• Journal of Korean Society of Transportation
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• v.31 no.3
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• pp.33-44
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• 2013

Personal Rapid Transit(PRT) has emerged as a promising transportation mode for transit-oriented sustainable communities. In this study, an alternative design of questionnaire survey is proposed in order to capture traveler's perception of an unexperienced transportation mode. This study aims at predicting the mode choice diversion behavior of potential PRT users who do not have experience of using it previously, considering their willingness-to-pay. The proposed model was applied to predict an aggregate forecast of PRT patronage for the city of Songdo where PRT is considered to be constructed. For validation of the proposed model, the price elasticity of PRT demand was analyzed, compared with existing models. The analysis results suggest that the proposed design of questionnaire survey is able to capture respondents' attitude and perception to unexperienced transportation mode in an effective manner. Also, they show that the proposed diversion rate model is more realistic than existing models in explaining the effects of users' willingness-to-pay for predicting PRT patronage.

• Journal of Korean Society of Transportation
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• v.28 no.4
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• pp.97-106
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• 2010

Environmental issues resulting from climate change and energy crises have become global issues, and cycling has gained greater popularity for sustainable transportation. Though many cities are trying to build bicycle roads, it is not easy to implement bicycle roads because there is little available space for bicycle facilities. Therefore, road diets have become more popular in Korea. However, there has been no intensive research to date of their impacts. The purpose of this research is to evaluate the effects of road diets and construction of bike lanes. Every benefit, including energy benefit, environmental benefit, and health benefit is considered, while only time savings benefit has been considered in previous studies. The benefit analysis for the Seoul metropolitan area as a case study shows that road diets have a (1) time saving benefit for only five percent of the mode share and (2) enough total benefit even if bicycle mode share is less than two percent.

• Journal of Korean Society of Transportation
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• v.17 no.5
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• pp.87-98
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• 1999

전통적인 교통계획 과정에서 이용되어 온 수요모형들은 대부분 수단선택과 통행배정을 나누어 실시하는 모형이 주를 이루어 왔다. 그러나 교통수단이 다양해짐에 따라 실제 통행자들은 통행 도중 환승을 통해 수단을 전환하는 경우가 발생하게 되며 이 경우 수단선택 과정과 통행배정 과정을 하나로 통합하여 분석할 필요가 있다. 따라서 기종점간 수단 분담율은 기점과 종점에서의 그 값이 다르지만 수단선택과 통행배정이 분리되어 있는 기존 모형을 적용할 경우, 출발과 도착시의 수단 분담율이 동일하게 나타나는 비현실적인 결과를 도출하게 된다. 이러한 문제는 통행수단을 통행의 기본단위로 보고, 수단통행량을 추정하기 때문에 그 수단을 이용하는 통행자들의 행태 대신 수단의 특성만이 모형화되기 때문이다. 따라서 기존의 교통계획 과정에서는 수단분담 과정과 통행배정과정이 분리됨에 따라 수단간 환승이 고려되지 않아 통행자들의 경로 구성과정을 정확히 표현하는데 어려움이 있었다. 또, 수단분담 모형으로 가장 많이 이용되는 로짓 모형의 경우 환승을 고려하면 비관련 대안간 독립성문제(CIA)가 발생하고, 환승경로 수요추정이 불가능해 사실상 통합 교통망과 같이 복수 수단이 운행하는 교통망은 분석하기 어렵게 된다. 본 연구에서는 이를 해결하기 위하여 사람통행(Person Trip)을 기반으로 하는 수단분담-통행배정 통합모형을 개발하고 기존의 결합모형과 그 결과를 비교하였다.

• Journal of the Korean Regional Science Association
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• v.32 no.4
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• pp.39-49
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• 2016

The main objective of this paper is to analyze university students' modal shift for commuting trip due to the introduction of new urban rail transit in a satellite city of metropolitan area. The paper uses SP(2011)/RP(2013) data collected from Yeungnam University in Gyeongsan City, which is a satellite city of Deagu Metropolitan City. So far few researches, especially using before-and-after individual SP/RP travel survey, have been conducted on analyzing university students' modal shift due to the introduction of new urban rail transit. For this research, some descriptive statistical analyses were conducted. Furthermore, some empirical logit models were estimated for analyzing factors affecting the modal shift. Finally, some important findings and policy implications are discussed. The significant findings from this research are summarized as follows. From the descriptive statistical analyses of SP and RP data, it is found that the rate of modal shift to rail transit is relatively high especially for bus travellers. Furthermore, from the empirical SP model estimation, it is found that time saving is the most important factor affecting the modal shift to urban rail transit. On the other hand, from the empirical RP model estimation, it is found that residential location is the most important factor affecting the modal shift to urban rail transit.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.389-389
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• 2022

상수도 관망에서의 유량 측정은 유수율을 결정하는 데 있어서 중요한 평가 수단이다. 따라서, 유량 측정을 위해 유량계를 활용하는데, 높은 빈도의 자료를 획득할 수 있는 수압계는 시중에서 저가로 활용 가능하지만, 상수도관망 예산의 상당부분을 차지하고 있는 유량계는 수압계보다 고가에도 낮은 빈도의 자료만을 획득하는 비용 대비 낮은 효율을 가진다. 만약 수압계의 측정자료를 유량자료로 고속전환하는 기술을 개발하면 기존의 유량계보다 적은 비용으로 고빈도의 유량자료를 획득할 수 있다. 상수도 관망에서 수압자료를 유량 자료로 전환하는 기술은 기존 관망에서 유도된 지배방정식에서 임의 관망에서 일련의 유도과정을 거쳐 상하류 단사이 수압과 유량의 관계를 형성하고, 이러한 관계를 활용하여 간단한 저수조-관망-밸브 체제에서 관망 내의 특정지점에서의 시간상 수압자료와 시간상 유량자료의 비를 정의한 다음, 임의의 지점에서 측정된 수압자료를 정의한 비로 나타나는 임피던스 역수를 역푸리에 전환하면 시간상의 유량자료를 획득할 수 있는 원리이다. 이러한 수압-유량 전환기술의 원리를 가지고 개발된 기술의 정확도를 확인하는 과정을 수행하였으며, 이는 전통적 천이류 해석 방법인 특성선 모델로 비교하는 수치해석적인 방법 그리고 실제 설치된 관망을 사용해서 수압을 측정하고, 지정된 지점에서 유량을 정밀측정하여 비교하는 실험적인 방법을 통해 정확도를 비교해봄으로써 개발된 기술을 검증해보고자 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2D
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• pp.193-201
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• 2011

The provision of traffic information plays an important role in increasing social benefit not only by saving travel time for individuals but also by improving the efficiency of road operation. VMS(Variable Message Sign) helps on-wheel drivers easily understand the road situation, and also provides real-time traffic information to people on the streets. However, it has not been sufficiently studied on how traffic information based on VMS influences on the drivers' selection of route. This study investigated how drivers use VMS traffic information and how they are satisfied with it. Then, the model of drivers' route selection was specified with the types of traffic information and the expected travel time to examine the influence on the selection of drivers' route. The model was estimated and analyzed in three types according to the condition of detour roads, and the rate of route change and the degree of sensitivity was calculated from the estimation. The results of analysis are as follows. the $1^{st}$ type model showed the 10% of route change for the travel time saving of 5minutes, and the 81.6% of route change for the travel time saving of 20minutes. The $2^{nd}$ type led to the range of route change from 14.2% to 92.7% over the 5 through 20 minutes of travel time saving. The $3^{rd}$ model resulted in the 99.1% of route change. The sensitivity of route change showed the highest for the travel time saving of 11 minutes with the $1^{st}$ type model, 9 minutes with the $2^{nd}$ type model, and 5 minutes with the $3^{rd}$ type model respectively.

• Journal of Korean Society of Transportation
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• v.29 no.6
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• pp.97-106
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• 2011

Mode choice model is an essential element for estimating- the demand of new means of transportation in the planning stage as well as in the establishment phase. In general, current demand analysis model developed for the mode choice analysis applies common parameters of utility function in each region which causes inaccuracy in forecasting mode choice behavior. Several critical problems from using common parameters are: a common parameter set can not reflect different distribution of coefficient for travel time and travel cost by different population. Consequently, the resulting model fails to accurately explain policy variables such as travel time and travel cost. In particular, the nonlinear logit model applied to aggregation data is vulnerable to the aggregation error. The purpose of this paper is to consider the regional characteristics by adopting the parameters fitted to each area, so as to reduce prediction errors and enhance accuracy of the resulting mode choice model. In order to estimate parameter of each area, this study used Household Travel Survey Data of Metropolitan Transportation Authority. For the verification of the model, the value of time by marginal rate of substitution is evaluated and statistical test for resulting coefficients is also carried out. In order to crosscheck the applicability and reliability of the model, changes in mode choice are analyzed when Seoul subway line 9 is newly opened and the results are compared with those from the existing model developed without considering the regional characteristics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.667-677
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• 2013

The introduction of a new transit facility affects mode share of travel alternatives. The multinomial logit model, which has been the most commonly used for estimating mode share, has difficulty in reflecting heterogeneity of travelers' choices, and it has a limitation on grasping their characteristics of mode choice. The limitation may lead to over- or under-estimation of the new transit facility and bring about significant social costs. This paper aims to find a methodology to overcome the problem of preference homogeneity. It also applies market segmentation structure of separating the whole population into direct and indirect beneficiary to consider their preference heterogeneity. A mode choice model is estimated on data from Jeju Province and statistically tested. The results show that mode transfer rate of direct beneficiaries that inhabit in downtown areas increases as the new transit facility provides more advanced services with higher costs. The results and the model suggested in this study can contribute to improving the accuracy of demand forecasting of new transit facilities by reflecting heterogeneity of mode-transfer patterns.

• KDI Journal of Economic Policy
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• v.26 no.1
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• pp.71-104
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• 2004

This paper explores the empirical performances of the workout companies with special interests in the effectiveness of corporate reorganizing tools on their revitalization. In the empirical analysis it considers the criteria of success or failure in restructuring from both creditors' and debtors' perspectives. The key results are summarized as follows. First, the initial conditions on the debt structure of the workout companies are significantly related to the revitalization from both creditors' and debtors' point of view. Second, the debt restructuring instruments are insignificant in the success of corporate turnarounds while the debt-to-equity conversion has been a relatively effective tool. Third, the self-restructuring efforts, employment downsizing and governance reshuffling do not affect the performances significantly. The higher importance of initial conditions than corporate restructuring efforts may imply that Korean corporate workouts serve better to the needs of creditor financial institutions which are to maximize debt recovery and of the government which is to overcome financial crisis.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.512-512
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• 2009

본 연구는 자유지방산을 포함하고 있는 저품위 유지로부터 바이오디젤을 합성하는데 있어서 외부가열 방법 대신에 마이크로파를 이용한 내부 직접가열 방법으로 고체촉매 반응을 가속화한 연구에 관한 것이다. 대두유를 원료로 KOH 균일촉매를 이용한 전이에스테르화 실험에서는 섭씨 60도 상압조건에서 반응시간 3분에 95.4%의 전환율을 획득했다. 올레산과 고체산촉매를 이용한 자유지방산 제거 실험에서는 섭씨 60도 상압조건에서 solvent free 방식의 S-ZrO2는 반응시간 20분만에 93.7%의 제거율을 보였고 Rohm&Hass사의 Amberlyst-15dry 촉매는 반응시간 30분에 82.0%의 제거율을 보였다. 또한 바이오디젤 합성에 사용된 마이크로파의 총 에너지를 측정한 결과 외부가열 방법에 비해 약 1/3 수준임을 확인했다. 이것은 기존의 heat bath를 이용한 실험결과들과 비교할 때 반응속도가 약 10배 정도 향상되면서도 에너지효율이 높다는 것을 확인한 결과로서, 저품위 유지를 원료로 하는 바이오디젤 생산공정에서 마이크로파가 매우 효율적인 가열수단이 될 수 있음을 보여주었다.