Length Of Need Research Articles

Manual for Assessing Safety Hardware TL-4 Evaluation of Critical Flare Rate for Cast-in-Place Concrete Barrier

Concrete median barriers are used by Departments of Transportation (DOTs) to provide separation of traffic. Typically, the crashworthiness of these barriers is tested and evaluated in full-scale crash testing conducted according to current roadside safety device standards. Occasionally, DOTs need to flare the concrete barrier length of need (LON) around fixed objects, such as bridge piers. Flaring a concrete barrier increases the effective impact angle which consequently increases the impact severity of the vehicle creating an opportunity for vehicle instability or excessive occupant risk factors. No current recommendations are available to guide the installation of flared barriers around such fixed objects, while still maintaining barrier crashworthiness. Although the current practice is to flare the cast-in-place (CIP) concrete barrier at a maximum 20:1 rate, no full-scale crash testing has been conducted to determine the crashworthiness of the system at this condition or at a flare rate that might be considered more critical. The crash tests reported in this paper were performed according to the Manual for Assessing Safety Hardware (MASH) Tests 4–10 (with the use of a passenger car), 4–11 (a pickup truck), and 4–12 (a single unit truck) for LON, which represent the tests considered necessary to demonstrate the MASH compliance of the device. The 40-in. single slope CIP concrete barrier with a 20:1 flare rate met MASH requirements and is considered MASH compliant for Test Level (TL) 4. The system is considered suitable for implementation where there is a need to flare the concrete barrier around a fixed object.

Development, Crash Testing, and Evaluation of Portable Concrete Barriers Gap-Spanning Hardware

Portable concrete barriers (PCBs) are commonly used to protect work-zone personnel and to shield motorists from hazards in construction areas. It is not uncommon to encounter longitudinal gaps within PCB installations resulting from the practice of constructing and connecting the barriers from different ends during setup or contractor operations. Longitudinal gaps can also be created by tensioning issues following an impact event. These gaps can range from 6 in. to a full barrier segment length of 12.5 ft. Longitudinal gaps between adjacent installations of PCB systems pose a serious safety concern for the errant motorist. Therefore, a need existed to develop a treatment capable of shielding the longitudinal gaps that occur between adjacent installations of PCB systems. In this research, design concepts for the gap-spanning hardware were conceived, and two design concepts were selected for further investigation and refinement through LS-DYNA computer simulation. Based on simulation results and input from the Midwest Pooled Fund Program member states, the design concept utilizing nested thrie-beam spanning the gap was chosen for full-scale crash testing under Manual for Assessing Safety Hardware 2016 (MASH 2016). Two tests were conducted to MASH test no. 3-11 to evaluate the length of need of the system, as well as the transition from the gap-spanning hardware to the PCBs. In both tests, the 2270P vehicle was contained and safely redirected. Recommendations are provided for system implementation and future installation with current PCB systems.

Corridor-Based Procedure for Determining Longitudinal Barrier Length of Need

Determining the optimal length of need (LON) to prevent vehicles from striking roadside hazards is an important part of roadside design. Although barriers can provide significant safety benefits by preventing run-off-road (ROR) crashes, the barrier itself presents a small but nonzero risk of serious injury or fatality. The purpose of this study is to present a method for quantifying the protection of barrier LON using departure corridors developed with NCHRP 17-43 data. Based on real-world ROR crash trajectories from the NCHRP 17-43 database, departure corridors were constructed. This study focused on a subset of 171 crashes on roads with a speed limit between 60 and 80 km/h with a reconstructed impact speed. In these crashes, the vehicle trajectory was interrupted by either a collision or a rollover. Our approach was to extrapolate the trajectory that could have been followed by the vehicle had the collision not occurred. The original trajectory data were retained before impact and extrapolated after impact using a linear fit. These corridors incorporated the effects of hazard location, departure side, and barrier location on the runout length. Left-side departures required a longer LON to intercept the same proportion of crashes. The runout length needed for objects close to the road based on the corridor method was much smaller than the length recommended by the 2011 Roadside Design Guide. The benefit of this corridor-based approach to barrier placement is that each agency can balance barrier length and the proportion of encroachments intercepted depending on their priorities.

COVID-19: The Shift From Clinical to Public Health Ethics.

COVID-19: The Shift From Clinical to Public Health Ethics.

A nationwide survey on the use of heated humidified high flow oxygen therapy on the paediatric wards in the UK: current practice and research priorities

BackgroundHeated Humidified High Flow Nasal Cannula Oxygen Therapy (HHFNC) is increasingly used on the paediatric wards and High Dependency Units (HDU) for different types of pathologies and different age groups. We aimed to describe current practice related to the use of HHFNC on the paediatric wards and HDUs, weaning practices and preferred outcome measures for future research.MethodsWe carried out a cross-sectional online survey of UK paediatric consultants or their delegates working on the paediatric wards. Descriptive analysis of their geographical, and organizational characteristics, their specialties, and their level of experience was investigated. Reasons for HHFNC initiation, weaning criteria, patients’ characteristics and their primary pathologies were also analysed.ResultsParticipation of 218 paediatricians from 81 hospitals (Median: 2.7, Range: 1–11) was registered. HHFNC was provided in most of the surveyed hospitals (93%, 75/81). A High Dependency Unit (HDU) was available in 47 hospitals (58%); less than a third of those have a dedicated paediatrician. Decisions around HHFNC were made solely by paediatricians in (75%) of the cases, mostly at hospitals with no HDU compared to those with dedicated HDUs (70.3% VS 36.6, 95%CI:22.6–50.4%, P < .001). HHFNC was reported by nearly two-thirds (68%) of the practitioners who used it on the wards to be as effective or superior to CPAP (Continuous Positive Airway Pressure) with fewer complications. Failure rate while on HHFNC was identified as the most important outcome measure in any future research followed by the length of need for HHFNC support (37.1, and 28% respectively).ConclusionThis survey showed support for developing paediatric-specific national guidance on the use of HHFNC on the wards. Our list of defined research priorities may help guide further collaborative research efforts in this field.

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.

Improved method for roadside barrier length of need modeling using real-world trajectories

The 2011 AASHTO Roadside Design Guide (RDG) contains perhaps the most widely used procedure for choosing an appropriate length of need (LON) for roadside barriers. However, this procedure has several limitations. The procedure uses a highly simplified model of vehicle departure, and the procedure does not allow designers to specify an explicit level of protection. A new procedure for choosing LON that addresses these limitations is presented in this paper. This new procedure is based on recent, real-world road departure trajectories and uses this departure data in a more realistic way. The new procedure also allows LON to be specified for a precisely known level of protection – a level which can be based on number of crashes, injury outcomes or even estimated crash cost – while still remaining straightforward and quick to use like the 2011 RDG procedure.In this analysis, the improved procedure was used to explore the effects of the RDG procedure’s assumptions. LON recommendations given by the 2011 RDG procedure were compared with recommendations given by this improved procedure. For 55mph roads, the 2011 RDG procedure appears to lead to a LON sufficient to intercept between 80% and 90% of right-side departures that would otherwise strike a hazard located 10m from the roadway. For hazards closer than 10m, the 2011 RDG procedure intercepts progressively higher percentages of real-world departures. This suggests the protection level provided by the 2011 RDG procedure varies with the hazard offset, becoming more conservative as the hazard moves closer to the roadway. The improved procedure, by comparison, gives a consistent protection level regardless of hazard location.

SB2등급 연성베리어의 충돌지점(CIP)에 대한 연구

PURPOSES : The impact performance of flexible barrier system such as structural response, vehicular motion and occupant safety vary depending on the impact point. Thus, to properly evaluate the performance of a flexible barrier system, impact should be made to a point which will lead to the worst possible results. This point is called the Critical Impact Point (CIP). This paper presents the way to determine the CIP for a SB2 class flexible barrier system which is consisted of Thrie-Beam rail and circular hollow tube post of 2m span. METHODS: Barrier VII simulations were made for impact points; Case 1 at a post, Case 2 at 1/3 span downstream from a post, Case 3 at middle of the span, Case 4 at 2/3 span downstream from a post. For the structural performance (deflections), impact simulation of 8000kg-65km/h-15degree was used, and for vehicle motion and occupant safety, simulation of 1300kg-80km/h-20degree impact was made and analysed. RESULTS: Case 1 gave the largest dynamic deflection of 75.72cm and also gave the largest snag value of 44.3cm. Occupant safety and exit angle of the vehicle after the impact were not sensitive to the impact point and were all below the allowable limit. CONCLUSIONS : For the SB2 class flexible barrier system's CIP can be regarded as a post which is sufficiently away from the end of Length of Need in order to avoid the end-effect of the barrier system. It can be more economic in the long run because the normal concrete pavement material is likely to cost more due to higher probability of maintenance and repair and higher social cost due to traffic accident, etc.

Dynamic Evaluation and Implementation Guidelines for a Nonproprietary W-Beam Guardrail Trailing-End Terminal

Most state departments of transportation use simple adaptations of crashworthy guardrail end terminals, which typically include breakaway posts and an anchor cable, for downstream anchorage systems. The guardrail safety performance for vehicular impacts occurring in close proximity to these simplified, downstream anchorage systems is not well known. Further, the length of need (LON) for the downstream end of these systems has yet to be adequately determined. This research project assessed the safety performance of the Midwest Guardrail System (MGS) for impacts occurring in close proximity to a nonproprietary, trailing-end guardrail terminal under the Test Level 3 conditions of the Manual for Assessing Safety Hardware. The two research objectives were to (a) determine the end of the LON for impacts with light pickup trucks and (b) investigate potential risks for a small passenger car to become unstable when striking the downstream end of the MGS anchored by the nonproprietary, trailing-end terminal. Numerical simulations were carried out to identify the most critical impact location for the 1100C small car and the end of the LON for the 2270P pickup truck. In full-scale crash tests, considerable snag of the 1100C vehicle occurred; however, occupant risk values and vehicle stability were within acceptable limits. The crash test with the 2270P pickup indicated that the end of the LON was located at the sixth post from the downstream-end post. Guidelines were proposed for installing the MGS to shield hazards in close proximity to the tested nonproprietary, trailing-end terminal.

Termination and Anchorage of Temporary Concrete Barrier

The research study described herein developed an economical method for terminating and anchoring the upstream end of temporary concrete barrier systems. The termination and anchorage system was designed for use with the Kansas F-shape temporary concrete barrier design that is currently used by several states participating in the Midwest Pooled Fund Program. These efforts were performed in accordance with the Test Level 3 guidelines found in the Manual for Assessing Safety Hardware 2008. Criteria governing the design of the termination and anchorage system included development of adequate anchor loads over a finite deflection in order to limit peak loads, mitigation of vertical rotation and tipping of the end barrier about its longitudinal axis, and employing existing roadside safety hardware in the design to limit state hardware inventories. The termination and anchorage system allowed for a significant reduction in the number of barrier segments required upstream from the length of need and for use in anchoring a free-standing TCB system. The anchorage system was configured to effectively constrain the end of the TCB system for impacts as far upstream as the first anchored barrier segment. Full-scale crash testing demonstrated that the impacting vehicle was safely and smoothly redirected, and the test was judged acceptable according to the Test Level 3 safety criteria set forth in the Manual for Assessing Safety Hardware 2008.

Fostering a New Era of Vascular Access Device Selection in Neonates

Admission into the neonatal intensive care unit entails placement of multiple monitoring systems and lifelines for therapy. A vascular access device is essential to survival for most patients in the neonatal intensive care unit. Identifying the most appropriate device to meet an infant's current and anticipated infusion needs has historically focused on length of need rather than on other equally important indicators. Using this aged criterion has contributed to the exhaustion of the peripheral veins. Using a timely approach to vascular access device needs ensures early and timely placement. Providing education and ensuring the competence of staff who make decisions regarding device placement and care are warranted and lead to the prevention of complication-induced costly litigation. The goal of infusion therapy is to complete the delivery of required solutions and medications by avoiding device-related complications. Using the fewest number of devices and targeting placement of the best device to meet a patient's needs early in the course of therapy are paramount.

Design and Development of Steel Breakaway Posts

The current generation of NCHRP Report 350-compliant guardrail terminals all use wooden breakaway posts in the terminal section. The first two end posts are typically breakaway cable terminal posts inserted into steel foundation tubes that are joined with a ground strut to provide the anchorage capacity. Wood is readily available and inexpensive, but it also has many drawbacks. The quality of the wood and the associated breaking forces vary widely. The strength of a wooden post is affected by many factors, including post size, ring density, knot location and size, cracks and checks, species, and moisture content. Results are presented of an effort to design and develop steel breakaway posts for guardrail terminals. The breakaway steel post system described has been successfully tested for use in a tangent terminal. The post exhibited consistent strength for redirection impacts and failed at very low loads during head-on impacts. The breakaway steel post actually improved the redirective performance of the SKT-350 during a 2020-kg (4,450-lb) pickup truck impact at the beginning of the length of need. These breakaway steel posts have been shown to meet NCHRP Report 350 performance criteria and should provide highway agencies with an alternative where wood posts are unacceptable.

Guardrail Runout Lengths Revisited

The guardrail runout length recommendations contained in AASHTO's Roadside Design Guide were reevaluated to determine optimal guardrail length of need. Encroachment data collected along Canadian highways were evaluated in a manner similar to that used with other encroachment data to reproduce the procedures contained in AASHTO's Roadside Design Guide. A cost-benefit analysis of extending guardrails was also conducted as an alternative procedure for defining appropriate guardrail runout lengths. Both analysis procedures indicate that the guardrail runout lengths recommended by the Roadside Design Guide are excessive. Highway agencies are advised to select one of the two new procedures for identifying appropriate guardrail runout lengths.