• Proceedings of the KSR Conference
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• 2004.06a
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• pp.732-737
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• 2004

TTX(Tilting Train Express), which has improved traveling performance on curved track, is being designed in cope with future railway circumstance. Nowadays, in the world, many efforts are focussed on railway safety. Especially, a variety of researches on train crashworthiness have been conducted. As a part of these efforts, some equipments on TTX are designed to reduce fatalities and casualties in crash accidents. This paper introduces impact energy absorbtion characteristics on the initial design of the front end structure. Some comments are made briefly for improvement of initial structural design and future following researches.

• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.180-191
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• 2001

The widely used spot welded sections of automobiles(hat and double hat shaped section members) absorb most of the energy in a front-end collision. The sections were tested with respect to axial static(10mm/min) and quasi-static(1000mm/min) loads. Based on these test results, specimens with various thicknesses, width ratios and spot weld pitches on the flange were tested at high impact velocity(7.19m/sec and 7.94m/sec) which simulates an actual car crash. Characteristics of collapse have been reviewed and structures for optimal energy absorbing capacity is suggested.

• Laser Solutions
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• v.5 no.2
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• pp.23-29
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• 2002

As automotive manufacturers have taken a growing more interest in tailored sheet metals for improving the rigidity, weight reduction, crash durability, and cost saving application of the tailored sheet metals to automotive bodies has been resently increased greatly. In this study, we investigated the characteristics of fatigue crack initiation behavior of laser welded sheet use for vehicle body panel. We experimented three types of specimens which were machined of the same base metal : one is 1.4㎜ thick, another is 1.6㎜ thick, the others is laser welded of the 1.4mm thick specimen and 1.6㎜ thick specimen. The results indicated that laser welded metal (1.4＋1.6㎜) is the best one for fatigue strength and fatigue life.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.360-363
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• 2007

This paper deals with the dynamic tensile characteristics of the steel sheets for structural members of a train. Train accidents occurs rarely but lead to many casualties and economical loss. Therefore the safety of the train becomes important during the train crash. The dynamic tensile characteristics of the steel sheets are indispensable to analyze the structural crashworthiness. Current research reports the stress-strain curves, fracture elongation and strain rate sensitivities evaluated at the various strain rates especially for SUS304L-ST and SUS304L-LT steel sheets. The results include the difference in the dynamic tensile characteristics of both rolling and transverse directions. Dynamic tensile tests were performed at the strain rates ranging from 0.003/sec to 200/sec using High Speed Material Testing Machine. The materials tested in this research shows interesting behavior at the low strain rates. The strain hardening exponent decreases remarkably while the yield strength increases.

• Journal of the Ergonomics Society of Korea
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• v.36 no.2
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• pp.157-168
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• 2017

Objective: This study aims to understand the motorcycle accident characteristics of food delivery workers and to present basic guidelines on accident prevention through accident. Background: It is known that food delivery workers have a high ratio of self-employed and youth workers, and occupations with frequent disasters. Therefore the occupation is known to really be in need of accident prevention policy. Method: This study analyzed the data of motorcycle crashes of 1,310 food delivery workers that have been approved as on-duty industrial crashes since 2015. The accident characteristics were examined by dividing them into driver related factors and accident related factors. Results: Among the motorcycle crashes of food delivery workers, 99.2% of the victims were males, 82.6% had less than six months of work experience. 76.2% of the victims were employed by the companies with less than five workers. In addition, there was a difference in accident characteristics according to age, type of cuisine, accident time of the day, injured organs and injured body part. Conclusion: The results of this study can be used as baseline data to devise systematic measures to prevent motorcycle crashes of food delivery workers. Application: Preventative measures for novice young part time workers including safety education/training need to be established.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5585-5593
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• 2014

This study tested the hypothesis that the significance of the heterogeneous dispersion parameter in safety performance function (SPF) used to estimate the expected crashes is affected by the endogenous heterogeneous prior distributions, and analyzed the impacts of the mis-specified dispersion parameter on the evaluation results for traffic safety countermeasures. In particular, this study simulated the Poisson means based on the heterogeneous dispersion parameters and estimated the SPFs using both the negative binomial (NB) model and the heterogeneous negative binomial (HNB) model for analyzing the impacts of the model mis-specification on the mean and dispersion functions in SPF. In addition, this study analyzed the characteristics of errors in the crash reduction factors (CRFs) obtained when the two models are used to estimate the posterior means and variances, which are essentially estimated through the estimated hyper-parameters in the heterogeneous prior distributions. The simulation study results showed that a mis-estimation on the heterogeneous dispersion parameters through the NB model does not affect the coefficient of the mean functions, but the variances of the prior distribution are seriously mis-estimated when the NB model is used to develop SPFs without considering the heterogeneity in dispersion. Consequently, when the NB model is used erroneously to estimate the prior distributions with heterogeneous dispersion parameters, the mis-estimated posterior mean can produce large errors in CRFs up to 120%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.32-38
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• 2020

This study examined the problems of existing vehicles to propose alternatives to improve the crashworthiness of railway freight cars through collision acceleration analysis using a one-dimensional collision analysis method. A collision scenario of railway shunting and crash accidents was selected from the collision accident cases and international standards. A one-dimensional collision simulation using LS-DYNA was performed according to those scenarios. As a result, the acceleration level of the freight wagon was calculated to be under 2g and was predicted to meet the EN 12663 standard in the shunting situation. On the other hand, the result of crash simulation with an impact velocity between 10 and 15 km/h revealed the shock absorber capacity of the railway coupler to be insufficient in a crash situation, resulting in increased acceleration, and carbody deformation could be predicted. As a method of improving the crashworthiness, a deformation tube-type energy absorber was applied to the coupler system, and collision analysis was performed again with new energy absorption strategy. Overall, the simulation showed that the acceleration level was decreased by 12% of the conventional freight-car energy absorption system.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.5
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• pp.35-44
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• 2021

In recent times, several studies have been conducted focusing on crashes occurring on the main segment of the highway. However, there is a dearth of research dealing with traffic safety relating to other highway facilities, especially ramp areas. According to the Korea Expressway Corporation's Expressway Information Service, 6,717 crashes have occurred on ramps in the five years from 2015~2019, which accounts for about 15% of all highway accidents. In this study, the simple and full safety performance functions (SPFs) were evaluated and explored using different statistical distributions (i.e., Poisson Gamma (PG) and Poisson Inverse Gaussian (PIG)) and techniques (i.e., fixed effects (FE) and random effects (RE)) to provide more accurate crash prediction models for highway ramp sections. Data on the geometric characteristics of traffic and roadways were collected from various systems and with extensive efforts using a street-view application. The results showed that the PIG models present more accurate crash predictions in general. The results also indicated that the RE models performed better than FE models for simple and full SPFs. The findings from this study offer transportation practitioners using the Korea Expressway Corporation's Expressway a dependable reference to enhance and understand traffic safety in ramp areas based on accurate crash prediction models and empirical evidence.

• Journal of Korean Society of Transportation
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• v.34 no.6
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• pp.535-547
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• 2016

This study aims to identify factors that affect the degree of injury severity sustained in traffic crashes on work zone of Korean expressways. To this end, decision tree method was applied to identify influential factors on injury severity and compare characteristics of those factors between work zone and non-work zone. The results from the comparison show that the risk of severity was low when traffic volume and heavy vehicle ratio are high because the factors lower the overall section speed. On the other hand, when the traffic volume and the heavy vehicle ratio are low, the section speed increased and the tendency for high injury severity was confirmed. These findings are expected to help transportation planners and engineers understand which risk factors contribute more to severe injury in the work zones such that they can effectively prepare and implement safety countermeasures.

• International Journal of Highway Engineering
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• v.16 no.6
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• pp.149-158
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• 2014

PURPOSES : The bridge section of the expressway has a worse driving environment than the general section. However, traffic safety countermeasures are focused only on the bridge section. Traffic safety countermeasures on the section before entry to the bridge and the section after exit from the bridge are applied only when the bridge has a long-span section. Accordingly, this study will verify the necessity of extending the application of traffic safety countermeasures to areas that are affected by the bridge. METHODS : This study determines the areas that are affected by the bridge as well as the areas that are affected by locations with frequent traffic accidents and suggests the risk factors by affected areas through canonical discriminant analysis. For the analysis, traffic accident data for 3 years, which occurred on bridge sections in six major expressway lines, were used. RESULTS : The numbers of traffic accidents were 469 before the bridge, 281 on the bridge, and 468 after the bridge. The variables that have impact on the seriousness of accidents are as follows: speeding, excess manipulation of the steering wheel, and failure to secure safety distance for accidents that occurred before the bridge section; speeding, excess manipulation of the steering wheel, and dozing off for accidents that occurred on the bridge; and speeding and failure to secure safety distance for accidents that occurred after the bridge section. CONCLUSIONS : Areas affected by the bridge show higher accident rates than the bridge section; therefore, imposing traffic safety countermeasures on the integrated section of the bridge and the affected areas is required. It is believed that the results suggested in this study could be effectively used in the prevention of traffic accidents by imposing custom-made safety countermeasures for each section.