• 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 Korean Society of Transportation
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• v.23 no.2
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• pp.143-150
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• 2005

Estimation of trip distribution, estimated O-D matrix must satisfy the condition that the sum of trips in a row should equal the trip production, and the sum of trips in a column should equal the trip attraction. In most cases the iterative calculation for convergence is needed to satisfy this condition. Most of all present convergence of iterative methods may results a big difference between estimated value and converged value, and from this, the trip distribution patterns may be changed. This paper presents a new convergence of iterative method that comes closer to meeting the convergence condition and gives the maximum likelihood estimation for calculating a distribution patterns from the trip distribution estimation model. The newly developed method differs from existing methods in three important ways. First, it simultaneously considers both the convergence condition and the distribution patterns. Second, it computers simultaneous convergence of rows and columns instead of iterating respectively. Third, instead of using the growth rates to the trip production, trip attraction, it uses the differences between trip production and sum of trips in a row, and trip attraction and sum of trips in a column. Using 38 by 38 O-D matrix, this paper compared the Fratar method and the Furness method to the newly developed method and found that this method was superior to the other two methods.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3D
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• pp.417-424
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• 2006

To get more accurate trip distribution estimation results, this study developed an improved gravity model. Using three different year's O-D table resulted from person trip survey, this study analyzed correlative between basic year's residuals and target year's residuals by gravity model. And resulted that the two have linear correlation. From this, improved gravity model was developed as adding basic year's residual to present gravity model. Developed gravity model was compared to present gravity model by estimation accuracy, and revealed that distributed trips from improved gravity model was more closer to real O-D than distributed trips from present gravity model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5D
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• pp.763-769
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• 2006

Gravity Model estimates target year's distributed trips using three variables like as origin zone's trip production, destination zone's trip attraction and traffic impedance between origin zone centroid and destination zone centroid. Estimating inner zone trip by gravity model is impossible because traffic impedance of inner zone has "0" value. So till today, for estimating inner zone trips, other methods like growth factor model are used. This study proposed inner zone trip estimation method that calculates inner zone's traffic impedance using established gravity model and estimates inner zone trips by putting calculated traffic impedance into the gravity model. 1988 year's surveyed O-D as basic year's O-D, proposed method's and existing methods(growth factor method and regression model)'s estimated results of 1992 year's and 2004 year's were compared with each year's real O-D by $x^2$, RMSE, Correlation coefficient. And resulted that the proposed method is superior than other existing methods.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.287-295
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• 2013

This paper developed advanced gravity model for higher estimation accuracy, that deals with residuals. Previously studied paper using gravity model's residual, residual calculated that observed O-D value minus derived O-D value from gravity model, and this residual added to the target year's estimated value from gravity model. In this paper, residuals calculated on gravity model parameter estimation process, and this residual is revealed the same value that observed O-D value devided by derived O-D value from gravity model. And case study resulted that developed new gravity model that applied accordance rate of observed O-D value and derived O-D value from gravity model has higher estimation accuracy than other gravity models as basic gravity model and residual plused gravity model.

• Journal of Korean Society of Transportation
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• v.31 no.2
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• pp.60-68
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• 2013

This study developed plural gravity models and their application method in order to increase the accuracy of trip distribution estimation. The developed method initially involves utilizing the coefficient of determination ($R^2$) to set the target level. Afterwards, the gravity model is created, and if the gravity model's coefficient of determination is satisfactory in regards to the target level, the model creation is complete and future trip distribution estimation is calculated. If the coefficient of determination is not on par with the target level, the zone pair with the largest standardized residual is removed from the model until the target level is obtained. In respect to the model, the removed zone pairs are divided into positive(+) and negative(-) sides. In each of these sides, gravity models are made until the target level is reached. If there are no more zone pairs to remove, the model making process concludes, and future trip distribution estimation is calculated. The newly developed plural gravity model and application method was adopted for 42 zone pairs as a case study. The existing method of utilizing only one gravity model exhibited a coefficient of determination value ($R^2$) of 51.3%, however, the newly developed method produced three gravity models, and exhibited a coefficient of determination value ($R^2$) of over 90%. Also, the accuracy of the future trip distribution estimation was found to be higher than the existing method.