Trip distribution

The trip distribution procedure is part of the 4-step model with sequential calculation of the steps. The productions and attractions calculated in the trip generation procedure only determine the constraints of the total demand matrix of a demand stratum. The elements of the matrix themselves are calculated in the trip distribution procedure. On the one hand, the allocation of a certain destination zone to a given origin zone is based on its attractiveness for the demand stratum (measured by its destination demand = attractions), on the other hand the impedance of the trip from origin to destination zone is vital (measured by the skim matrices for journey time, fares and other elements of generalized costs).

These input data being available, a gravity model is formulated and solved (Gravity model calculation).

Notes:   Origin and destination traffic of the individual zones have to be available per demand stratum as zone attributes productions and attractions. To each demand stratum for which Trip distribution is to be calculated a demand matrix has to be allocated into which the results are stored. The parameters for the gravity model can be estimated beforehand (Estimating gravitation parameters (KALIBRI)).