Crash Impact Research Articles

항공기 비상사태에 대한 객실안전조치에 관한 연구 -객실승무원의 안전업무와 승객의 객실안전정보 인식을 중심으로-

Aircraft accidents these days, following the mega sizing trend of the aircraft, result in enormous losses of human lives apart from those of property, which cannot be replaced by any means. As most recently, in April 20, 2012, a Boeing 737 passenger plane departed Karachi on an augural flight to Islamabad, Pakistan, crashed close to an express highway on final approach, all 121 passengers and 6 crew members were killed. As such a large number of fatalities have been recorded in aircraft accidents while accident investigation results show that more than 95% of aircraft accidents are now survivable. There are three basic stages in surviving the aircraft accident: surviving the crash impact, the evacuation process and the hostile post evacuation environmental elements. These stages require the cabin crew's expeditious and appropriate actions on the basis of systematic and thorough cabin safety training in order to increase occupants' survivability, along with the passengers' preparedness. In this aspect, this paper examines the issues acting as the impediments to the passenger survival in inflight emergency situations, that are the deficiencies with cabin crew safety training, related performances and the shortcomings in passengers' knowledge on inflight safety information, leading to their inappropriate responses to emergency situations. These issues are analyzed and the root causes are identified, suggesting the resolving countermeasures.

FEM Analysis of Impact Tests for Steel Plate Concrete Panels against Scaled-Aircraft Impact

Due to the rear-face steel plate of the steel plate concrete wall (SC) is very effective in preventing the perforation and scabbing of concrete, in order to resist the impact of commercial aircraft crash, steel plate concrete structures are usually used in the design of external walls of nuclear power plants. In this paper, the simulation analysis of the impact test of 1/7.5 scaled aircraft model impacting the steel plated concrete panels is carried out by using finite element code ANSYS/LS-DYNA. The Winfrith material model (*MAT_84) in ANSYS/LS-DYNA is used to simulate the concrete. The damage profile of panels and residual velocity of aircraft engine comparisons between the simulations and tests are presented in this paper. The results indicate that the damage modes from the impact simulations are very good agreement with the experimental result. It is verified that not only the selection of the material parameters needed for the steel plated concrete wall and aircraft model but also the entire analysis method was appropriate and effective. This paper provided the effective methodology for simulation of the response of the steel plated concrete structure of nuclear power plant due to commercial aircraft crash impact.

Three Degrees of “G”s: How an Airbag Deployment Sensor Transformed Video Games, Exercise, and Dance

Three Degrees of “G”s: How an Airbag Deployment Sensor Transformed Video Games, Exercise, and Dance

회전익항공기 연료셀 충돌충격시험 Full-Scale 수치모사

항공기 연료셀은 추락 상황에서 승무원의 생존성과 직결되는 중요 구성품으로 회전익 항공기에 적용되고 있는 내충격성 연료셀은 추락시 승무원의 생존성 향상에 큰 역할을 하고 있다. 미육군은 항공기가 처할수 있는 다양한 상황에서 연료셀이 제 기능을 발휘할 수 있도록 1960년대 초부터 MIL-DTL-27422 이라는 연료셀 개발규격을 제정하여 현재까지 적용해 오고 있다. 해당 개발규격에 규정된 시험 중에서 충돌충격시험은 연료셀의 내충격 성능을 검증하는 시험으로써, 해당 시험을 통과하는 연료셀은 생존가능 충돌환경에서 화재가 발생하지 않아 승무원의 생존성이 대폭 향상될 수 있음을 의미한다. 그러나 충돌충격시험은 작용하는 하중 수준이 너무 높기 때문에 실패 위험성이 가장 큰 시험이기도 하다. 연료셀이 해당 시험을 통과하지 못하는 경우에는 재시험을 위한 비용과 준비기간이 상당히 소요되어 항공기 개발일정에 심각한 지장을 초래할 가능성도 높다. 따라서, 연료셀 설계 초기부터 내충격성능 만족여부에 대한 예측을 위해 충돌충격시험의 수치해석을 통한 실물시험에서의 실패 가능성을 최소화해야 한다는 필요성이 제기되어 왔다. 본 연구에서는 충돌모사 프로그램인 LS-DYNA에서 지원하는 유체-구조 연성해석 방법인 SPH 방법을 사용하여 연료셀 충돌충격시험 수치 모사를 수행하였다. 수치해석 조건으로 MIL-DTL-27422에서 요구하는 시험조건을 고려하였고, 실물 연료셀의 시편시험을 통해 확보한 물성데이타를 해석에 반영하였다. 그 결과로 연료셀 자체의 응력수준을 평가하고 취약부위에 대한 고찰을 수행하였다. Crashworthy fuel cells have a great influence on improving the survivability of crews. Since 1960's, the US army has developed a detailed military specification, MIL-DTL-27422, defining the performance requirements for rotorcraft fuel cells. In the qualification tests required by MIL-DTL-27422, the crash impact test should be conducted to verify the crashworthiness of fuel cell. Success of the crash impact test means the improvement of survivability of crews by preventing post-crash fire. But, there is a big risk of failure due to huge external load in the crash impact test. Because the crash impact test itself takes a long-term preparation efforts together with costly fuel cell specimens, the failure of crash impact test can result in serious delay of a entire rotorcraft development. Thus, the numerical simulations of the crash impact test has been required at the early design stage to minimize the possibility of trial-and-error with full-scale fuel cells. Present study performs the numerical simulation using SPH(smoothed particle hydro-dynamic) method supported by a crash simulation software, LS-DYNA. Test condition of MIL-DTL-27422 is reflected on analysis and material data is acquired by specimen test of fuel cell material. As a result, the resulting equivalent stresses of fuel cell itself are calculated and vulnerable areas are also evaluated.

Injury prediction in a side impact crash using human body model simulation

BackgroundImproved understanding of the occupant loading conditions in real world crashes is critical for injury prevention and new vehicle design. The purpose of this study was to develop a robust methodology to reconstruct injuries sustained in real world crashes using vehicle and human body finite element models. MethodsA real world near-side impact crash was selected from the Crash Injury Research and Engineering Network (CIREN) database. An average sedan was struck at approximately the B-pillar with a 290 degree principal direction of force by a lightweight pickup truck, resulting in a maximum crush of 45cm and a crash reconstruction derived Delta-V of 28kph. The belted 73-year-old midsized female driver sustained severe thoracic injuries, serious brain injuries, moderate abdominal injuries, and no pelvic injury. Vehicle finite element models were selected to reconstruct the crash. The bullet vehicle parameters were heuristically optimized to match the crush profile of the simulated struck vehicle and the case vehicle. The Total Human Model for Safety (THUMS) midsized male finite element model of the human body was used to represent the case occupant and reconstruct her injuries using the head injury criterion (HIC), half deflection, thoracic trauma index (TTI), and pelvic force to predict injury risk. A variation study was conducted to evaluate the robustness of the injury predictions by varying the bullet vehicle parameters. ResultsThe THUMS thoracic injury metrics resulted in a calculated risk exceeding 90% for AIS3+ injuries and 70% risk of AIS4+ injuries, consistent with her thoracic injury outcome. The THUMS model predicted seven rib fractures compared to the case occupant's 11 rib fractures, which are both AIS3 injuries. The pelvic injury risk for AIS2+ and AIS3+ injuries were 37% and 2.6%, respectively, consistent with the absence of pelvic injury. The THUMS injury prediction metrics were most sensitive to bullet vehicle location. The maximum 95% confidence interval width for the mean injury metrics was only 5% demonstrating high confidence in the THUMS injury prediction. ConclusionsThis study demonstrates a variation study methodology in which human body models can be reliably used to robustly predict injury probability consistent with real world crash injury outcome.

SAFETY MARGINS OF SPENT FUEL TRANSPORT AND STORAGE CASKS CONSIDERING AIRCRAFT CRASH IMPACTS

AbstractThe safety of spent fuel transport casks in severe accident conditions is always a matter of concern. This paper surveys German missile impact tests that have been carried out in the past to demonstrate that German cask designs for transport and interim storage are safe even under conditions of an aircraft crash impact. A fire test with a cask beside an exploding propane vessel and temperature calculations concerning prolonged fires also show that the casks have reasonably good safety margins in thermal accidents beyond regulatory fire test conditions.

Aortic injuries in newer vehicles

The occurrence of AI was studied in relation to vehicle model year (MY) among front seat vehicular occupants, age≥16 in vehicles MY≥1994, entered in the National Automotive Sampling System Crashworthiness Data System between 1997 and 2010 to determine whether newer vehicles, due to their crashworthiness improvements, are linked to a lower risk of aortic injuries (AI). MY was categorized as 1994–1997, 1998–2004, or 2005–2010 reflecting the introduction of newer occupant protection technology. Logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals for the association between AI and MY independent of possible confounders. Analysis was repeated, stratified by frontal and near lateral impacts. AI occurred in 19,187 (0.06%) of the 31,221,007 (weighted) cases, and contributed to 11% of all deaths. AIs were associated with advanced age, male gender, high BMI, near-side impact, rollover, ejection, collision against a fixed object, high ΔV, vehicle mismatch, unrestrained status, and forward track position. Among frontal crashes, MY 98–04 and MY 05–10 showed increased adjusted odds of AI when compared to MY 94–97 [OR 1.84 (1.02–3.32) and 1.99 (0.93–4.26), respectively]. In contrast, among near-side impact crashes, MY 98–04 and MY 05–10 showed decreased adjusted odds of AI [OR 0.50 (0.25–0.99) and 0.27 (0.06–1.31), respectively]. While occupants of newer vehicles experience lower odds of AI in near side impact crashes, a higher AI risk is present in frontal crashes.

Influence of vehicle secondary impact following an emergency braking on an unbelted occupant's neck, head and thorax injuries

Passive safety has for many years reduced the number of fatalities on the roads. However, its effect on occupants’ safety has now stabilised, meaning that new active safety features are needed to reduce further the number of casualties. These active safety features, like autonomous emergency braking (AEB), aim to prevent vehicle collisions and reduce the vehicle kinetic energy on impact. A previous study has shown that unbelted occupants kinematics are affected by the pre-braking phase, suggesting that the occupant's hand positions on the steering wheel, combined with a bracing behaviour, could cause the occupant to miss the deploying airbag in the case of a secondary rigid wall impact. This paper will investigate the variations of the secondary vehicle impact crash patterns by calculating crash pulses based on typical vehicle frontal accident scenarios and conclude on these effects on the human occupant's neck, head and thorax injuries.

Crew and Patient Safety in Ambulances: Results of a Personnel Survey and Experimental Side Impact Crash Test

Ambulance drivers often travel under stressful conditions at high speed while using vehicles with poor high-speed maneuverability. The occupant safety of ambulance vehicles has not yet been addressed by the automotive safety paradigm; particularly for the rear patient compartment. This study had two objectives: (1) to assess by survey the French Emergency Medical Services (EMS) to determine the layout of the vehicle most often used and the EMS personnel's behavior during transport; and (2) to conduct a crash test to analyze the injuries which may affect EMS personnel and patients in the rear patient compartment. Firstly, a survey was distributed to the 50 largest metropolitan French EMS programs. Secondly, a crash test was performed with a Mobile Intensive Care Unit (MICU) in conditions closest to reality. Forty-nine of the 50 biggest metropolitan French EMS programs responded to the survey. This represents 108 French MICUs. During the last three years, 12 of 49 EMS programs (24%) identified at least one accident with an MICU, and six of these 12 (50%) suffered at least one death in those accidents. A crash test using a typical French EMS MICU showed that after impact of a collision, the ambulance was moved more than five meters with major consequences for all passengers. A study-approved human cadaver placed in the position of a potential patient was partially thrown from the stretcher with a head impact. The accelerometric reaction of the anthropomorphic manikin head was measured at 48G. The crash test demonstrated a lack of safety for EMS personnel and patients in the rear compartment. It would be preferable if each piece of medical equipment were provided with a quick release system resistant to three-dimensional 10G forces. The kinetic changes undergone by the "patient" substitute on the stretcher would probably have an effect of causing injury pathology. This study highlights the need for more research and development in this area.

Fatigue Fracture of a Compressor Disc of an Aeroengine

There was an accident to a single engine aircraft. From the eye and ear witness accounts, it was established that the accident occurred because of engine failure. After preliminary examination of the wreckage of the crashed engine, a few suspected components were identified for detailed laboratory investigation. The objective was to establish the primary failure in the engine. While majority of the engine components submitted for laboratory analysis showed secondary damages due to either crash impact forces or post-accident fire, the fracture pattern in one of the compressor disks was different from other components of the engine. Fractographic study revealed that the failure of the disk was by fatigue mechanism. Subsequent investigation showed that the fatigue fracture of the compressor disk was the first in the chain of events that led to the engine failure. This finding was further substantiated through fracture mechanics calculations.

회전익항공기용 연료셀 Phase II 인증시험에 대한 고찰

회전익항공기 연료셀은 추락시 승무원의 생존성과 직결되는 구성품이다. 1950년대부터 미육군에서는 연료셀에 적합한 특성을 갖는 소재를 개발하기 위해 다양한 노력을 기울여왔다. 그 결과로 1961년에 MIL-T-27422A라는 항공기용 연료셀 설계규격이 처음 등장하였고, 수회의 개정을 거쳐 2007년 MIL-DTL-27422D라는 미군사 규격으로 발전되었다. 미군사 규격은 항공기용 연료셀 개발에서 가이드라인 되고 있는 중요한 지침서로써, 연료셀이 항공기에 장착되기 위해서는 사전에 규정된 인증시험을 통해 성능입증이 완료되어야 한다. 인증시험은 소재의 성능입증과 관련된 Phase I, 연료셀 자체의 성능입증과 관련된 Phase II 로 구분된다. 본 논문에서는 Phase II 인증시험 중 가장 중요하면서 실패 위험성이 큰 항목으로 평가되고 있는 슬로싱 및 진동시험, 내탄시험, 충돌충격시험에 대한 수행 절차 및 시험조건에 대해 살펴보고, 각 시험의 조건 및 절차에 대한 논리적 근거를 고찰하였다. 이러한 인증시험의 논리적 고찰은 인증시험 절차의 적절성과 시험 결과에 대한 합리적 판단 능력을 향상시켜 항공기 개발에 있어서 향후 보다 체계적인 개발이 가능해 질 것으로 사료된다. Fuel tank of a rotorcraft has a great influence on the survivability of crews. For a long time, US army has tried to develop the proper material for fuel cell of a military rotorcraft. As a result, the design specification of fuel cell, MIL-T-27422A, was issued for the first time on 1961. Through a few revisions, it has been developed to ML-DTL-27422D in 2007. It should be assured that fuel cell satisfies the requirement defined in MIL-DTL-27422D. The qualification test of this specification is classified into Phase I test for material and Phase II for fuel cell itself. This paper studies test conditions and procedures of slosh & vibration, gunfire resistance and crash impact test. They are considered as the most important tests which have a high possibility of failure. The rational consideration of this paper can improve the ability for estimating not only the validity of test procedure and test condition but test result. Based on the rational consideration, it is expected that the ability of the systematic development can be improved.

Finite element analysis of occupant head injuries: Parametric effects of the side curtain airbag deployment interaction with a dummy head in a side impact crash

In this study, we investigated and assessed the dependence of dummy head injury mitigation on the side curtain airbag and occupant distance under a side impact of a Dodge Neon. Full-scale finite element vehicle simulations of a Dodge Neon with a side curtain airbag were performed to simulate the side impact. Owing to the wide range of parameters, an optimal matrix of finite element calculations was generated using the design method of experiments (DOE); the DOE method was performed to independently screen the finite element results and yield the desired parametric influences as outputs. Also, analysis of variance (ANOVA) techniques were used to analyze the finite element results data. The results clearly show that the influence of moving deformable barrier (MDB) strike velocity was the strongest influence parameter on both cases for the head injury criteria (HIC36) and the peak head acceleration, followed by the initial airbag inlet temperature. Interestingly, the initial airbag inlet temperature was only a ~30% smaller influence than the MDB velocity; also, the trigger time was a ~54% smaller influence than the MDB velocity when considering the peak head accelerations. Considering the wide range in MDB velocities used in this study, results of the study present an opportunity for design optimization using the different parameters to help mitigate occupant injury. As such, the initial airbag inlet temperature, the trigger time, and the airbag pressure should be incorporated into vehicular design process when optimizing for the head injury criteria.

Causation and outcomes of diaphragmatic injuries in vehicular crashes

This study aimed to identify vehicular and crash factors associated with diaphragmatic injuries (DIs). DI presence was analyzed among Crash Injury Research and Engineering Network vehicular occupants (age ≥ 16 years) in relation to occupant and crash factors. Contact points (i.e., components in direct contact with occupants) involved in injury causation were analyzed. Cases with and without DI were compared in relation to mortality, Injury Severity Score (ISS) and the occurrence of injuries with a maximum Abbreviated Injury Scale (MAIS) score of 3+. Student's t test, Wilcoxon test, χ(2), and multiple logistic regression were used for statistical analysis. Of a total of 2,344 cases with complete data for analysis, 80 cases (3.4%) experienced DI. Multiple logistic regression analysis revealed a significant association with the occurrence of DI for near lateral impact (odds ratio, 7.71 [4.20-14.58]) and change in velocity (ΔV) of 40 km/h or greater (odds ratio 2.58 [1.29-5.24]). The seat belt and steering wheel were the most common contact points among frontal impact crashes, and the side interior surface and side hardware or armrest were the more common contact points among side impact crashes. DI cases experienced more MAIS3+ injuries in the head, chest and abdominal regions and exhibited higher median ISS (q1-q3) [42 (29-62.5) vs. 17 (10-27), p < 0.0001]. While mortality was higher among occupants with DI (48% vs. 14%), this effect disappeared when adjusted by ISS. DI are associated with lateral crashes and higher ΔV. Head, chest, and abdominal injuries occur more commonly among DI patients, and the presence of these injuries rather than the DI itself is responsible for the increased mortality in these patients. Epidemiologic study, level III.

Evaluation of vehicle side airbag effectiveness in Victoria, Australia

Side airbag systems were first introduced into vehicles around 1995 to help protect occupants from injury in side impact crashes. International studies have shown that side airbags are effective in reducing the risk of death and injury, however, serious injuries can still occur even when side airbags deploy. The objective of this study was to use detailed injury information from insurance injury compensation claims data linked to Police reported crash data to determine the effectiveness of side airbags in reducing the risk of death or injury for occupants involved in side impact crashes in Victoria, Australia based on the specific body regions that side airbag systems are designed to protect. It was found that head and torso-protecting dual airbag systems designed to protect the head, neck, face, chest and abdomen are highly effective in reducing driver death or injury due to near side crashes. They were associated with a statistically significant reduction of 41.1% (25.9%, 53.2%) in the odds of death or injury across all body regions; and a 48.0% (28.0%, 62.4%) reduction in the odds of death or injury to the head, neck, face, chest and abdomen. The study did not find any evidence that torso-protecting airbags alone are effective in reducing death or injury. Analysis results indicate that head and torso-protecting side airbag systems in vehicles are a highly effective technology for reducing the risk of death or injury to vehicle occupants in near side crashes. The magnitude of the injury reduction benefits estimated indicate that fitment of this technology to all vehicles should be a high priority and will yield significant savings in overall road trauma.

Crashworthiness Determination for Front and Rear Doors and B Pillar Subjected to Side Impact Crash by a Mobile Deformable Barrier

In Euro NCAP standard, adult protection is one of the most important rating scores with 50% weight factor while child protection and pedestrian protection are accounted into consideration with 20% weight factor. For adult protection testing, three tests are required to perform: (1) side impact, (2) pole impact, (3) front impact. In the side impact test, dummy's head, chest, shoulder, thorax, ribs, abdomen, pelvic and femur must be studied to evaluate the rating score. Crashworthiness of a car during side impact can describe the score rated for that car. In this paper the goal is to determine the crashworthiness of side doors and B-pillar in side impact crash test by simulation using LS DYNA software in order to predict required changes to achieve 5 star rating. A model of car has been developed using Hypermesh and CATIA software. A mobile deformable barrier (MDB) model and its honey comp area have been prepared with respect to ECE R95 and Euro NCAP standard. Initial condition such as velocity has been assigned to MDB. Results show that improvement in design in order to increase absorbed energy can probably has positive effect on crash performance as good as using side air bag in order to achieve 5 star rating.

Effect of Material and Thickness of Side Doors and B Pillar on Crashworthiness in Euro NCAP Side Impact Crash Test

In side impact test which is one out of three tests of Euro NCAP standard, front and rear doors and B pillar are most absorbance parts among vehicle body parts. Passengers are highly in danger while side crash, because of the distance between passenger's head and vehicle body. In this paper effect of material and thickness of doors and B-pillar and their absorbed energy during crash and improvement of its crashworthiness with respect to light weight design are studied using LS DYNA solver. The objective of this paper is to propose a material for doors and B-pillar with a specified thickness to achieve maximum absorbed energy and minimum weight. The shape of the doors and B-pillar remains unchanged and its effect on crashworthiness was not investigated. Parameters which could be changed were material and thickness. Material which studied were steel AISI 1006, aluminum alloy 5182, magnesium AZ31B and high strength steel 204M. For each selected material, five thicknesses were considered and the same initial and boundary conditions according to NCAP were applied. Results show that decreasing in thickness of these parts do not always increase the absorbed energy. In order to reduce the weight and increase the total absorbed energy the best way is to use thinner parts with light material and use a reinforcement bar or foam inside the doors.

Effect of Material on Crashworthiness for Side Doors and B Pillar Subjected to Euro NCAP Side Impact Crash Test

Investigation in effects of material of vehicle body on crashworthiness by simulation methods helps researches to overcome on practical problems of crash test such as die making, long period of test preparation and financial issues. In this paper the goal is to find out the effect of four proposed material on crashworthiness of side doors and B pillar in Euro NCAP side impact test. Materials have been assigned to side doors and B pillar in vehicle model by using LS DYNA pre/post soft ware. Results obtained using LS DYNA post processing by applying Euro NCAP initial conditions. Results show that the best material among mentioned materials for B pillar which can be propose is AISI1006 and best material for side doors is strength steel 204M.

Identifying Primary and Secondary Crashes from Spatiotemporal Crash Impact Analysis

The identification of secondary crashes is accompanied by the definition of the primary crash impact area. Although the crash impact area varies with the geometric characteristics of roads and periodic characteristics of traffic flow as well as with crash type, most previous studies have used a fixed boundary to identify secondary crashes and primary crashes. Thus, the objective of this research is to develop a method to define the spatiotemporally different boundaries varying with different types of crash. On the basis of the developed boundaries, the secondary crash is identified in the primary crash location as well as in its opposite direction. Secondary crashes in the same and opposite directions are identified to be 7.4% and 3.8% of total primary crashes, respectively. Also, only 0.3% of total primary crashes are connected with the secondary crash in both the same and the opposite directions. Although the proposed method seems to be complicated, the results will be useful in understanding secondary crash characteristics in a more realistic analysis through the spatiotemporal crash impact area in the crash direction as well as in the opposite direction. Specifically, the results can be used by public-sector transportation agencies in making operational strategies for reducing secondary crashes on freeways.

The Repeatability and Reproducibility of the BioRID IIg in a Repeatable Laboratory Seat Based on a Production Car Seat

Objective: The United Nations Economic Commission for Europe Informal Group on GTR No. 7 Phase 2 are working to define a build level for the BioRID II rear impact (whiplash) crash test dummy that ensures repeatable and reproducible performance in a test procedure that has been proposed for future legislation. This includes the specification of dummy hardware, as well as the development of comprehensive certification procedures for the dummy. This study evaluated whether the dummy build level and certification procedures deliver the desired level of repeatability and reproducibility. Methods: A custom-designed laboratory seat was made using the seat base, back, and head restraint from a production car seat to ensure a representative interface with the dummy. The seat back was reinforced for use in multiple tests and the recliner mechanism was replaced by an external spring–damper mechanism. A total of 65 tests were performed with 6 BioRID IIg dummies using the draft GTR No.7 sled pulse and seating procedure. All dummies were subject to the build, maintenance, and certification procedures defined by the Informal Group. Results: The test condition was highly repeatable, with a very repeatable pulse, a well-controlled seat back response, and minimal observed degradation of seat foams. The results showed qualitatively reasonable repeatability and reproducibility for the upper torso and head accelerations, as well as for T1 Fx and upper neck Fx . However, reproducibility was not acceptable for T1 and upper neck Fz or for T1 and upper neck My . The Informal Group has not selected injury or seat assessment criteria for use with BioRID II, so it is not known whether these channels would be used in the regulation. However, the ramping-up behavior of the dummy showed poor reproducibility, which would be expected to affect the reproducibility of dummy measurements in general. Pelvis and spine characteristics were found to significantly influence the dummy measurements for which poor reproducibility was observed. It was also observed that the primary neck response in these tests was flexion, not extension. This correlates well with recent findings from Japan and the United States showing a correlation between neck flexion and injury in accident replication simulations and postmortem human subjects (PMHS) studies, respectively. Conclusions: The present certification tests may not adequately control front cervical spine bumper characteristics, which are important for neck flexion response. The certification sled test also does not include the pelvis and so cannot be used to control pelvis response and does not substantially load the lumbar bumpers and so does not control these parts of the dummy. The stiffness of all spine bumpers and of the pelvis flesh should be much more tightly controlled. It is recommended that a method for certifying the front cervical bumpers should be developed. Recommendations are also made for tighter tolerance on the input parameters for the existing certification tests.

Safety Evaluation of Discontinuing Late Nighttime Flash Operations at Signalized Intersections

This study examined the safety impacts of converting late nighttime flash operation to normal phasing operation at signalized intersections by using the empirical Bayes, the univariate full Bayes, and multivariate full Bayes before-and-after methods. Data were obtained from the North Carolina Department of Transportation for 61 treatment sites and 395 reference intersections that remained on late nighttime flash operation from 2000 to 2007. The results from the empirical Bayes method are almost identical to those of the univariate full Bayes. The full Bayes method offered more flexibility in selecting the functional form of expected crashes at similar sites (similar to the safety performance function in the empirical Bayes) and in addressing uncertainty in the data. Compared with the univariate full Bayes, the multivariate full Bayes with the multivariate Poisson lognormal (MVPLN) model provided better results based on much lower deviance information criterion values. The MVPLN model was favored and the recommended crash reduction factors are 48% (±6%), 53% (±8%), and 57% (±7%) for nighttime total, injury and fatal, and frontal impact crashes, respectively.