimensional dynamic model of a passenger train running on a ballasted track fitted with guard rail subject to lateral impact caused by a road truck is formulated. This model is capable of predicting the lateral collision-induced derailments with and without GRS. Based on dynamic simulations, derailment prevention mechanism of the GRS is illustrated. Sensitivities of key parameters of the GRS, such as the flange way width, the installation height and contact friction, to the efficacy of GRS are reported. It is shown that guard rails can enhance derailment safety against lateral impacts at LCs.

Crashworthiness of guardrail posts embedded in cohesionless soils: a parametric study

ABSTRACTGuardrail systems are designed to provide a safe environment for vehicles and to reduce the severity of occupants’ injuries. The performance of this safety system is deemed to be vital to highway users. Guardrail post is probably the most important component of any guardrail system design. The evaluation of guardrail post's performance usually involves crash tests, which consist of colliding the post with a bogie. Crashworthiness tests try to cover a range of design parameters such as the soil resistance, impact velocity and blockout crushability. When reviewing the available various dynamic tests conducted to date, it is apparent that the range of the considered design parameters varies widely. Because of the lack of consistency of the diverse test conditions, the statistical analysis of the test results is not an easy task. In the present paper, the finite element method has been employed as a tool to conduct a parametric study and generate statistical data. The generated data are used to establish correlations between the post parameters and the system performance indicators.

Evaluation of the Midwest Guardrail System stiffness transition with curb

ABSTRACTA W-beam to thrie beam stiffness transition with a 102-mm (4-in.) tall concrete curb was developed to connect 787-mm (31-in.) tall W-beam guardrail, commonly known as the Midwest Guardrail System (MGS), to a previously developed thrie beam approach guardrail transition system. This upstream stiffness transition was configured with standard steel posts that are commonly used by several state departments of transportation. The toe of a 102-mm (4-in.) tall sloped concrete curb was placed flush with the backside face of the guardrail and extended the length of the transition region. Three full-scale crash tests were conducted according to the Test Level 3 (TL-3) safety standards provided in AASHTO's Manual for Assessing Safety Hardware (MASH). The first test, MASH Test No. 3-20, was deemed a failure due to guardrail rupture. The stiffness transition was modified to include an additional nested W-beam rail segment upstream from the W-beam to thrie beam transition element. MASH Test No. 3-20 was repeated on the modified system, and the 1100C small car was successfully contained and redirected. During MASH Test No. 3-21, a 2270P pickup truck was successfully contained and redirected. Following the crash testing program, the system was deemed acceptable according to the TL-3 safety performance criteria specified in MASH.

Structural behaviour of pultruded fibre composites guardrail system under horizontal loading

Fibre composite guardrails are increasingly being used to ensure safety of workers from fall-from-height incidents due to its high strength, high corrosion resistance and low maintenance. In this study, the structural behaviour of pultruded glass fibre-reinforced polymer (GFRP) guardrail was evaluated following AS1657-1992. GFRP guardrail systems mounted on top and side of a steel beam with different joint connectors are loaded horizontally to top of the guardrail post and to the middle of the guardrail member. The results showed that the guardrail system with joints connected with either polypin or rivets combined with epoxy exhibited 20% higher failure load and almost double the stiffness than those connected using polypin or rivets alone. The side-mounted guardrail failed due to failure of the base connector while the guardrail mounted on top of the beam failed at the joints indicating that the structural behaviour of GFRP guardrail system is affected mainly by the type of joints.

Injury Outcome in Crashes with Guardrail End Terminals

Objective: The goal of this study is to evaluate the crash performance of guardrail end terminals in real-world crashes. Guardrail end terminals are installed at the ends of guardrail systems to prevent the rail from spearing through the car in an end-on collision. Recently, there has been a great deal of controversy as to the safety of certain widely used end terminal designs, partly because there is surprisingly little real-world crash data for end terminals. Most existing studies of end terminal crashes used data from prior to the mid-1990s. Since then, there have been large improvements to vehicle crashworthiness and seat belt usage rates, as well as new roadside safety hardware compliant with National Cooperative Highway Research Program (NCHRP) Report 350, “Recommended Procedures for the Safety Performance Evaluation of Highway Features.” Additionally, most existing studies of injury in end terminal crashes do not account for factors such as the occurrence of rollover. This analysis uses more recent crash data that represent post-1990s vehicle fleet changes and account for a number of factors that may affect driver injury outcome and rollover occurrence.Methods: Passenger vehicle crashes coded as involving guardrail end terminals were identified in the set of police-reported crashes in Michigan in 2011 and 2012. End terminal performance was expected to be a function of end terminal system design. State crash databases generally do not identify specific end terminal systems. In this study, the coded crash location was used to obtain photographs of the crash site prior to the crash from Google Street View. These site photographs were manually inspected to identify the particular end terminal system involved in the crash. Multiple logistic regression was used to test for significant differences in the odds of driver injury and rollover between different terminal types while accounting for other factors.Results: A total of 1,001 end terminal crashes from the 2011–2012 Michigan State crash data were manually inspected to identify the terminal that had been struck. Four hundred fifty-one crashes were found to be suitable for analysis. Serious to fatal driver injury occurred in 3.8% of end terminal crashes, moderate to fatal driver injury occurred in 11.8%, and 72.3% involved property damage only. No significant difference in moderate to fatal driver injury odds was observed between NCHRP 350 compliant end terminals and noncompliant terminals. Car drivers showed odds of moderate to fatal injury 3.6 times greater than LTV drivers in end terminal crashes. Rollover occurrence was not significantly associated with end terminal type.Conclusions: Car drivers have greater potential for injury in end terminal crashes than light truck/van/sport utility vehicle drivers. End terminal designs compliant with NCHRP 350 did not appear to carry different odds of moderate driver injury than noncompliant end terminals. The findings account for driver seat belt use, rollover occurrence, terminal orientation (leading/trailing), control loss, and the number of impact events. Rollover and nonuse of seat belts carried much larger increases in injury potential than end terminal type. Rollover did not appear to be associated with NCHRP 350 compliance.

지주 형상에 따른 3차원 지반재료 모델의 경기장 보행자용 가드레일 동적성능 평가

This study investigated the embedded depth of guardrail posts through 3-D soil material model and carried out evaluation of the dynamic performance of guard rail. In order to calculate for embedded depth of sloping ground, displacement of guardrail posts is analyzed according to the embedded depth of experiment variables. Through the static test of guardrail posts, the maximum deflection was found to decrease the interval. By performing the dynamic test using the Bogie Car, that is confirmed the elastic modulus of the soil occuring the maximum deflection. Guardrail posts is considered to need for further reinforcement in the larger slope than the plains. This study researched about maximum displacement and deviation velocity through dynamic performance of guardrail system and conducted analysis about protection performance evaluation of passenger.

Dynamic strength of a modified W-beam BCT trailing-end termination system

W-beam systems utilise end-terminal anchorages to develop tension upstream and downstream of an impact event. However, the capacities of the anchorage components under impact loading are not well known. One such W-beam end-anchorage system, the Midwest guardrail system (MGS) trailing-end anchorage, was evaluated using three dynamic component tests – a soil foundation tube pull test, a breakaway cable terminal (BCT) post splitting test, and an MGS end-anchorage system pull test. The peak load recorded during a soil foundation tube test was 193 kN at 56 mm deflection, as measured at the ground line. BCT posts split at loads of 17.8 and 32.9 kN. The end-anchorage tensile capacity was 156 kN, dissipating 64.7 kJ. Results from the component tests were also used to create and validate nonlinear finite element models of the components in order to be used for future design and analysis of end anchorages.

Occupant Risk Analysis for Guardrail Roadside Safety Barrier Systems: Analysis and Evaluation of Full Scale Crash Tests

Collision with roadside objects such as trees, utilities and guardrail are a major road-safety problem and reported the highest rate of side-impact accidents on roadways in which about 225,000 people have been involved. In this study the common methods to evaluate occupant risk factors involving in crash to roadside barrier systems are reviewed. The collected previous real crash test on guardrail system with regards to occupant impact risk factors are prepared based on different system performance. Higher average for longitudinal impact velocity for Thrie-beam system is found. On the other hand, Weak-post system is provided less severe system in terms of longitudinal impact velocity.

Minimum Effective Length for the Midwest Guardrail System

The recommended minimum length for the standard Midwest Guardrail System (MGS) is 175 ft (55.3 m) based on crash testing according to NCHRP Report 350 and AASHTO's Manual for Assessing Safety Hardware (MASH) specifications. However, varying roadside hazards and roadway geometries may require a W-beam guardrail system to be shorter than the currently tested minimum length. The effects of reducing system length for the MGS were therefore investigated. The research study included one full-scale crash test with a Dodge Ram pickup truck striking a 75-ft (22.9-m) long MGS system. The barrier system satisfied all MASH Test Level 3 (TL-3) evaluation criteria for Test Designation Number 3-11. Test results confirmed that the reduced system length did not adversely affect overall system performance or deflections. Simulations that used BARRIER VII and LS-DYNA were also conducted to analyze system performance with reduced lengths of 50 ft (15.2 m) and 62 ft 6 in. (19.1 m). Both system lengths exhibited the potential for successfully redirecting an errant vehicle at MASH TL-3 test conditions. However, these reduced-length systems would have a narrow window for redirecting vehicles and would be able to shield hazards of only a limited size. Owing to limitations associated with the computer simulations, full-scale crash testing is recommended before these shorter systems are installed.

Cost-Effective Safety Treatment of Trees on Low-Volume Rural Roads

Generally, trees are naturally occurring fixed objects that are found along many roadways and that potentially pose safety risks to errant motorists. Unfortunately, trees have been responsible for numerous fatal and serious injury crashes during run-off-road events. This study included an incremental benefit-to-cost (B-C) analysis that used the Roadside Safety Analysis Program to investigate the efficacy of safety treatment alternatives for trees on roadways with volumes of less than 500 vehicles per day (vpd) and speed limits of 55 mph (88.5 km/h) or greater. The study was based on a parametric analysis of site characteristics from a field survey in Kansas. It used four tree groupings, three tree diameters, and four lateral offsets from the roadway to configure 120 scenarios. Three safety treatment methods were considered: (a) a do-nothing option representing the baseline condition; (b) tree removal, with cost estimates coming from reliable sources; and (c) a crashworthy guardrail system. For various reasons, the guardrail system was no more cost-effective than the do-nothing or tree removal options. B-C ratios were used to recommend tree removal on the basis of several pertinent variables. In all cases, B-C ratios for tree removal were never less than 1.0, which indicated limited justification for keeping the trees. Tree removal was considered the safest and primary alternative when trees were far from other fixed obstacles. Because these guidelines are based solely on B-C analyses, the road designer or engineer is encouraged to use them as a foundation for making safety improvements but also to consider site-specific investigation and analysis.

Development and Effective Use of a Wire Rope Guardrail System for Two-lane Roads in Japan

Fatal high-speed head-on collisions often occur in the limited spaces of two-lane roads without median strips. Wire rope guardrail systems can be seen as an alternative to median strips. Such systems use thin posts, have a buffering function and require minimal width. The purpose of this study was to develop a wire rope guardrail system with a buffering function as a separator for two-lane roads. CG simulation and collision experiments using real vehicles were conducted to determine the necessary characteristics of the fence, and performance tests were conducted in accordance with guard fence installation criteria. As a result, a wire rope guardrail system that satisfies Japan's Am Performance Standard Criteria for expressway median strips was developed. A driving test was conducted to study the feasibility of introduction to two-lane expressways.

Design and Full-Scale Testing of Low-Cost Texas Department of Transportation Type T631 Bridge Rail for MASH Test Level 2 and 3 Applications

The purpose of this project was to design and test a low-cost bridge rail system that would be compatible with the Midwest Guardrail System (31 in. height) and minimized or eliminated deck damage when impacted by errant vehicles. The Texas Type T631 bridge rail developed for this project is a flexible, low-cost bridge rail system for Test Level 2 (TL-2) applications. The Texas Department of Transportation Type T631 bridge rail designed and developed for this project was evaluated under Manual for Assessing Safety Hardware (MASH) TL-2 in 2013. The bridge rail incorporated S3X5.7 steel sections designed to yield at the post baseplate. The post baseplate was designed to distribute the baseplate bearing and shear forces without causing damage to the 8-in.-thick reinforced concrete deck. The welds on the posts were designed such that the post yielded without tearing away from the top of the baseplate. The rail element consisted of a 12-gauge W-beam rail element. The rail element was attached to the post with a bolt of diameter 5/16 in. This bolt was designed to break away without adversely affecting vehicle performance. The posts were spaced 6 ft 3 in. on centers for TL-2. The post spacing was reduced to 3 ft 1½ in. on centers and evaluated for MASH Test Level 3 (TL-3) specifications in 2014. At the smaller post spacing, the T631 met all the performance requirements of MASH TL-3. Details of the design and testing of the T631 for MASH TL-2 and MASH TL-3 specifications are provided in this paper.

Worst-Case Connection Strength Considerations in Designing Certification Crash Test Experiments for W-Beam Guardrail

Certification crash test experiments conducted in controlled laboratory environments play a crucial role in the product development cycle of roadside safety hardware by linking analysis, design, and real-world in-service performance along low-volume roads (LVRs). The AASHTO Manual for Assessing Safety Hardware worst-case testing philosophy prescribes a commonsense approach to ensuring reliable real-world performance in designing certification crash test experiments for W-beam guardrails. Literature of the past two decades establishes extreme rail-to-post connection strength variability as a component-level trigger mechanism of guardrail system-level failure modes that degrade the reliability of guardrail safety performance. A range of primary and secondary release mechanisms with their associated variability sources is examined from the perspective of characterizing the worst case for each release mechanism. A case is made to support a recommendation that worst-case connection strength be systematically represented in designing certification crash test experiment matrices that are intended to ensure adequate performance of guardrails along LVRs. A systematic general methodology is introduced for defining compounded worst-case connection strength. The standard button head mounting bolt of the modified G4(1S) and Midwest Guardrail System family is considered as an example. Detailed evaluation of variability extremes in button head bolt connection strength indicates that optimizing the existing button head bolt release mechanism is not possible, even with the use of mid-span splices. Thus, it is recommended that an optimized release mechanism solution—such as the Gregory Mini Spacer guardrail fastener—be considered, consistent with the award-winning science of release for guardrail optimization to improve roadside safety along LVRs and other roadways in the United States, Europe, and developing countries.

3차원 지반재료 모델기반의 다양한 지주형상을 갖는 노측용 가드레일의 동적성능 평가

3차원 지반재료 모델기반의 다양한 지주형상을 갖는 노측용 가드레일의 동적성능 평가