• International Journal of Railway
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• v.7 no.1
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• pp.24-33
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• 2014

The Korean high-speed rail (HSR) began its commercial service in 2004. This service has been created significant changes in the system of intercity passenger travels of Korea. However, the actual ridership was approximately half of the estimated one in the planning stage. In this background, this paper presents the difference between the stated preference (SP) before the HSR service and the revealed preference (RP) after it using the intercity travel mode choice models. Several meaningful differences are found in terms of the factors affecting the travel mode choice, the estimation results of model, the monetary values of time, and elasticities. While the access/egress travel time of high-speed rail is less important than in-vehicle travel time in the SP sample, they have same weight in the RP sample. Also the RP models show that the probability of choosing HSR can be decreased by the increase of the number of vehicles in household contrary to the results from the SP models. The monetary values of travel time are relatively high and the direct and cross elasticities in response to changes in level-of-service of HSR are relatively low in the RP sample. This Korean case is expected to offer referable material for preparing high-speed rail services in other countries by showing the difference between the SP and RP before/after the actual service, identifying the importance of access/egress travel time and lower direct elasticities of HSR demand.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.2
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• pp.14-26
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• 2009

This study presented a novel method to estimate travel times under incident conditions. Predictive travel time information was defined and evaluated with the proposed method. The proposed method utilized individual vehicle speeds obtained from global positioning systems (GPS) and inter-vehicle communications(IVC) for more reliable real-time travel times. Individual vehicle trajectory data were extracted from microscopic traffic simulations using AIMSUN. Market penetration rates (MPR) and IVC ranges were explored with the accuracy of travel times. Relationship among travel time accuracy, IVC ranges, and MPR were further identified using regression analyses. The outcomes of this study would be useful to derive functional requirements associated with traffic information systems under forthcoming ubiquitous transportation environment

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.43-50
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• 2011

The monitoring system for link travel speed using taxi probe is one of key sub-systems of ITS. Link travel speed collected by taxi probe has been widely employed for both monitoring the traffic states of urban road network and providing real-time travel time information. When sample size of taxi probe is small and link travel time is longer than a length of time interval to collect travel speed data, and in turn the missing state is inevitable. Under this missing state, link travel speed data is real-timely not collected. This missing state changes from single to multiple time intervals. Existing single interval prediction techniques can not generate multiple future states. For this reason, it is necessary to replace multiple missing states with the estimations generated by multi-interval prediction method. In this study, a multi-interval prediction method to generate the speed estimations of single and multiple future time step is introduced overcoming the shortcomings of short-term techniques. The model is developed based on Non-Parametric Regression (NPR), and outperformed single-interval prediction methods in terms of prediction accuracy in spite of multi-interval prediction scheme.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.3 no.2 s.5
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• pp.129-140
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• 2004

In this paper, we conduct the research about optimal aggregation interval of travel time data on interrupted traffic flow and verify the reliability of AVI collected data by using car plate matching method in RTMS for systematic collection and analysis of link travel time data on interrupted traffic flow rural arterial. We perform Kolmosorov-Smirnov test on AVT collected sample data and on entire population data, and conclude that the sample data does not represent pure random sampling and hence includes sample collection error. We suggest that additional review is necessary to investigate the effectiveness of AVI collected sample data as link representative data. We also develop statistical model by applying two estimation techniques namely point estimation and interval estimation for calculating optimal aggregation interval. We have implemented our model and determine that point estimate is preferable over interval estimate for exactly selecting and deciding optimal aggregation interval. Our final conclusion is that 5-minute aggregation interval is optimal to estimate travel time in RTMS, as is currently being used our investigation is based on AVI data collected from Yang-ji to Yong-in $42^{nd}$ National road.

• Journal of Korean Society of Transportation
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• v.26 no.3
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• pp.199-209
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• 2008

This paper is described the concepts and limitations for the traditional directional design hour volume estimation. The main objective of this paper is to establish an estimation method of probabilistic directional design hour volume in order to improve the limitation for the traditional approach method. To express the traffic congestion of specific road segment, this paper proposed the link travel time as the probability that the road capacity can accommodate a certain traffic demand at desired service level. Also, the link travel time threshold was derived from chance-constrained stochastic model. Such successive probabilistic process could determine optimal ranked design hour volume and directional design hour volume. Therefore, the probabilistic directional design hour volume can consider the traffic congestion and economic aspect in road planning and design stage. It is hoped that this study will provide a better understanding of various issues involved in the short term prediction of directional design hourly volume on different types of roads.

• Journal of Korean Society of Transportation
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• v.23 no.3 s.81
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• pp.109-123
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• 2005

The goals of this paper are two folds: i) to evaluate whether the data collected by a license plate matching AVI equipment being operated on some segment of a national highway are suitable or not for use in travel time estimation of interrupted traffic flows; ii) to study the statistical methodologies to be used for the determination of the optimal aggregation interval for travel time estimation. In this study it was found that the AVI data are not representative because the data are collected on some selected lanes of a roadway where main traffic is thru-traffic and, thus the AVI data are different from those collected from all lanes in traffic characteristics. For the determination of the optimal aggregation interval for travel time estimation. two statistical methods. namely point estimation and interval estimation. were tested. The test shows that the point estimation method is more sensitive and gives more desirable results in determing the optimal aggregation interval than the interval estimation method. And it turned out that the optimal aggregation interval on interrupted traffic flows has been calculated as 5 minute and thus the existing aggregation interval. 5 minute is proper.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.1
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• pp.79-88
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• 2018

With the increasing popularity of electronic toll collection system using 5.8 GHz dedicated short-range communications (DSRC) technology, DSRC-based travel-time collection systems have been deployed on major urban and rural arterial routes in Korea. However, since probe sample sizes are frequently insufficient in probe-based systems, the gathered travel times from probe vehicles fluctuate significantly compared to those of the population; as a result, the accuracy of the collected travel times could decrease. To mitigate the fluctuations (also known as biases), smoothing techniques need to be applied. In this study, some smoothing techniques-moving average, the Loess, and Savitzky-Golay filtering-were applied to probe travel times. Resultantly, the error in the smoothed travel times at the lowest sampling plan (5%) decreased as much as 45% compared to those in non-smoothed travel times. The results of this study can be practically applied to probe-based travel-time estimation systems for providing reliable travel times along the travel corridor.

• Geophysics and Geophysical Exploration
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• v.6 no.2
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• pp.71-76
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• 2003

Accurate estimation of the first arrival travel time is an essential task to obtain a high resolution velocity tomogram. Accuracy of the travel time estimation may be influenced by two factors; geological and mechanical. A serious mechanical factor is the source firing control problems. We found the control problems in the records generated by tome impulsive borehole sources. The problems are; irregular firing control and uncertainty in estimation of the absolute firing-times shown in records. Definitely, the time difference will introduce an error to the first arrival times, and accordingly; it will cause some distortion in the resulting velocity tomogram. A method to determine the firing time is suggested here. The method determines the optimum onset time by comparing the horizontal and the NMO velocity with various amount of delay time adjustment.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.2
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• pp.34-44
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• 2007

Many urban cities deployed ITS technologies to improve the efficiency of traffic operation and management including a real-time franc control system (i.e., COSMOS). The system adopted loop detector system to collect traffic information such as volume, occupancy time, degree of saturation, and queue length. This paper investigated the applicability of detector information within COSMOS to represent the congestion level of the links. Initially, link travel times obtained from the field study were related with each of detector information. Results showed that queue length was highly correlated with link travel time, and direct link travel time estimation using the spot speed data produced high estimation error rates. From this analysis, a procedure was proposed to estimate congestion level of the links using both degree of saturation and queue length information.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.288-298
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• 2017

The system of high-speed and conventional railway vehicles is diversified, and significant technological development in performance has been achieved. This study analyzed the modal change characteristics; furthermore, it estimated the value of travel time by improving the travel time and cost for the passenger's perception of railway. In this study, we formulate a mode choice model for passengers and compare it with the mixed logit model which reflects individual taste variation. In addition, the validity of the analysis is presented through an estimation the value of travel time using the derived model. For this purpose, a stated preference survey was conducted with 510 people using public transportation. The benefits of time-saving can be accurately determined by estimating the value of time spent on the railway. Appropriate fares for public transportation can also be estimated.