• 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.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.5
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• pp.75-82
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• 2021

The number of traffic accidents is about 230,000, and due to non-recurring congestion and high driving speed, the number of deaths per traffic accident on freeways is more than twice compared to other roads. Currently, traffic information is provided based on nodes and links using the centerline of the road, but it does not provide detailed speed information. Recently, installing sensors for vehicles to monitor obstacles and measure location is becoming common not only for autonomous vehicles but also for ordinary vehicles as well. The analysis using large-capacity location-based data from such sensors enables real time service according to processing speed. This study presents an mapping method for individual vehicle data analysis based on space. The processing speed of large-capacity data was increased by using method which applied a quaternary notation basis partition method that splits into two directions of longitude and latitude respectively. As the space partition was processed, the average speed was similar, but the speed standard deviation gradually decreased, and decrease range became smaller after 9th partition.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.2
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• pp.116-127
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• 2017

A fog on road is known as a weather factor that affects traffic flow. The method in order to solve the problem, recently, Variable Speed Limit(VSL) which provide reasonable speed limit by road and weather conditions in real time is introduced. However, if drivers do not comply with VSL, the road safety more decrease than without VSL because individual vehicle's speed deviation is larger than without VSL. Therefore, this paper aims to analyze to speed limit compliance and traffic characteristics under foggy conditions with and without VSL. A test using driving simulator divides into normal and foggy condition with visibilities are 200m, 150, 50~100m. The test results showed that 70 subjects's average speed mostly obeyed speed limit, but speed deviation generally declined with VSL. Especially, the speed deviation more reduced under foggy conditions. According to this study, compliance of VSL clearly rose in low visibility and VSL helped improve road safety due to reduction of speed deviation. The results of this study are expected to make use of reasonable speed limit for reference.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.1
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• pp.16-26
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• 2011

Variable speed limit(VSL) is one of the highway ITS techniques designed to prevent accidents and traffic slow down by reducing congestion or speed variation between vehicles and lanes prior to arrive at the accident location by limiting speed. In Korea, while people have recognized the need for variable speed limit beginning with Seoul's urban expressway and installed facilities in order to provide guide for speed limit per lane and lane use, there has not been enough development of algorithm for internal administration as well as research on the basic principles behind administering variable speed limit. This study is for modeling and evaluating the VSL strategies based on the traffic flow theory. Supply-Demand method of the Cell Transmission Model is applied to demonstrate the traffic features and shockwaves to upstream of the bottleneck with/without VSL. We verified the explanation of Cell Transmission Model for the numerical example. and as the result, it is found that VSL strategies can reduce the total travel time in the congested section and variation of the speed. It means VSL is useful to improve the traffic condition and the safety on highway

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.6
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• pp.54-66
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• 2018

In this study, vehicle speeds at acceleration and deceleration lanes of rest areas for drowsy drivers were investigated to analyze effects of acceleration and deceleration lane lengths, grades and curve radius. In addition, we used VISSM to analyze proper lengths of rest area's acceleration and deceleration lanes. Several VISSIM scenarios with different lengths of acceleration and deceleration lane were constructed. Through VISSIM simulation, we collected individual vehicle speed data to analyze speed changes by different lengths of acceleration and deceleration lanes. As a result of the vehicle speed change investigation, grades and curve radii of the rest area affected the speed, most of all lengths of acceleration and deceleration lane showed a great effect on the vehicle speed. In the case of short lengths of acceleration and deceleration lane, speed variation among vehicles was significant. If the deceleration lane length is short, the vehicle enters a state in which the speed is not sufficiently reduced, and if the acceleration lane length is short, the vehicle enters a state in which the speed is not sufficiently accelerated showing high risks of conflicts and accidents. It is recommended that 245m length of deceleration lane and 370m length of acceleration lane should be installed at least to secure safety and manage conflicts relevantly.

• Journal of Korean Society of Transportation
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• v.23 no.4 s.82
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• pp.17-28
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• 2005

About 91.1% of Railway-Highway Crossings (RHC) in Korea use a Constant Distance Warning System(CDWS), while about 8.9% use a Constant Warning Time System(CWTS). The CDWS does not recognize speed differences of approaching trains and provides only waiting times to vehicles and pedestrians based on the highest speed of approaching trains. Under the CDWS, therefore, low speed trains provide unnecessary waiting times at crossings which often generates complains to vehicle drivers and pedestrians and may cause wrong decisions to pass the crossings. The objective of this research is to improve the safety of the RHC by developing accurate a CWTS. In this research a train speed and location detection system was developed with ultra sonic detectors. Locations of the detectors was decided based on the highest speed and the minimum warning time of Saemaul of 160 km/h. To validate the algorithms of the newly developed systems the lab tests were conducted. The results show that the train detection system provides accurate locations of trains and the maximum error between real speeds of trains and those of the system was 0.07m/s.

• Information and Communications Magazine
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• v.25 no.7
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• pp.10-15
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• 2008

최근 고속도로의 길이와 운전 차량 수가 빠른 속도로 증가하고 있어 운전자들에게 고속도로 교통상황를 신속하고 정확하게 제공하는 것이 중요한 문제로 대두되고 있다. 고속도로통행료수납시스템(TCS: Toll Collection Systrem)은 전국 고속도로를 주행하는 차량의 통행 정보를 실시간으로 제공하므로 교통 상황 예측에 유용하게 활용될 수 있다. TCS 자료는 차량이 입구영업소를 통과한 후 출구영업소를 통과하는 데 소요된 시간으로서, 운전한 시간, 휴게소 체류시간 등을 모두 포함한 통행시간으로 운전자의 운전 특성, 통행 목적, 피로의 정도에 따라 편차가 크게 나타난다. TCS 자료의 통행시간을 기초로 예측된 정보는 이러한 불확실성을 포함하고 있기 때문에 이를 활용하기 다양한 데이터처리 기법이 필요하다. 본 논문에서는 TCS 자료의 효율적인 전처리 및 교통 예측 기법 현황에 대하여 기술하고 향후 발전 방향을 제시하였다.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2008.06a
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• pp.195-201
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• 2008

본 연구에서는 고속도로와 같은 연속류 에서의 통행시간 군집화 현상을 연구하여 신뢰성 있는 단위 시간 당 구간 대표 통행시간을 구하는 전처리 방법을 제시하는데 목적이 있다. 현재까지는 단위시간 당 구간의 통행시간 대푯값으로 하나의 평균값(Mean), 최빈값(Mode), 또는 중앙값(Median)이 사용되었다. 이의 문제점은 운전자의 주행 습관(빠른 주행, 느린 주행), 휴게소 이용, 도로 정체 등 다양한 요인으로 인하여 차량일 구간 주행 속도 간 편차가 많아 현재 사용하는 1개의 대푯값으로는 전체 차량의 운행 특징을 정확히 표현하기가 곤란하다는 점이다. 이를 개선하기 위하여 본 연구에서는 군집 방법을 이용하여 차량군을 복수의 비슷한 군집으로 나누고 나누어진 그룹별로 통행시간 대푯값을 선정하는 방법을 제시하고 실험하여 이 방법이 효과적임을 증명하였다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.2
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• pp.62-73
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• 2020

Access management is aimed at preserving the road's high intercity mobility. In urbanized areas, immoderate acceleration lane-length requirements restrict the accessibility of land. Therefore, there are many opinions to revise the minimum acceleration lane-length requirement. For this purpose, it is important to diagnose the effects of slow vehicles on the mainline. This study analyzed a single merging vehicle's total delay occurrence depending on the mainline traffic flow rate and merging speed. A linear relationship was observed between the mainline traffic flow rate and total delay. As a merging speed increases gradually from 40km/h to 100km/h in 20km/h intervals, the total delay decreases by 5.0, 1.6, and 5.1 times, respectively. This shows that the ideal condition with the total delay is less than 0.5 vehicle·sec when there is no speed difference between the mainline and merging vehicle. On the other hand, given the one-second response time of drivers, the total delay occurrence was slightly low when the speed difference between the mainline and merging vehicle was less than 20km/h.

• Journal of the Korean Society for Railway
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• v.17 no.3
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• pp.157-164
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• 2014

The contact force between the pantograph and the catenary is a key factor determining the current collection quality, as they can ensure stable electrical power to the train. In this study, we analyzed the dynamic contact force for HEMU-430X depending on the train speed. It was confirmed through the results that the standard deviation of the contact force increases with an increase in the train speed. It was also verified that the span of the catenary system is a very important factor with regard to the contact force when analyzed with frequency analysis. To secure stable power in speed that exceeds 400km/h, the statistical variation of the contact force should be minimized. To realize this, the catenary tension was increased and the mass of the pan-head was decreased. The ensuing effects were then quantitatively analyzed in terms of the contact force. In addition, the differences in the contact force between a tunnel and an open field were analyzed based on a frequency analysis.