• Journal of Surface Science and Engineering
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• v.41 no.3
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• pp.121-128
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• 2008

High strength 7xxx aluminum alloys have been applied to automotive bump back beam of the some limited model for light weight vehicle. The aluminum bump back beam is manufactured through extrusion, bending and welding. The residual stress given on these processes combines with the corrosive atmosphere on the road spreaded with corrosive chemicals to melt snow to occur the stress corrosion cracking. The composition of commercial 7xxx aluminum has Zn/Mg ratio about 3 and Cu over 2 wt% for better strength and stress corrosion cracking resistivity. But this composition isn't adequate for appling to the automotive bump back beam with high resistance to extrusion and bad weldability. In this study the composition of 7xxx aluminum alloy was modified to high Zn/Mg ratio and low Cu content for better extrusion and weldability. To estimate the resistivity against stress corrosion cracking of this aluminum alloy by slow strain rate test, the corrosion atmosphere and strain rate separate the stress corrosion cracking from conventional corrosion must be investigated. Using 0.6 Mol NaCl solution on slow strain rate test the stress corrosion cracking induced fracture was not observed. By adding 0.3% $H_2O_2$ and 0.6M $Na_2SO_4$ to 1M NaCl solution, the corrosion potential and current density of polarization curve moved to active potential and larger current density, and on the slow strain rate test the fracture energy in solution was lower than that in pre-exposure. These mean the stress corrosion cracking induced fracture can be estimated in this 1M NaCl + 0.3% $H_2O_2$ + 0.6M $Na_2SO_4$ solution. When the strain rate was below $2{\times}10^{-6}$, the stress corrosion cracking induced fracture start to be observed.

• The Transactions of the Korea Information Processing Society
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• v.6 no.12
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• pp.3710-3717
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• 1999

For the development of unmanned autonomous vehicle, it is essential to detect obstacles, especially vehicles, in the forward direction of navigation. In order to reliably exclude regions that do not contain obstacles and save a considerable amount of computational effort, it is often necessary to confine computation only to ROI(region of interest)s. A ROI is usually chosen as the interior region of the lane. We propose a computationally simple and efficient method for the detection of lanes based on Hough transform and quadratic curve fitting. The proposed method first employs Hough transform to get approximate locations of lanes, and then applies quadratic curve fitting to the locations computed by Hough transform. We have experimented the proposed method on real outdoor road scene. Experimental results show that our method gives accurate detection of straight and curve lanes, and is computationally very efficient.

• International Journal of Highway Engineering
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• v.11 no.1
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• pp.69-83
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• 2009

According to the accident statistics of 2006, it can be recognized that drivers' characteristics and driving behaviors are the most causational factors on the traffic accidents. At present, many recording tools such as digital speedometer or black box are distributed in the market to meet social requests of decreasing traffic accidents and increasing safe driving behaviors. However, it is also true that the system preventing any possible vehicle accidents in advance has not been developed. In this study, we developed critical value for deciding dangerous driving behaviors. The developed critical value could be used to contribute to safety driving management systematization and safety driving behaviors.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.21-32
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• 2007

The linear traffic model(Vertical queueing model) that is adopted widely in traffic flow estimation assumes that all vehicles have the identical motion before joining a queue at the stop-line. Thus, a queue is supposed to form vertically not horizontally. Due to the simplicity of this model, the departure time of the leading vehicle is assumed to coincide with the start of effective green time. Thus, the delay estimates given by the Vertical queueing model is not always realistic. This paper explores a microscopic traffic model(a Kinematic Car-following model at Signalised intersections: a KCS traffic model) based on the one dimensional Kinematic equations in physics. A comparative evaluation in delay and sensitivity of delay difference between the KCS traffic model and the previously known Vertical queueing model is presented. The results show that the delay estimate in the Vertical queueing model is always greater than or equal to the KCS traffic model; however, the sensitivity of delay in the KCS traffic model is greater than the Vertical queueing model.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.65-74
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• 2007

There have been research and studies on rumble strip effectiveness in terms of accident reduction since rumble strips were first installed in 1950's. Research has shown that rumble strips reduce accidents from drowsy and inattentive driving. The present research statistically analyze the accident reduction effect of rumble strips based on accident reports obtained from rumble strip installed 377 places of nation wide freeway lines. Based on the results, rumble strips are effective in reducing accident frequencies 32.3%. The probable various factors inducing accidents are identified. These include drowsiness, speeding, inattentiveness, vehicle defectiveness, and short headways. It was found that rumble strips are effective in reducing A, B, C leveled accidents, and in reducing clear, cloudy, and rainy weather accidents. The results may make clear and expand probable types of accidents that rumble strips would reduce, then reduce the total accidents on freeway lines.

• International Journal of Highway Engineering
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• v.15 no.5
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• pp.91-99
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• 2013

PURPOSES : This study aims at proposing the methodology for benefit evaluations in pavement maintenance methods and timings using KoPMS(Korean Pavement Management System) software which was developed for efficient pavement management. METHODS : This study classified pavement sections into 4 clusters considering AADT(Annual Average Daily Traffic) and ESAL(Equivalent Single-Axle Load) using cluster analysis and used the deterioration models in each cluster. Increased user costs due to pavement deterioration as time goes by and agent costs for maintenance were estimated. Based on deterioration model and KoPMS software, Methodology for benefit evaluation was proposed in pavement maintenance methods and with/without implementation using real pavement section data. RESULTS : This study verified that considering agent costs only would be constrained to decide pavement maintenance methods and timings, and ascertained that decision making with agent and user costs would be effective. In addition, this study revealed that pavement maintenance methods and timings can be affected by AADT and ESAL and frequent pavement maintenances can be more efficient for benefits in pavement sections with more AADT and ESAL. Also this study found that user costs would be more affected to decision making than agent costs. Moreover, Delay of conducting pavement maintenance caused increased vehicle operating costs and environmental costs because of poor conditions of pavements. CONCLUSIONS : This study proposed LCCA and benefit estimation methodology of pavement with considering agent and user costs. The results of this study can be used for baseline data of efficient pavement asset management.

• International Journal of Highway Engineering
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• v.15 no.5
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• pp.47-55
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• 2013

PURPOSES : The purpose of this study is to investigate the optimal joint positions which can minimize distresses of concrete pavement containing box culvert with horizontally skewed angles. METHODS : The concrete pavement containing the box culvert with different skewed angles and soil cover depths was modeled by 3 dimensional finite element method. The contact boundary condition was used between concrete and soil structures in addition to the nonlinear material property of soil in the finite element model. A dynamic analysis was performed by applying the self weight of pavement, negative temperature gradient of slab, and moving vehicle load simultaneously. RESULTS : In case of zero skewed angle ($0^{\circ}$), the maximum tensile stress of slab was the lowest when the joint was positioned directly over side of box culvert. In case there was a skewed angle, the maximum tensile stress of slab was the lowest when the joint passed the intersection between side of the box culvert and longitudinal centerline of slab. The magnitude of the maximum tensile stress converged to a constant value regardless the joint position from 3m of soil cover depth at all of the horizontally skewed angles. CONCLUSIONS : More reasonable and accurate design of the concrete pavement containing the box culvert can be possible based on the research results.

• Journal of Korean Society of Transportation
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• v.24 no.5 s.91
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• pp.123-133
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• 2006

Seoul and many large cities in Korea have implemented Median Exclusive Bus Lane(MEB). But exclusive bus lane in the middle of the road caused new contradictions between left turn movement and through bus movement and several signal operation techniques like 'left turn Protected' and 'overlap phase' couldn't be applied in intersections on MEB. We suggest 'Bus-only Signal for median lane technique as solution of these problems This study presents optimum signal time design process and detailed algorithms for intersections where bus-only signals are installed. As a test field. we took Yang-Je intersection where Median Exclusive Bus Lane go through. and have large gap in volume of left turn in main direction. And we verified that revised optimum signal time including overlap phase can reduce average delay time of vehicle through before and after simulation.

• Journal of Korean Society of Transportation
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• v.28 no.2
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• pp.45-52
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• 2010

The objective of this paper is to develop and apply a method that estimates the amount of traffic congestion (vehicle hours of delay) caused by traffic accidents that occur on freeways in Korea. A key feature of this research is the development of a method to separate the non- recurrent delay from any recurrent delay that is present on the road at the time and place of a reported accident. The main idea to separate these two delays is to use the speed difference between speed under accident condition and speed under normal flow condition. For the case study application, two datasets were combined to accomplish the objective of the study: (1) accident data and (2) traffic flow data. Eventually, the results can be useful for the performance evaluation of accident reduction program, for strategic plans to cope with congestion caused by traffic accidents, and for rectification of the estimation method for traffic congestion costs.

• Journal of Korean Society of Transportation
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• v.31 no.5
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• pp.26-36
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• 2013

Highway traffic safety evaluation of area on the basis of the accident rate has a limitation, thus its result is dependent on the exposure variables. It works an obstacle to decision making for effective budget execution. In this paper, we developed a methodology of taking simultaneously macroscopic exposure indicators into account in evaluating the safety using least squares method. The weight of exposure indicators to make up of highway traffic safety evaluation index is that accident rate per population, accident rate per registration vehicle and accident rate per length of road is 0.29, 0.52 and 0.19 respectively and calculated the highway traffic safety index of total local governments in Korea. The methodology to calculate highway traffic safety evaluation index proposed in this paper can be utilized in executing the traffic safety policies to increase the efficiency of investment about traffic safety budget.