The mode choice procedure is part of the 4-step model with sequential calculation of the steps. The single-step mode choice breaks down the total demand (total demand matrix) into the individual transport modes per demand stratum (for example PrT, PuT) based on mode-specific impedance skims (for journey time, costs, etc.).
First of all for each mode m the utility is calculated as a linear combination of the impedance parameters.
where
|
cijmg |
The impedance of the cost type g for the trip from zone i to zone j by mode m. |
The respective shares of the trips of each relation result from the utilities of the different modes. Hereby, you can choose between several distribution functions (Gravity model calculation). As an example see below the calculation for the Logit model.
whereby Tij is the total number of trips of the demand stratum in the relation i-j, Tijm is the number of trips made by mode m and c is a procedure parameter.
There are two types of demand strata.
- Those referring directly to a demand matrix allocated to one single demand segment or several demand segments
- Those whose demand matrix is not related to any demand segment
No mode choice will be calculated for demand strata referring directly to a matrix with demand segment(s).
For demand strata whose demand matrix is not related to any demand segment it is determined per mode to which demand matrix the demand allocated to that mode has to be added in mode choice.
