• KIISE Transactions on Computing Practices
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• v.22 no.9
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• pp.405-418
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• 2016

Recently, many researchers have studied the VSL decision method using traffic information in multiple detector zones. However, this method selects incorrect VSL starting points, leading to the selection of the wrong speed control zone and calculation of the wrong VSL, causing traffic congestion. Eventually, the Unstable VSL system causes more congestion on the freeway. This paper proposes an improved VSL algorithm stably operated in multiple detector zones on the Korea highway. The proposed algorithm selects a preliminary VSL start station (VSS) expected to end the congestion using the acceleration of stations. It also determines the VSS at each congestion area. Finally, it calculates the VSL relative to the determined VSS and controls the vehicles that enters the traffic congestion zone. The developed strategy is compared with Real-time Variable Speed Limits for Urban Freeway (RVSL) to test the stability and efficiency of the proposed algorithm. The results show that the proposed algorithm resolves the problems of the existing algorithm, demonstrated by the correct VSS decision and the reduction of total travel time by 1-2 minutes.

• International Journal of Highway Engineering
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• v.14 no.2
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• pp.117-129
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• 2012

Road safety audit is the preventive enhancement strategy for safety. : it gets rid of beforehand the potential factor of a traffic accident in the stage of road planning and design and it evaluates the appropriation for road geometric structure or safety facility to prevent traffic accident in the stage of operation after the construction. Since this strategy is introduced to our country in the early 2000s, various projects have been processed and it was legislated recently. And now, the evaluation of past project for its continuation is needed. Therefore, in this study the evaluation of road safety audit on existing freeway is performed. The spatial extent of this study is Yong-dong line on which the safety treatment was executed in 2005 and 2006. And, the temporal range of this study is each 2-year of before and after from 2005 and 2006. The empirical bayes method of observational evaluation studies is applied to analyze. As a result, there is an effect of improvement on most of treated sections. But there is ineffective or negligible on some sections. Compared with the detail of treatment on each section, the effect of multiple or various treatments is good for that section. On the other hand, the section on which effect doesn't appear is the result of single or unimportant treatments. Throughout these results, the concrete analysis can be performed and the countermeasures designed for the section on which effect doesn't appear. Also it is used as reference to the future plan and direction of road safety audit on existing freeway.

• Journal of Korean Society of Transportation
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• v.24 no.3 s.89
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• pp.29-37
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• 2006

As a recurrent congestion of urban freeway occurs in almost same time and section, it is possible to manage the congestion effectively by the expectation and advance correspondence. In the existing traffic management system. we have used pattern data to manage a recurrent congestion. But it is not applicable to an urban freeway which kas various traffic circumstance. In this study, the probability by travel speed using a statistical distribution method will be used to predict the probability of recurrent congestion. It is expected that we can get the point of time and the duration of recurrent congestion, and we can devise an effective advance correspondence and a transportation operation.

• Journal of Korean Society of Transportation
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• v.28 no.2
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• pp.151-159
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• 2010

This paper presents a research result that was performed to develop a more accurate freeway crash prediction model than existing models. While the existing crash models only focus on developing crash relationships associated with highway geometric conditions found on a short section of a crash site, this research applies a different approach considering the upstream highway geometric conditions as well. Theoretically, crashes occur while motorists are in motion, and particularly at freeways vehicle speed at one specific point is very sensitive to upstream geometric conditions. Therefore, this is a reasonable approach. To form the analysis data base, this research gathers the geometric conditions of the West Seaside Freeway 269.3 km and six years crash data ranging 2003-2008 for these freeway sections. As a result, it is found that crashes fit well into Negative Binomial Distribution, and, based on the developed model, total number of crashes is inversely proportional to highway curve length and radius. Contrarily, crash occurrences are proportional to tangent length. This result is different from existing crash study results, and it seems to be resulted from this research assumption that a crash is influenced greatly by upstream geometric conditions. Also, this research provides the expected effects on crash occurrences of the length of downgrade sections, speed camera placements, and the on- and off- ramp presences. It is expected that this research result is useful for doing more reasonable highway designs and safety audit analysis, and applying the same research approach to national roads and other major roads in urban areas is recommended.

• Journal of Korean Society of Transportation
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• v.24 no.4 s.90
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• pp.129-148
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• 2006

The objective of this thesis is to develop a capacity analysis and to develop a methodology to evaluate Level of Service over the entire freeway sections by single MOE (Measure of Effectiveness) This study set forth from a following viewpoint. to analyze entire freeway sections as freeway facility system, it is important to identify the exact point where congestion would occur and the extent of the congestion. Therefore, in this thesis, congestion mechanism on freeways was figured out and congestion analysis methodology was developed. Thereby maximum possible throughput rate and maximum throughput rate in bottleneck sections were calculated and a congestion analysis was carried out. The difference between the new method and existing Procedures is that maximum possible throughput rate and maximum throughput rate. that can be considered as capacities of un-congested and congested flow in the bottleneck section, are variable capacities dependent on demand flow.

• Journal of Korean Port Research
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• v.5 no.1
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• pp.29-54
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• 1991

In this study, to identify the ineffectiveness of inter-connected system of cargo volume between the Pusan Port and inland areas and also to make more rational suggestions, the following conclusions were drawn by analyzing Container Cargo Traffic from BCTOC to Off-Dock CY: 1. There existed about 30% to 50% reduction in the container transport times when the container transport vehicles were operated during the off-peak period to alleviate the traffic congestion due to mixed traffic. 2. There appeared to be more economic when Off-Dock DY's scattered around the City of Pusan were unified in one ODCY Unit at YangSan, and the Exclusive Overpass Freeway System for the container transport vehicles were constructed and operated on the existing Urban Freeway from BCTOC ti this ODCY Unit (Expected to make about 230 billions Won in net present value by NPV method).

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.5
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• pp.38-47
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• 2009

This paper aims to evaluate the freeway traffic management Strategy based on exTMS according to traffic situation of freeway. As freeway user's demands increase, we thus need future-oriented and optimized traffic management. So, through improving the existing system and introducing the advanced system, these systems evaluate for not only preparing the application in real world but also preliminary feasibility. To evaluate effects of the traffic management based on exTMS, in this study, shoulder LCS, advanced VMS(assumption in it is improving next-generation system which it can be offering diverse dynamic traffic information), Ramp-metering system are applicated in simulation. In addition, this study evaluates the effect when all proposed systems are applicated, and compare the individual effect of when independent system is applicated, through considering about traffic condition of V/C=0.5, V/C=0.8, V/C=1.2. The study results show that all assumed cases, the travel speed were improved according to the increasing V/C. Furthermore, the results of evaluated the individual system show that the shoulder LCS was found to be the largest effect, and the effect of VMS(detour rate is 11%) is larger than the other cases.

• Journal of Korean Society of Transportation
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• v.31 no.4
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• pp.85-94
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• 2013

The Continuous Risk Profile (CRP) has been well known to be the most accurate and efficient among existing network screening methods. However, the classical CRP uses safety performance functions (SPFs) which require a huge investment to construct a database system. This study aims to suggest a new CRP method using average crash frequencies of homogeneous groups, instead of SPFs, as rescaling factors. Hierarchical clustering analysis is performed to classify freeway segments into homogeneous groups based on the data of AADT and number of lanes. Using the data from I-880 in California, the proposed method is compared to other several network screening methods. The results show that the proposed method decrease false positive rates while it does not produce any false negatives. The method developed in this study can be easily applied to screen freeway networks without any additional complex database systems, and contribute to the improvement of freeway safety management systems.

• International Journal of Highway Engineering
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• v.17 no.5
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• pp.123-133
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• 2015

PURPOSES : This study aimed to develop a new highway capacity estimation method and provide comparative results among traditional capacity estimation methods and the recommended values in the latest version of KHCM. METHODS : The limitations of the existing methods, such as inconsistency and underestimation of the capacity value, are summarized through an extensive literature review. To overcome these limitations, a new method is introduced by adopting a definition of capacity and traffic flow characteristics at or near breakdown points. This method can produce the capacity value by searching a point corresponding to the maximum traffic flow through analysis of gradient changes (point of inflection) of the traffic flow and speed distribution. Comparative results of capacity values from each method are also presented to validate the new method by using data collected from detectors on freeways. RESULTS: From the analysis results, it is shown that a consistent capacity value can be estimated by applying the new method. In addition, the resulting capacity values are 3%-4% higher than those recommended in KHCM. CONCLUSIONS : The capacity values listed in the current KHCM tend to produce underestimated results. The new method presented in this paper may be included in the future edition of KHCM.

• International Journal of Highway Engineering
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• v.16 no.1
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• pp.57-62
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• 2014

PURPOSES : Capacity is a main factor of determining the number of lane in highway design or the level of service in road on operation. Previous studies showed that breakdown may occur before capacity is reached, and then it was concluded that capacity is a stochastic value rather than a deterministic one. In general, estimating capacity is based on average over maximum traffic volume observed for capacity state. This method includes the empirical distribution method(EDM) and would underestimate capacity. This study estimated existing empirical methods of estimating stochastic highway capacity. Among the studied methods are the product limit method(PLM) and the selected method(SM). METHODS : Speed and volume data were collected at three freeway bottleneck sites in Cheonan-Nonsan and West Sea Freeway. The data were grouped into a free-flow state or capacity state with speeds observed in the bottlenecks and the upstream. The data were applied to the empirical methods. RESULTS : The results show that the PLM and SM estimated capacity higher than EDM. The reason is that while the EDM is based on capacity observations only, the PLM and SM are based on free-flow high volumes and capacity observations. CONCLUSIONS : The PLM and SM using both free-flow and capacity observations would be improved to enhance the reliability of the capacity estimation.