W-beam Guardrail System Research Articles

Dynamic response of piles embedded in granular soil to lateral impacts

Soil-embedded vehicle barriers, such as W-beam guardrail systems, play a pivotal role in transportation safety, mitigating the risks associated with vehicular collisions with roadside hazards. The efficacy of these barriers greatly depends on the pile-soil system's kinetic energy dissipation capability during vehicular impacts. However, a comprehensive understanding of how soil strength, embedment depth, and impact velocity collectively govern the dynamic behavior of the pile-soil system remains a gap in current research. This study explores the dynamics of lateral impacts on piles embedded in various granular soils. The process of dynamic lateral impact and interaction between the pile and the soil was modeled using the Updated Lagrangian Finite Element Method (UL-FEM). A damage-based element erosion algorithm was incorporated into the model to accommodate severe mesh distortions and element entanglements of the soil material brought by the pile impact. Validation against well-documented large-scale physical impact tests ascertained the model's fidelity. Our findings elucidate the significant differences in resistive forces between piles in strong versus weak granular soils – notably, the former exhibited resistive forces roughly double their weaker counterparts under equivalent embedment depths and varied impact velocities. Intriguingly, a stiff pile in weak soil necessitates nearly double the embedment depth to match the energy dissipation of its strong-soil counterpart. Furthermore, the study discerned consistent depth of rotation point ranges for piles embedded in distinct soil strengths, regardless of embedment depth and impact velocity.

Development of a Bridge Railing Optimized for Rural, Low-Volume Roads

A new steel bridge rail was developed for use on rural, low-volume bridges. The railing consisted of 31-in. tall, 12-gauge W-beam guardrail mounted on S3x5.7 posts, which were supported by steel square-tube sockets. These side-mounted sockets were attached to the deck edge using a unique bolted design that connects directly to coupling nuts and threaded anchor rods embedded into the bridge deck. Thus, during a crash, the tensile impact loads are transferred directly to the anchor rods and the risk of damage to the deck edge is minimized. Full-scale crash testing was conducted according to test 2 to 11 of the AASHTO’s Manual for Assessing Safety Hardware (MASH). The test vehicle struck the bridge rail at 44.2 mph and an angle of 25.5° and was successfully contained and redirected. Damage to the bridge rail consisted of bent posts and deformed guardrail. No damage to the deck or sockets was observed. The tests passed all evaluation criteria of MASH test 2 to 11. The new railing was deemed crashworthy to MASH Test Level 2 (TL-2) with a post spacing of 75 in. Additionally, when the post spacing is reduced to 37.5 in., the railing was determined to be MASH Test Level 3 (TL-3) crashworthy through a comparison to similar, crash-tested, W-beam guardrail systems. BARRIER VII simulations showed that the new railing could be directly connected to the Midwest Guardrail System without a transition. Guidance was provided pertaining to the length of guardrail required adjacent to the bridge rail.

Multi-objective optimization design of post-soil system for enhanced W-beam guardrail containment performance

In the W-beam guardrail system, the post can provide sufficient lateral force through interaction with the subgrade and can create the necessary containment function by connecting with the W-beam rail panel. The purpose of this study is to evaluate the best embedment depth and section size of two different posts in the same subgrade from the perspectives of maximum lateral force and occupant ridedown acceleration for enhanced the containment performance of guardrail protection system in China. An accurate lateral force measurement method is used for the inertia effect in collision problems. And the exact finite element model of post-soil interaction is built by combining dynamic impact test with detailed finite element study. Then the Genetic algorithm (GA) was used to determine the optimum value of spread and then the GA-RBF was applied to construct the surrogate models of the analytical objective, which increased the accuracy of fitting. Finally, the embedment depth and structure size were obtained using multi-objective genetic algorithm. Full-scale crash test results show that the optimum design results meet the requirements. Through optimization design, W-beam guardrail has been greatly improved, which improves the crash safety of corrugated beam guardrail.

Evaluation of W-Beam Guardrail and Terminal Posts Installed in Metal Sleeves

Because of frozen soils in extreme winter weather, it is difficult to remove and replace soil-embedded posts of a W-beam guardrail system in the event of a vehicle crash. Additional resources and equipment are usually needed to repair the guardrail, which results in longer maintenance time or delays in carrying out the repair. This poses a safety hazard to the maintenance crew by increasing their exposure to the oncoming traffic, and to other motorists because of the presence of the maintenance crew or a non-functional guardrail. Some states install steel posts in metal sleeves for faster repairs under such conditions. However, the performance of the W-beam guardrail system and its terminals has not been evaluated with posts installed in sleeves under the Manual for Assessing Safety Hardware (MASH) criteria. Research presented in this paper evaluates the performance of the steel post W-beam guardrail and end terminals with posts installed in metal sleeves. A series of surrogate bogie vehicle impact tests and a full-scale crash test were performed to compare the performance of the posts installed in sleeves and the posts directly embedded in soil. Findings of this research show that steel posts may be installed in metal sleeves for the W-beam guardrail system and most end terminals.

Investigation and MASH Full-Scale Crash Testing of the Practice of Raising Blockouts on W-Beam Rail Systems

The Federal Highway Administration (FHWA) clarifies appropriate height measures for W-beam guardrails. Identification of existing locations where rail height is lower than recommended by FHWA is common. A research study was conducted to investigate the crashworthiness of raising blockouts on posts to restore barrier height and provide clarification on implementation of such methodology. The researchers evaluated the crashworthiness of raising blockouts by conducting a full-scale Manual for Assessing Safety Hardware (MASH) Crash Test 3-11 of a 28-in. W-beam guardrail system with composite blockouts raised 4 in. on posts. The 28-in. W-beam guardrail system with raised composite blockouts contained and redirected the 2270P vehicle, and it performed acceptably for MASH Test 3-11. The results of this study include guidance on the procedure for raising blockout mounting height on steel posts to achieve recommended rail height for a W-beam guardrail.

Development, Crash Testing, and Evaluation of Steel-Post Trailing-End Guardrail Anchorage System

Trailing-end guardrail anchorage systems are widely used by most state departments of transportation (DOTs) and generally consist of simple adaptations of crashworthy end terminals. The safety performance and structural capacity of these trailing-end anchorage systems, when reverse-direction impacts occur near the end, is imperative in crashworthiness of guardrail systems. In 2013, a non-proprietary trailing-end anchorage system with a modified breakaway cable terminal (BCT) was developed by the Midwest Roadside Safety Facility (MwRSF) for the Midwest Guardrail System (MGS). Although this trailing-end guardrail anchorage system adequately met the Manual for Assessing Safety Hardware (MASH) TL-3 safety requirements, the use of two breakaway wood posts was deemed by some users to have several drawbacks. Thus, there was a critical need to develop a non-wood option to anchor the downstream end of the W-beam guardrail system, which led to the need to develop a steel-post trailing-end guardrail anchorage system for use with the MGS. Following the design and component testing of such a system, two full-scale crash tests were performed according to the MASH 2016 test designation nos. 3-37a and 3-37b. In the first test, a 2270P pickup truck struck the guardrail system and was adequately contained and redirected. In the second test, an 1100C small car struck the barrier and safely gated through the barrier. Both tests were deemed acceptable according to TL-3 safety criteria in MASH 2016. Recommendations are provided for the installation of a steel-post trailing-end guardrail anchorage system when used in combination with MGS.

On analysis of double-impact test of 1500-kg vehicle into w-beam guardrail system

Every day on roads many scenarios of accidents may occur. One of the measures to minimize their consequences is road safety barriers. Finite Element analyses are being increasingly used to support the physical testing of these devices. The paper addresses the issue of a secondary impact into the previously damaged w-beam guardrail system. This situation belongs to one of the most dangerous which can happen on roads and may cause serious hazards, especially if the vehicle goes through the barrier. To evaluate the crashworthiness of the road barrier, the computational model of the crash test was developed and validated against the full-scale crash test. Then two simulations of TB32 crash tests were conducted on both damaged and undamaged road barriers to assess the influence of damage on the effectiveness of the safety system during vehicular impact. The study has revealed that the partially damaged system preserved some of its original functionality.

Development of a Test Level 3 Transition Between Guardrail and Portable Concrete Barriers

Road construction often requires that work zones be created and shielded by portable concrete barriers (PCBs) to protect workers and equipment from errant vehicles as well as to 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 so a PCB system can be placed. A study was done to develop a crashworthy transition between W-beam guardrail and PCB systems. Design concepts were developed and refined through computer simulation with LS-DYNA. Additionally, a study of critical impact points was conducted to determine impact locations for full-scale crash testing. The design effort resulted in a new system consisting of a Midwest Guardrail System that overlapped a series of F-shape PCB segments placed at a 15:1 flare. In the overlapped region of the barrier systems, uniquely designed blockout supports and a specialized W-beam end shoe mounting bracket were used to connect the systems. Three full-scale vehicle crash tests were successfully conducted according to the Manual for Assessing Safety Hardware Test Level 3 safety performance criteria. Because of the successful test results, a Test Level 3 crashworthy guardrail-to-PCB transition system is now available for protecting motorists, workers, and equipment in work zones.

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.

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.

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.

Weak-Post W-Beam Guardrail Attachment to Culvert Headwalls

A new W-beam guardrail system for use on low-fill culverts was developed and evaluated. The system was adapted from the Midwest Guardrail System (MGS) bridge railing for attachment to the outside face of culvert headwalls. Four attachment concepts were developed and evaluated through dynamic component testing. Both lateral and longitudinal impacts were conducted on the design concepts while mounted to a concrete culvert headwall. The resultant damage from each test was confined to post bending. Although all four designs prevented damage to the socket assembly and culvert headwall, the top-mounted, single-anchor design and the side-mounted design were recommended for use on the basis of ease of fabrication and installation. The new W-beam guardrail system for attachment to low-fill culverts was designed with multiple advantages over current culvert treatments. The guardrail system mounts to the outside face of the headwall. Thus it minimizes intrusion over the culvert and maximizes the traversable roadway width. The barrier has an unrestricted system length and does not require a transition when attached to a standard MGS. The attachment configurations were designed with epoxy anchors to enable system installment on new or existing culverts. Finally, implementation guidance was provided for new system installations.

Development and Implementation of the Simplified Midwest Guardrail System Stiffness Transition

The varied lateral stiffness between bridge rails and approach guardrail systems may cause vehicle pocketing or wheel snagging to occur near rigid bridge rail ends. To mitigate this potential hazard, an approach guardrail transition (AGT) is used to provide a gradual increase in the lateral stiffness of the barrier between the W-beam guardrail system and the bridge railing. However, these transitions can also cause a propensity for vehicle pocketing or wheel snagging if the change in lateral stiffness occurs too rapidly. Recently, a stiffness transition based on NCHRP Report 350 was developed for use with the Midwest Guardrail System (MGS) and a stiff Thrie beam AGT, and successful testing was performed close to the upstream end of the AGT. The transition was designed with three sizes of steel posts, one of which was nonstandard for state departments of transportation. Thus, a simplified version of the original MGS stiffness transition that used two common sizes of steel posts was developed and was subjected to full-scale crash testing according to Test Level 3 as set forth in the Manual for Assessing Safety Hardware. Subsequently, dynamic post properties obtained from bogie testing and numerical simulations were used to develop an equivalent wood post version of the simplified MGS stiffness transition. Recommendations are made regarding the attachment of the stiffness transitions to FHWA-accepted Thrie beam bridge rail AGTs.

Nonblocked Midwest Guardrail System for Wire-Faced Walls of Mechanically Stabilized Earth

Wire-faced walls of mechanically stabilized earth (MSE) provide an economical method for building vertical structures for supporting roadways where local topography or high land costs preclude the use of conventional fill slopes. W-beam guardrail systems are often used for shielding high vertical drop-offs associated with MSE walls. For this study, the Midwest Guardrail System (MGS) was modified to decrease the overall width of the MSE wall structure. Dynamic component testing was used to determine the post–soil behavior of steel and wood posts embedded in compacted soil materials used for constructing wire-faced MSE walls as well as to evaluate the effects of sloped terrain and different installation methods. Twenty-six dynamic tests were performed to evaluate the propensity for MSE wall damage, to select post length, and to determine the preferred post material and section. The standard MGS was modified by removing the wood spacer blocks 12 in. (305 mm) deep and by incorporating W-beam backup plates. All other MGS features—including the W6 × 8.5 (W152 × 12.6) steel posts 6 ft (1.8 m) long, rail splices at midspan locations, the 31-in. (787-mm) top-mounting height, and the 75-in. (1,905-mm) post spacing—were maintained. The nonblocked MGS was installed with the posts driven at the slope break point of a 3H:1V fill slope. The modified MGS was successfully crash tested with both 1100C small car and 2270P pickup truck vehicles in accordance with Test Level 3 safety performance guidelines in the Manual for Assessing Safety Hardware. The MSE wall was not damaged during the testing programs. The nonblocked MGS is recommended for use with wire-faced MSE walls when they are placed at the slope break point of a 3H:1V fill slope. The modified MGS reduces the required width of the MSE wall, resulting in decreased construction costs.

Midwest Guardrail System with round Timber Posts

A modified Midwest Guardrail System (MGS) was developed by using small-diameter round wood posts. The barrier system was configured with three timber species: Douglas fir (DF), ponderosa pine (PP), and southern yellow pine (SYP). Barrier VII computer simulation, combined with cantilever post testing in a rigid sleeve and soil, was used to determine the required post diameter for each species. The recommended nominal sizes were 184 mm (7.25 in.) for DF, 203 mm (8 in.) for PP, and 190 mm (7.5 in.) for SYP. A grading criterion limiting knot size and ring density was established for each species. The recommended knot sizes were limited to 38 mm (1.5 in.) or smaller for DF, 89 mm (3.5 in.) or smaller for PP, and 64 mm (2.5 in.) or smaller for SYP. The minimum ring densities equaled or exceeded 6 rings per inch (rpi) for DF, 6 rpi for PP, and 4 rpi for SYP. Two guardrail systems–-one using DF posts and another using PP posts–-were crash tested according to the Test Level 3 requirements specified in NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. Crash testing was not conducted on the SYP system because of the adequacy of previous testing on 184-mm (7.25-in.) diameter SYP posts in a standard W-beam guardrail system and post design strength comparable to that in the other two species. Both crash tests showed that the modified MGS functioned adequately for both wood species. Three round wood post alternatives were recommended as an acceptable substitute for the standard W152×13.4 (W6×9) steel post used in the MGS.

Impact performance of W-beam guardrail installed at various flare rates

The potential to increase suggested flare rates for strong post, W-beam guardrail systems and thus reduce guardrail installation lengths is investigated. This reduction in length would result in decreased guardrail construction and maintenance costs, and reduce impact frequency. If the W-beam guardrail can withstand the higher impact angles, with only modest increases in accident severity, total accident costs can be reduced. Computer simulation and five full-scale crash tests were completed to evaluate increased flare rates up to, and including, 5:1. Computer simulations indicated that conventional G4(1S) guardrail modified to incorporate a routed wood block could not successfully meet NCHRP Report 350 crash test criteria when installed at any steeper flare rates than the 15:1 recommended in the Roadside Design Guide. However, computer modeling and full-scale crash testing showed that the Midwest Guardrail System (MGS) could meet NCHRP Report 350 impact criteria when installed at a 5:1 flare rate. Impact severities during testing were found to be greater than intended, yet the MGS passed all NCHRP 350 requirements. Hence, flaring the MGS guardrail as much as 5:1 will still provide acceptable safety performance for the full range of passenger vehicles. Increasing guardrail flare rates will reduce the overall number of guardrail crashes without significantly increasing risks of injury or fatality during the remaining crashes. Therefore, it is recommended that, whenever roadside topography permits, flare rates should be increased to as high as 5:1 when using the MGS.

Numerical analysis of impact effect on mechanical behavior of strong guardrail system

The purpose of this study is to estimate the crashworthiness of a guardrail system, and to optimize the relative vertical distance between centroid of vehicle and mounting height of W-beam. Abaqus/Explicit 6.5 software is used to simulate the dynamic response of the post and W-beam guardrail systems under vehicular impacts. Numerical results of maximum displacement of vehicles during dynamic contact between vehicle and guardrail system with various given masses of vehicles are obtained. Energy-absorbing properties of the guardrail system are studied for different values of centroid height. Influence of frictional coefficient between ground surface and vehicles is also investigated.

Performance of Steel-Post, W-Beam Guardrail Systems

On the basis of the proposed changes to the NCHRP Report 350 guidelines, NCHRP Project 22-14(2) researchers deemed it appropriate to first evaluate two strong-post W-beam guardrail systems before finalizing the new crash testing procedures and guidelines. For this effort, the modified G4(1S) W-beam guardrail system and the Midwest Guardrail System (MGS) were selected for evaluation and comparison. Five full-scale vehicle crash tests were performed with the two longitudinal barrier systems, in accordance with the Test Level 3 (TL-3) requirements presented in the NCHRP Report 350 Update. For the modified G4(1S) testing program, two 2,270-kg pickup truck vehicles (2270P vehicles) were used: one 3/4-ton, two-door vehicle and one 1/2-ton, four-door vehicle. For the MGS testing program, two 2,270-kg pickup truck vehicles (2270P vehicles) and one 1,100-kg small-car vehicle (an 1100C vehicle) were used, with both pickup truck configurations being evaluated. On the basis of several findings, the NCHRP Project 22-14(2) researchers determined that the 1/2-ton, four-door pickup truck was better suited for use as a surrogate light truck test vehicle than the 3/4-ton, two-door pickup truck. The modified G4(1S) W-beam guardrail system, mounted at the top rail height of 706 mm, provided acceptable safety performance when it was crashed into by the 1/2-ton, four-door pickup truck vehicle, thus meeting the proposed TL-3 requirements presented in the NCHRP Report 350 Update. Testing of the modified G4(1S) W-beam guardrail system was not successful with a 3/4-ton, two-door pickup truck under the TL-3 impact conditions. The MGS was found to meet the TL-3 criteria presented in the NCHRP Report 350 Update for Test Designations 3-10 and 3-11. Satisfactory safety performance was observed with the MGS with both the 1/2-ton, four-door and 3/4-ton, two-door pickup truck vehicles.

Design, Development, and Qualification of New Guardrail Post

The basic design concepts for strong-post w-beam guardrail systems were developed more than 30 years ago. Although the vehicle fleet today differs significantly from vehicles for which the systems were designed, those systems are still in widespread use. One of the changes in the vehicle fleet with the most influence on the performance of guardrails and other safety barriers is the emergence of pickup trucks and SUVs. These vehicles are heavy and have relatively high centers of gravity, so in addition to overloading the guardrail, such vehicles are highly unstable during redirection and are likely to roll over. One of the most serious problems with these systems is the front impact-side wheel snagging on the guardrail posts. Conventional post types used in strong-post guardrail systems consist of either large wooden posts or steel I-beam section posts, both of which are unforgiving when impacted by a wheel. Recently, HALCO, LLC, developed the HALCO X-44 post, a guardrail post that is lightweight, strong, and designed to be used in strong-post w-beam guardrail applications as an alternative to conventional post types. The X-44 post was designed to be more forgiving when crashed into by the wheel of a vehicle, yet strong enough to limit guardrail deflection under NCHRP Report 350 Test Level 3 impact conditions. In this study the HALCO X-44 post was evaluated in a length-of-need section of w-beam guardrail. A finite element model of the guardrail system was developed, and the finite element program LS-DYNA was used to assess its performance under NCHRP Report 350 Test 3-11 impact conditions. A full-scale crash test was subsequently conducted after favorable results from the finite element analysis. The system successfully passed the safety requirements of NCHRP Report 350 for Test Level 3. This paper discusses the evaluation procedure and presents results of the HALCO X-44 post and guardrail system analysis.

Design, Development, and Qualification of New Guardrail Post

The basic design concepts for strong-post w-beam guardrail systems were developed more than 30 years ago. Although the vehicle fleet today differs significantly from vehicles for which the systems were designed, those systems are still in widespread use. One of the changes in the vehicle fleet with the most influence on the performance of guardrails and other safety barriers is the emergence of pickup trucks and SUVs. These vehicles are heavy and have relatively high centers of gravity, so in addition to overloading the guardrail, such vehicles are highly unstable during redirection and are likely to roll over. One of the most serious problems with these systems is the front impact-side wheel snagging on the guardrail posts. Conventional post types used in strong-post guardrail systems consist of either large wooden posts or steel I-beam section posts, both of which are unforgiving when impacted by a wheel. Recently, HALCO, LLC, developed the HALCO X-44 post, a guardrail post that is lightweight, strong, and designed to be used in strong-post w-beam guardrail applications as an alternative to conventional post types. The X-44 post was designed to be more forgiving when crashed into by the wheel of a vehicle, yet strong enough to limit guardrail deflection under NCHRP Report 350 Test Level 3 impact conditions. In this study the HALCO X-44 post was evaluated in a length-of-need section of w-beam guardrail. A finite element model of the guardrail system was developed, and the finite element program LS-DYNA was used to assess its performance under NCHRP Report 350 Test 3-11 impact conditions. A full-scale crash test was subsequently conducted after favorable results from the finite element analysis. The system successfully passed the safety requirements of NCHRP Report 350 for Test Level 3. This paper discusses the evaluation procedure and presents results of the HALCO X-44 post and guardrail system analysis.