Elementary Analysis in Trip Distribution Modeling

A method for manually calibrating the gravity model using elementary analysis is described. Requisite for the method is an O-D matrix, which is first transformed to logarithms before column and row averages are subtracted, resulting in a residuals matrix. The same operation is performed in a matrix of distances yielding a distance residuals matrix. These two residuals are graphed to determine the friction term of the gravity model. This friction factor, computed for a sample from a suburban circumferential corridor, was applied to another sample. Using the gravity model, the O-D matrix is estimated in a straightforward, noniterative manner, yet they are remarkably similar to the actual trip matrix. The method is proposed as a useful trip distribution modeling and forecasting technique, whenever the study is relatively small and quick results are desired. Larger problems may use the same method but require computer analysis.