• Journal of Korean Society of Transportation
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• v.29 no.4
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• pp.85-93
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• 2011

Many policies, such as transit-oriented development, encouraged use of bicycle and pedestrian, reduction of green house gas (GHG) and etc., have been deployed to support transport sustainability. Although various studies regarding GHG were presented, no one has yet adequately explained the behavior of travelers. This paper proposes a GHG emission model by highlighting its sensitivity, elasticity with regard to such travel cost as travel time, travel fare, and GHG pricing, introduced to reduce the amount of GHG in transportation system. For better estimation of GHG, the proposed model adopts (1) a production-constrained gravity model and (2) the travel distance from the origin and the destination (OD). The gravity model has a merit that it considers travel pattern between OD pairs. The model was tested with an example, and the promising results confirmed its validation and applications.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.5
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• pp.591-596
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• 2018

In Designing a Small Ship, the Design of the Trim for Sailing has a great influence on the Stability of the Ship as well as Resistance. The Center of Gravity of a Ship is mostly determined during Initial Design. This Study confirms the Effect of Trim on changes in Vertical Center of Gravity by Numerical Analysis for a Small Catamaran. The Results were examined in a Model test. However, No Model tests were conducted while varying the changes in Vertical Center of Gravity. Nonetheless, Investigation was completed for the Purpose of presenting Vertical Center of Gravity results according to plans for the Trim during Initial Design of a Small Ship. In order to verify the Results of Numerical Analysis, a Comparison with Experimental results was carried out. Alternation of Trim angle and Resistance performance according to changes in the Center of Gravity were studied.

• Journal of the Economic Geographical Society of Korea
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• v.13 no.3
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• pp.457-469
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• 2010

The study aims to estimate interregional trade coefficient of service industry using the gravity model. The gravity model has been widely used for prediction of the level of human interaction between two regions which is positively related to attraction of them and negatively related to the distance between them. To apply the gravity model for explaining the interregional trade flow of service industry, the choice of proper proxy variables which represent a dependent variable and independent variables is most important. However, the literature shows that there are few studies on this issue. Four models concerned to the choice of proxy variables are considered. Finally, this paper employs the least-squares regression analysis to test the model's goodness-of-fit, and suggests the most appropriate model based on the result from the analysis. The result shows that the interregional trade of service industry in regional input-output table developed by The Bank of Korea is desirable as a dependent variable, the service industry output of export region, the population of import region, and the spatial distance between regions are desirable as independent variables.

• International Journal of Highway Engineering
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• v.18 no.2
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• pp.91-101
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• 2016

PURPOSES : The aim of this study was to compare the performance of the QUEENSOD method and the gravity model in estimating Origin-Destination (O/D) tables for a large-sized microscopic traffic simulation network. METHODS : In this study, an expressway network was simulated using the microscopic traffic simulation model, VISSIM. The gravity model and QUEENSOD method were used to estimate the O/D pairs between internal and between external zones. RESULTS: After obtaining estimations of the O/D table by using both the gravity model and the QUEENSOD method, the value of the root mean square error (RMSE) for O/D pairs between internal zones were compared. For the gravity model and the QUEENSOD method, the RMSE obtained were 386.0 and 241.2, respectively. The O/D tables estimated using both methods were then entered into the VISSIM networks and calibrated with measured travel time. The resulting estimated travel times were then compared. For the gravity model and the QUEENSOD method, the estimated travel times showed 1.16% and 0.45% deviation from the surveyed travel time, respectively. CONCLUSIONS : In building a large-sized microscopic traffic simulation network, an O/D matrix is essential in order to produce reliable analysis results. When link counts from diverse ITS facilities are available, the QUEENSOD method outperforms the gravity model.

• Journal of Korean Society of Transportation
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• v.33 no.4
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• pp.393-404
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• 2015

Gravity model has had the major problem that the model explains the characteristics of travel behavior with only deterrence factors such as travel time or cost. In modern society, travel behavior can be affected not only deterrence factors but also zonal characteristics or transportation service. Therefore, those features have to be considered to estimate the future travel demand accurately. In this regard, there are two primary aims of this study: 1. to identify the characteristics of inter-zonal travel, 2. to develop the new type of calibration method. By employing accessibility variable which can explain the manifold pattern of trip, we define the zonal travel behavior newly. Furthermore, we suggest 2-phase calibration method, since existing calibration method cannot find the optimum solution when organizing the deterrence function with the new variables. The new method proceeds with 2 steps; step 1.estimating deterrence parameter, step 2. finding balancing factors. The validation results with RMSE, E-norm, C.R show that this study model explains the inter-zonal travel pattern adequately and estimate the O/D pairs precisely than existing gravity model. Especially, the problem with estimation of short distance trip is overcomed. In conclusion, it is possible to draw the conclusion that this study suggests the possibility of improvement for trip distribution model.

• Journal of Korean Society of Transportation
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• v.30 no.5
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• pp.43-59
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• 2012

It is generally assumed about trip distribution estimation model that growth factor model's estimation accuracy is higher than that of other models in short-term and that gravity model's estimation accuracy is higher than that of other models in long-term. For validation of such assumptions, this study compares estimation accuracies of each estimation model using 3year(1988, 1992, 2004) O-D tables from Daegu city. Each estimation model's accuracy were compared by mid-size and large-size zone as well as short-term and long-term target years. The results show that the trip distribution estimation model selection by usual assumption is not always right.

• Journal of Distribution Science
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• v.6 no.1
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• pp.47-62
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• 2008

Joining the WTO in 2001, China became a number of the global economic system. China succeeded in vying to host Beijing 2008 Olympic Games and World Expo 2010 Shanghai. It is China's honor and opportunity to have high economic growth in the coming future. In 2007, the total cost of public logistics decreased by 18.2% than 2006 to 4540.6 billion RMB, accounting for 18.4% of the GDP. So, China logistics is a huge industry and a growing market full of charm. The statistic ratios of China's logistics and growth trends show us it is an important issue to build and run an effective logistics system. However, research on China's logistics systems and supply chain is lacked. This study is focus on the logistic location strategy in China including the study of factories and warehouses geographic strategy concerned with SCM. The core of this study is to propose a New Multi-Facilities Location Decision Model. This study banded the revised gravity center, the standard single facility location decision model(Gravity Center Model) and the transportation model into a new Multi-Facilities Location Decision Model. In addition, this study suggested the gravity center of population, the gravity center of each industry, the location decision graded-list of each industry of china using the gravity center model and the revised gravity center model. The new Multi-Facilities Location Decision Model proposed in this study can be used to solve the location decision problem of more than two facilities. And it can be used in the fields such as the location decision of production facility and service facility, the location of distribution and logistics, the location of broadcast and satellite communications, the location of wireless communication tower and so on.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1799-1810
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• 2011

Origin-Destination(OD) trip survey being used in travel demand forecasting has been obtained through totalizing process with direct sample survey techniques such as plate license survey, roadside interview, household travel survey, and cordon line counts. However, the OD survey has many discrepancies in sampling, totalizing process, and such discrepancies contains problems of difference between forecasted traffic volume and observed data. On the other hand, transit smart card data recently collected has credible resource of obtaining travel information for bus and metro. This paper presents parameter estimation of gravity model by using transit smart card data. Through the parameter estimation method, we estimated =0.57, ${\beta}$=0.14 of gravity model for bus, and ${\alpha}$=-0.21, ${\beta}$=0.05 for metro. The statistical test such as T-test, coefficient of correlation, Theil`s inequality coefficient showed no difference between observed volume and estimated volume. Elasticities of bus and metro derived in this paper are also reasonable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.617-631
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• 2019

In the four-step demand model, a gravity mode is used most commonly at the trip distribution stage. The purpose of this study was to develop a new friction factor that can express the accessibility property as a single friction factor to compensate for the variable limits of the gravity model parameters (travel time, travel cost). To derive a new friction factor, a new friction factor was derived using the space syntax that can quantify the characteristics of the urban space structure, deriving the link-unit integration degree and then using the travel time and travel distance relationship. Calibration of the derived friction factor resulted in a similar level to that of the existing friction factor. As a result of verifying the various indicators, the explanatory power was found to be excellent in the short - and long - distance range. Therefore, it is possible to derive and apply the new friction factor using the integration index, which can complement the accessibility beyond the limit of the existing shortest distance, and it is believed to be more advantageous in future utilization.

• Journal of Korean Society of Transportation
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• v.11 no.1
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• pp.55-66
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• 1993

본 논문에서는 최근에 소개된 일반화중력모형(Generalized Gravity Model)파라메터의 최우추정치(Maximum Likelihood Estimates) 계산을 위한 새로운 알고리즘을 이론적으로 도출하였다. 개발된 알고리즘은 첫째 계산속도, 둘째 정밀도, 셋째 모형변수(예컨데 통행시간, 통행비용 등)들 간에 공선성(multicolinearity)이 존재할 경우의 계산능력, 넷째 대규모 스케일의 기.종점자료(large O-D Matrices)에 적용시의 계산능력, 다섯째 모형변수의 개수에 따른 계산능력의 평가기준에서 그 계산실적이 기존의 알고리즘과 비교 평가 되었다. 제안된 기법중에서 Modified Scoring 기법은 계산속도 및 정밀도등 앞서 나열한 계산능력의 평가기준 중 모든 부문에서 매우 탁월한 계산실적을 보이는 것으로 판명되었다. 따라서 최선의 추정치를 보장하는 최우추정기법이 대규모 스케일의 교통계획 적용에도 큰 비용(시간)부담없이 손쉽게 적용될 수 있게 되었다. 제안된 새로운 알고리즘의 적용시 교통계획분야에 가져올 수 있는 기대효과는 다음과 같다. 첫째, 최우추정법이 대규모 O-D 통행표에 쉽게 적용될 수 있고 또한 PC등 소형 컴퓨터에서도 처리가 쉽다. 둘째, 모형설명변수의 자유로운 선택등 통계적실험(experimentation)을 가능케 한다. 셋째, 중력모형이 내재되어 있는 결합모형(Combined Model)의 정산속도를 높인다. 넷째, IVHS(Intelligent Vehicle and Highway System)와 같은 분야에서 온라인(On-line)모형정산을 가능케 할 수 있다.