• Proceedings of the KOR-KST Conference
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• 2007.05a
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• pp.198-207
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• 2007

• Journal of Korean Society of Transportation
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• v.25 no.4
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• pp.7-19
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• 2007

The purpose of posted speeds is to provide a speed that ensures the safety of vehicle flow according to given road situations. Because of this, posted speeds must be carefully examined, and posted speeds at freeway exits and entrances in particular should consider car characteristics. Posted speeds at freeway exits and entrances must take changing speeds due to curve radiuses into consideration and in this study, an 85th percentile speed becomes the most important element to consider. When it is considered that most traffic accidents occur because of variations in speed between cars, posted speeds should be set after considering car traveling characteristics. Within these dimensions, instead of putting significance on an upper direction regulation or lower direction regulation, speed distributions which fit to the characteristics of each road should be fully considered. Accordingly, this study evaluated appropriate posted speeds that will reduce the dangers of traffic accidents through posted speed regulations of roads now in operation by offering a posted speed setting method theory, using entries at Yangji, Yongin, and Cheongwon interchanges as subjects.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.6
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• pp.162-172
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• 2009

Improvement of roadway environments to accommodate elderly drivers' declining driving capabilities are required. Currently, even the types of roadway designs vulnerable to elderly drivers have not been revealed in Korea. Thus, this study aims to analyze the types and vulnerabilities of the roadway designs that elderly drivers experience more accidents based on crash data of the Korean National Police Agency. This study has also reviewed foreign guidelines enhancing their safety on different roadway designs. Compared with normal drivers, elderly drivers tend to be more frequently involved in traffic accidents on intersections and vehicle-to-vehicle accidents on curved roadway segments. Assuming freeway interchanges are also risky sections, this study has also examined several methods to reduce elderly driver-related accidents on freeway ramp areas.

• Journal of Korean Society of Transportation
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• v.23 no.2
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• pp.95-106
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• 2005

Road accidents are considered as the result of a complex interplay between road, vehicle, environments, and human factors. Little study, however, has been carried out on the attributes of human factor compared to the road geometric conditions and traffic conditions. The previous researches focused on mainly both traffic and geometric conditions on specific location. Therefore, it's hard to explain phenomenon of the high traffic accident rates where road and traffic conditions are good. Because of these reasons, accident analysis has contributed on geometric improvement and has not contributed on traffic management such as selection of attention section, driver napping alert, etc. The freeway incident management is also associated with reliable prediction of incident occurrences on freeway sections. This paper presents a method for estimating the effect of trip length on freeway accident rate. A PAR (Potential Accident Ratio), the new concept of accident analysis, considering TLFDs (Trip Length Frequency Distributions) is suggested in this paper. This approach can help to strengthen freeway management and to reduce the likelihood of accidents.

• Journal of Korean Society of Transportation
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• v.17 no.2
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• pp.21-27
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• 1999

The objective of this study is to clarify the relationship between accident rate and V/C for freeway facility. The relationship can be used as a basic reference to predict and prevent traffic accident. The traffic volume and the number of accidents from 1992 to 1997 on Shingal-Ansan Freeway were analyzed in this study to clarify the relationship. Hourly accident rate and V/C were calculated for each facility sections : basic freeway section, tunnel section and toll gate section. The accident rate models consisting of an independent variable of V/C were established by repression analysis and compared with each other. The relationship between accident rates and V/C ratios represented U-shaped pattern for all sections. The result of this study indicates that accident rates are highest in the low hourly V/C range, decrease with increasing V/C ratio, and then increase as the V/C ratio increases. The accident rate of toll gate section is in general higher than that of other sections. Although the accident rate of tunnel section is higher than that of basic freeway section when V/C is above 0.67, there is no significant difference of accident rate between basic freeway and tunnel section when V/C is between 0.5 and 0.8. Basic freeway tunnel and toll gate section have the minimum accident rate when V/C is 0.78, 0.75 and 0.57 respectively.

• 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.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.6
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• pp.47-54
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• 2021

The number of freeway traffic accidents in Korea is about 4,000 as of 2020, and deaths per traffic accident is about 3.7 times higher than other roads due to non-recurring congestion and high driving speed. Most of the accident types on freeways are side and rear-end collisions, and one of the main factors is hazard traffic flow caused by merge, diverge and accidents. Therefore, the hazard traffic flow, which appears in a continuous flow such as a freeway, can be said to be important information for the driver to prevent accidents. This study tried to classify hazard traffic flows, such as the speed change point and the section where the speed difference by lane, using individual vehicle information. The homogeneous segment of speed was classified using spatial separation based on geohash and space mean speed that can indicate the speed difference of individual vehicles within the same section and the speed deviation between vehicles. As a result, I could extract the diverging influence segment and the hazard traffic flow segment that can provide dangerous segments information of freeways.

• Journal of Korean Society of Transportation
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• v.29 no.4
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• pp.103-111
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• 2011

The speed is one of the significant factors affecting accident occurrence. In particular, freeway accidents are highly associated with the speed because vehicles travel on the freeway at higher speed leading to greater potential of severer injury. Efforts attempting to relating speed with accident occurrence have not been significantly made in Korea. The objective of this study is to model the relationship between speed and accident rate on freeways. Loop detector data and accident data obtained from a stretch of Kyungboo freeway during the recent five years, 2005-2009, were used to establish the model. Multiple linear regression analyses showed that median, minimum and standard deviation of speed were contributing variables in the model. The statistical significance identified by the analyses supports the feasibility of the model in evaluating various transportation policies and operations strategies in terms of traffic safety.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.3
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• pp.73-84
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• 2010

This study presents a novel method to identify hazardous segments of freeway using global positioning system(GPS) based probe vehicle data. A variety of candidate contributing factors leading to higher potential of accident occurrence were extracted from the probe vehicle dataset. The research problem was defined as a classification problem, then a well-known classifier, bayesian neural network was adopted to solve the problem. A binary logistic regression technique was also used for selecting salient input variables. Test results showed that the proposed method is promising in extracting hazardous freeway sections. The outcome of this study will be effectively used for evaluating the safety of freeway sections and deriving countermeasures to prevent accidents.

• Journal of Korean Society of Transportation
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• v.25 no.1 s.94
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• pp.23-35
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• 2007

Freeway diverging areas are very vulnerable to traffic accidents due to abrupt vehicle speed changes and geometric changes. Therefore, in designing diverging areas, much attention should be Paid to safety The Present design criteria about freeway diverging areas regulate transition sections for lane changes, deceleration lanes, transition corves for direction changes. and other similar items. However, the design criteria were often violated in implementation because of ambiguities in the criteria. This study aims at clarifying and improving the present design criteria for freeway diverging areas. For this, field survey data and traffic accident data for diverging areas were analyzed.