• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.189-197
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• 1999

To investigate internal waves (IW) effect on acoustic wave propagation, m analysis is conducted on mode travel time and model simulation. Based on the thermistor string data, it can be shown that the thermocline depth variation may cause travel time difference as much as 4-10 ms between mode 1 and 2 over range 10 km. This travel time difference causes interference among modes and thus fluctuation from range-independent stratified ocean structure. In real situations, however, there exist additionally spatial variation of IW. Model simulation with all modes and simple IW shows clear responses of acoustic signals to IW, amplitude and phase fluctuation.

• Journal of the Korean Society for Railway
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• v.16 no.5
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• pp.418-429
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• 2013

This study assesses the appropriate amounts and applicable ranges of travel time values for freight transport modes in Korea. The findings suggest that it is possible to determine appropriate sizes and applicable ranges of travel time values of goods set for road transport mode (i.e. truck), whereas those for railway, inland waterway, marine, and air transport modes are not as easily estimated. The adequate travel time value for trucks is 20,000won/vehicle hour, and the application range of travel time value of trucks is 17,000~23,000won/vehicle hour considering other variables. The most adequate estimation method of determining the travel time value for road transport is the wage rate method, whereas the marginal rate of substitution method is more rational for railway, inland waterway, marine, and air transport modes considering the application purpose and characteristics of the goods transported.

• Journal of Korean Society of Transportation
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• v.4 no.1
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• pp.12-27
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• 1986

This study examined user preferences toward transportation modes in Seoul. Two multidimensional scaling models, the ideal point and vector models, were applied to data on mode preferences of 114 adults in the metropolitan area. While both models produced fairly similar results, the vector model performed slightly better than the other in terms of interpretability of the results. The transport attributes elicited are comfort, flexibility, travel cost, travel time, privacy, and safety; among which comfort is salient most. The comfort variable is a multi-faceted attribute in nature. The variations of attribute preferences are most significant between the gender groups as well as worker/nonworker groups. In particular, male workers, female workers and female nonworkers form three distinctive market segments. An unidimensional scaling of the preference data reveals that subway, auto-driver, and subscription bus modes are preferred most, whereas motorcycle and bicycle least. The other modes of express bus, taxt, auto-passenger, bus and walk rank intermediately. An examination of how preference orders vary among modal groups hints that users align their stated attitudes to their choice in order to reduce cognitive dissonance.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.2297-2302
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• 2010

The status and effectiveness of Bi-modal Tram is analyzed through the comparison of the transport effectiveness and operation cost between the public transportation systems (bus, light rail transit) considering the vehicle and operation characteristic of new transit system Bi-modal Tram. The standard operation schedule is established in consideration of the vehicle specification and operation characteristic of main public transportation modes, and then the annual average operation cost is estimated depending on the volume, speed, analysis length for respective public transportation mode. Through analyzing the operation cost and distribution characteristic of public transportation modes depending on the transport volume and travel speed, the operational efficiency suitable for the city is derived. It is concluded that the operational efficiency of Bi-modal Tram is superior to that of the bus and light rail transit on the aspect of travel volume and operation speed.

• Journal of Korean Society of Transportation
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• v.11 no.2
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• pp.5-26
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• 1993

In order to analyze travel mode choice behavior, behavioral models including logit model, based on revealed preference theory, have been using easily measurable variables such as individual socioeconomic characteristics and physical attributes of travel modes. But some recent attitudinal models of travel choice behavior have implied that the negligence of individual psychological variables and individual choice constraints in travel mode choice might preclude better prediction of individual travel mode choice behavior. In this context, this study was attempted to reconstruct an attitudinal model(AM), especially focused on the decision rules in travel mode choice decision making process, consistent with the conceptual framework relating individual attitude and choice constraints to choice behavior. And to evaluate the strengths of the AM to other comparative models(logit, linear-additive, conjunctive, lexicographic model) in predicting travel mode choice bebavior, an empirical study of the mode choice in work-trip to CBD in Seoul was performed. According to the results the percent of correct prediction(PCP) derived from the AM was higher than those derived from comparative models by at least 7 to 20% in predicting travel mode choice. But each model produced a different prediction accuracy depending on market segmentation by travel modal users, individual socioeconomic characteristics, transportation system characteristics, and satisfaction levels. The finding that different groups divided by a certain criterion employ different decision rules supports the necessity of developing a choice model such as the AM combining compensatory and noncompensatory decision rules, and suggests that a proposed transportation system management plan or policy may have different effects on each group.

• The Journal of the Acoustical Society of Korea
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• v.18 no.3E
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• pp.9-20
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• 1999

To investigate the characteristics of internal waves (IWs) and their effects on acoustic wave propagation, a series of sea experiment were performed in the east coast of Donghae city, Korea in 1997 and 1998 where the water depth varies between 130 and 140 m. Thermistor strings were deployed to measure water temperatures simultaneously at 9 depths. CW source signals with the frequencies of 250,670 and 1000 Hz were received by an array of 15 hydrophones. Through the Wavelet transform analysis, the IWs are characterized as having typical periods of 2-17 min and duration of 1-2 hours. The IWs exist in a group of periods rather than in one period. Underwater acoustic signals also show obvious energy peaks in the periods of less than 12 min. Consistency in the periods of the two physical processes implies that acoustic waves react to the IWs through some mechanisms like mode interference and travel time fluctuation. Based on the thermistor string data, mode arriving structures are analyzed. As thermocline depth varies with time, it may cause travel time difference as much as 4-10 ms between mode 1 and 2 over 10 km range. This travel time difference causes interference among modes and thus fluctuation from range-independent stratified ocean structure. In real situations, however, there exist additional spatial variation of IWs. Model simulations with all modes and simple IWs show clear responses of acoustic signals to the IWs, i.e., fluctuations of amplitude and phase.

• Proceedings of the KOR-KST Conference
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• 2003.02a
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• pp.127-150
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• 2003

This research presents a novel application of static traffic assignment methods, but with a variable time value, for estimating the market share of a high-speed rail (HSR) in the NW-SE corridor of Korea which is currently served by the airline (AR), conventional rail (CR), and highway (HWY) modes. The proposed model employs the time-space network structure to capture the interrelations among all competing transportation modes, and to reflect their supply- and demand-sides constraints as well as interactions through properly formulated link-node structures. The embedded cost function for each network link offers the flexibility for incorporating all associated factors, such as travel time and fare, in the model computation, and enables the use of a distribution rather than a constant to represent the time-value variation among all transportation mode users. To realistically capture the tripmakers' value-of-time (VOT) along the target area, a novel method for VOT calibration has been developed with aggregate demand information and key system performance data from the target area. Under the assumption that intercity tripmakers often have nearly "perfect" travel information, one can solve the market share of each mode after operations of HSR for each O-D pair under the time-dependent demand with state-of-the-art traffic assignment. Aside from estimating new market share, this paper also investigated the impacts of HSR on other existing transportation modes.

• Journal of Biosystems Engineering
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• v.27 no.5
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• pp.409-416
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• 2002

This study was conducted to develop a vehicle, leading or following a worker at a certain distance to assist laborious transporting works in greenhouses. A prototype vehicle, which consisted of the rear driving, the front steering and the console units, was designed and tested in the ideal indoor conditions. Results of this study were summarized as following: 1. The driving unit was designed to travel at the speed ranges of 0.3∼0.8 m/sec depending on the operating modes with a maximum payload of 100 kg. 2. The console unit consisted of a main-board including a 80C196KC microprocessor and peripheral devices, a power-board and safety interlock. Worker-leading, and following modes were available in automatic and manual modes. 3. Steering was achieved by turning the steering motor against the sensed direction. Proper steering angles for correcting travel direction were determined as 5 and 9 degrees when sensing cultivation beds and plants, respectively.

• Journal of the Korean Operations Research and Management Science Society
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• v.3 no.1
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• pp.31-46
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• 1978

Consider a time interval during which the demand for trips is fixed (e.g. the rush hour period). The traveller has a choice between various public modes, whose travel times and fares are fixed, and the automobile mode, for which travel time and cost depend on the volume of traffic flow on those roads, which are subject to congestion. We consider the equilibrium in terms of a representative travellerm, who choses for any trip the mode and route with the least combined money and time cost. When several (parallel) model or routes are chosen, then the combined cost of money and time must be equal among these. Our problem is first, to find the optimal flows of cars and of public mode carriers on the various links of their networks and second the optimal fares for trips by the variousmodes. The object is to minimize the total operating costs of the carriers and car plus the total time costs to travellers. The optimal fares are related to, but not identical with the dual variables of the underlying Nonlinear Program. They are equal to these dual variables only in the case, when congestion tolls on trips or on the use of specific roads are collected from automobile users. When such tolls are not collected, they must be passed on as subsidies to travellers using competing modes. The optimal fares of public modes are then reduced by the amounts of these subsidies. Note that subsidies are not a flat payment to public carriers, but are calculated on the basis of tickets sold. Fares and subsidies depend in general on tile period considered. They will be higher during periods of higher demand. When the assumption of fixed trip demand is relaxed, this tare system is no longer best, but only second best since too much traffic will, in general, be generated. The Free Rider Theorem states the following : Suppose road tolls can be charged, so that a best pricing system for public modes is posssible. Then there may exist free rides on some routes and modes, but never on a complete round trip.

• Land and Housing Review
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• v.14 no.4
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• pp.77-93
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• 2023

The COVID-19 pandemic has brought about significant social changes through government prevention and control measures, changes in people's risk perceptions, and lifestyle changes. In response, urban inhabitants changed their behaviors significantly, including their preferences for transportation modes and urban spaces in response to government quarantine policies and concerns over the potential risk of infection in urban spaces. These changes may have long-lasting effects on urban spaces beyond the COVID-19 pandemic or they may evolve and develop new forms. Therefore, this study aims to explore the potential for urban spaces to adapt to the present and future pandemics by examining changes in urban residents' preferences in travel modes and urban space use due to the COVID-19 pandemic. This study found that overall preferences for travel modes and urban spaces significantly differ between the pre-pandemic, pandemic, and post-pandemic periods. During the pandemic, preferences for travel modes and urban spaces has decreased, except for privately owned vehicles and green spaces, which are perceived to be safe from transmission, show more favorable than others. Post-pandemic preferences for travel modes and urban spaces are less favorable than pre-pandemic with urban spaces being five times less favorable than transportation. Although green spaces and medical facilities that were positively perceived during the pandemic are expected to return to the pre-pandemic preference level, other factors of urban spaces are facing a new-normal. The findings suggest that the COVID-19 pandemic has had a significant impact on urban residents' preferences for travel modes and urban space use. Understanding these changes is crucial for developing strategies to adapt to present and future pandemics and improve urban resilience.