Modeling the use of paths and of combined modes of transport is an integral part of many transport models. The most prominent example is the modeling of Park + Ride trips, during which people use PrT or PuT for part of their path. P+R trips represent a special mode in demand calculation.
- Skim matrices include the costs and/or the utility of path legs derived thereof. In addition, a vol/cap ratio independent component is used that reflects use of the P+R parking lot.
- For an OD pair, there are multiple parking lots to choose from.
- The parking lots have capacities that in combination with VD function they are assigned are essential for choosing a P+R parking lot.
- The path legs are accounted for separately during demand assignment of the respective transport system.
This means that e.g. in a standard 4-step model, additional procedure steps are required in which parking lots are selected. Based on this information, utility matrices for the mode P+R are then calculated per demand stratum. Before assignments are performed, the P+R- total demand is to be distributed across the demand matrices for PrT and PuT, taking into account the P+R lots selected. The total of P+R paths calculated can be saved and displayed as path sequences. Path sequences are data structures reserved for applications with multimodal paths. Park + Ride presents a special case. (P+R procedures and path sequences)
The procedures of P + R calculation are included in the 4-step model as follows:
1. Calculation of PrT and PuT skim matrices and utility per demand stratum
2. P+R lot choice for calculating P+R skims
3. Mode choice
4. P+R lot choice for calculating the distribution of P+R demand across P+R parking lots
5. P+R leg split
6. PrT and PuT assignment
7. If required, Go to the procedure step 1.
This list is limited to the steps required for modeling Park + Ride trips. Other procedures, such as the calculation of trip distribution or the averaging of demand and skim matrices are not explicitly listed.
Distribution of the demand across the parking lots and calculation of the combined skim matrices are performed within the procedure P+R lot choice. The procedure referred to in step 2, P+R lot choice, only determines P+R utility. Distribution of the demand across the P+R parking lots is not dealt with in this step. In general, when performing this step for the first time, there is no P+R demand data available. In any additional iterations - the procedure must be defined within the feedback loop - the utility is determined based on the updated utility of private transport and the distribution of P+R demand across the P+R parking lots. The utilities determined in this step are then used as input data for mode choice calculation.
The Park + Ride demand calculated as a result of mode choice is then distributed across the P+R parking lots during the procedure P+R lot choice. As a result of the procedure, path sequences are created that can be used to display P+R lot choice. Path sequences can be saved separately, by direction, to two different path sequence sets.
During P+R partial leg split and based on the saved data structures, demand matrices are created as path legs and are added to the respective assignment matrices for PrT or PuT.
The two procedures for modeling Park + Ride trips are described in detail (Park + Ride lot choice and Park + Ride leg split).
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Note: In the directory C:\Users\Public\Documents\PTV Vision\PTV Visum 2022/Examples you will find various examples of use for modeling P+R in different demand model types. |
