On this page and its subpages, you define the settings for the use of capacity restrictions, and the use of a sharing transport system or the use of demand responsive transport (DRT) in the assignment (Fundamentals: Capacity restriction). Capacity restrictions model the passengers' discomfort which are not taken into account if just the standard settings for the timetable-based assignment are used.
In all the use cases mentioned, the assignment is carried out iteratively.
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Element |
Description |
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Use capacity constrains for vehicle journeys |
If the option is selected, capacity constraints are taken into account in the calculation and you can choose between two options: Soft capacity constraint If this option is selected, a capacity-restricted assignment is performed. Further parameters can be set on the pages Iterations (Timetable-based assignment: Iterations page), Vol/cap ratio dependent impedance vehicle journeys (Timetable-based assignment: Vol/cap ratio-dependent impedance vehicle journeys page), Sharing in general (Timetable-based assignment: Sharing in general page), and Vol/cap ratio dependent impedance sharing (Timetable-based assignment: Vol/Cap ratio-dependent impedance sharing page). Fail to board If this option is selected, no access to a connection is possible once the capacity of the connection is exceeded. You can make further settings on the pages Vol/cap ratio dependent impedance vehicle journeys(Timetable-based assignment: Vol/cap ratio-dependent impedance vehicle journeys page)and Fail to board. |
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Use DRT (Demand Responsive Transport) |
If this option is selected, you can calculate public transport assignments in combination with Ride Sharing. Note An assignment with DRT is only possible with a Branch and Bound search. Make sure that the option has been selected (Timetable-based assignment: Search page). |
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Convergence protocol section |
Log convergence If this option has been selected, a protocol file is generated. Click the |
button to select a path and file name.
On this page you define the settings for the search, termination conditions and the smoothing method used.
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Element |
Description |
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Search section |
After the connection search, the demand is assigned successively to the found paths to avoid unrealistic congestion. Number of assigned demand shares In the input field, enter a value for the number of demand shares to be assigned. Number of iterations with path search In the input field, enter a value for the number of iterations for which a path search is to be performed. |
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Termination conditions section |
Maximum number of iterations without a new path search Number of iterations as a termination criterion if the procedure cannot reach convergence with the selected iteration algorithm. The following applies to all OD pairs for the connection volumes B(V,i) at time step i with regard to the smoothed values B*: Formula for the computation of the termination condition. You can adjust a factor for the calculation. |
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Smoothing method section |
Applied smoothing method From the selection list, choose the smoothing method for the calculation.
If the option is selected, the smoothed volume of a connection or at a Sharing station will be calculated from the volumes of the previous iteration. In the formula used to calculate the smoothened vol/cap ratio, you can adjust factor a (Fundamentals: Smoothing).
If the option is selected, a fixed formula is used to calculate the smoothed volume of a connection or at a Sharing station from the volumes of the previous iteration (Fundamentals: Method of Successive Averages (MSA)). |
Timetable-based assignment: Vol/cap ratio-dependent impedance vehicle journeys page
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Element |
Description |
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Total capacity per vehicle journey item |
Click this button to select the attribute, which defines the total capacity of a vehicle journey item. By default, Sum:Vehicle journey sections/Vehicle combination/Total capacity is set. Notes The total capacity is only included in the calculation when using the impedance function DGITM-CGSP (France) . Alternatively, select a user-defined attribute or a formula attribute, which is calculated from the total capacity multiplied by the desired target saturation. Different capacity values by calendar day cannot be defined. |
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Seat capacity per vehicle journey item |
Click this button to select the attribute, which defines the seat capacity of a vehicle journey item. By default, Sum:Using vehicle journey sections/Vehicle combination/Seat capacity is set. Notes Alternatively, select a user-defined attribute or a formula attribute, which is calculated from the number of seats multiplied by the desired target saturation. Different capacity values by calendar day cannot be defined. |
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Applied volume-delay function |
DB If the option is selected, the calculation of the vol/cap ratio-dependent impedance is based on the volume-delay function of the Deutsche Bahn (German rail). In this case, the so-called expected standing minutes (E) are taken into account (Fundamentals: Calculation of Vol/Cap ratio-dependent impedances). Note The expected standing minutes (E) are the mean value of the minutes a passenger has no seat during his journey if the seats are randomly provided to passengers on each stop-stop relation. In the formula used to calculate the smoothened impedance, you can adjust these factors. SBB If the option is selected, the calculation of the vol/cap ratio-dependent impedance will use a penalty function on the basis of the volume-delay function of the SBB (Swiss rail). In the formula used to calculate the vol/cap ratio-dependent impedance, you can adjust these factors (Fundamentals: Calculation of Vol/Cap ratio-dependent impedances). Linear If the option is selected, the vol/cap ratio-dependent impedance will use a penalty function for the linear calculation. In the formula used to calculate the vol/cap ratio-dependent impedance, you can adjust these factors (Fundamentals: Calculation of Vol/Cap ratio-dependent impedances). DGITM-CGSP (France) If the option is selected, the vol/cap ratio-dependent impedance with penalty function is calculated on the basis of the number of seats, the total capacity, and the number of passengers per area among other things (Fundamentals: Calculation of Vol/Cap ratio-dependent impedances). |
Timetable-based assignment: Sharing in general page
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Element |
Description |
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Length of the intervals |
Use the input field to set the length of the intervals for the vol/cap ratio-dependent impedance and the relocation of vehicles. The value indicates how fast vehicles are relocated within the network. The dynamic of the system is modeled this way. The shorter the entered length, the more detailed the result. The assignment takes longer, however. |
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Table of the initial vol/cap ratio of the Sharing transport systems |
Name sharing-TSys Name of the Sharing transport system Initial vol/cap ratio in percent Value for the initial vol/cap ratio of the network and the stations in percent It is used for the first search and for the formation of the initial vol/cap ratio-dependent impedance. Value range: floating-point number 0 to 100. |
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Use travel times of PrT transport systems as sharing travel times |
From the drop-down list in the Name PrT-TSys column, you can allocate a PrT transport system to each sharing transport system in the Name Sharing-TSys column.
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If the option has been selected, the travel times on links, turns, main turns and connectors of the PrT transport systems will be used for the Sharing transport systems belonging to the assigned mode.
If the option has not been selected, the travel times of the Sharing transport systems are used Timetable-based assignment: Vol/Cap ratio-dependent impedance sharing page
On this page, define the impedance function and set the parameters for the computation of the vol/cap ratio-dependent impedance for shared mobility.
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Element |
Description |
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Rental at a station section |
c1 with the default value 30min If no vehicle is available at the station, there is a wait time of 30 min. c2 with the default value 1 If no vehicle is available at the station, there is a wait time of 11min (Fundamentals: Impedance for renting from a station or a zone) Note c1 and c2 must be greater than zero. |
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Return at a station section |
c1 with the default value 30min If the station is full, there is a wait time of 30min. c2 with the default value 1 If no vehicle is available at the station, there is a wait time of 11min (Fundamentals: Impedance for returning a vehicle to a station ) |
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Rental at a zone section |
c1 with the default value 30min If no vehicle is available at a zone, there is a wait time of 30 min. c2 with the default value 1 If no vehicle is available at a zone, there is a wait time of 11min (Fundamentals: Impedance for renting from a station or a zone) Note c1 and c2 must be greater than zero. |
Timetable-based assignment: DRT in general page
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Element |
Description |
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Aggregation section |
Node aggregation You can use the |
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Trip requests section |
Pre-booking time Indication of the time between the start of the trip request and the desired departure time. Specified in minutes. Maximum wait time Indication of the maximum time that passengers of the trip request have to wait. |
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PUDO scheme section |
Permit only active nodes as PUDO points Select this option to assign only active nodes as pickup and dropoff points. |
| Section Factors for the DRT search impedance |
Specification of a factor for the minimum and maximum search impedance, which is used in DRT This prevents that connections are wrongly dominated (Fundamentals: Calculation of the impedance) |
symbol to select a node attribute that specifies the node count used to aggregate the DRT detour factor, the DRT wait time, and the proportion of DRT trip requests that have not been served.|
Note: Please take into account in the analysis that no tour plan is consistent with the paths received from the assignment due to the aggregation within the procedure. |
Timetable-based assignment: DRT initial values page
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Element |
Description |
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Use fixed initial values |
If the option is selected, you can set fixed initial values for the first search: DRT detour factor in first search In the input field, enter a value for the maximum detour a passenger accepts to pick up other passengers on the way. DRT wait time in first search In the input field, enter a value for the maximum accepted wait time for the passenger. |
| Use existing DRT skims (main zone matrices) as initial values | If the option is selected, the corresponding main zone matrices are used as initial values. The attribute that you selected on the DRT in general page under Node aggregation is used as the main zone number. |
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Random seed |
The value initializes the random number generator. Two procedures with the same version file and identical seed random number are run exactly the same way. If the random seed is varied, the stochastic functions are assigned to a different value sequence in Visum, so that the result of distributing the trip requests to the nodes changes. This can lead to different distribution results. |
Timetable-based assignment: DRT output page
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Element |
Description |
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Save DRT skims and DRT demand in main zone matrices |
If the option is selected, the DRT skims and the DRT demand are saved in main zone matrices after the last DRT calculation. The following matrices are created:
The attribute that you selected on the DRT in general page under Node aggregation is used as the main zone number. |
| Directory for saving tour plans | Specification of a directory for storing all tour plans that are calculated in the iterations of the procedure. |
Timetable-based assignment: DRT tours
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Element |
Description |
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Fleet |
Number of vehicles Specify the number of vehicles available Number of seats per vehicle Specify the number of seats per vehicle. |
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Vehicle sharing section |
Multiple trip requests may share a vehicle
Maximum detour factor Specify a factor for the maximum additional time accepted by passengers to serve more than one trip request. Maximum detour time Specify the maximum additional time accepted by passengers that results from servicing more than one trip request. Detour time accepted at all times Specify the lowest limit of additional time that is always accepted when operating a DRT system. |
Timetable-based assignment: DRT tour planning
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Element |
Description |
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Link run times section |
PrT transport system of vehicle fleet You can use the drop-down list to select the transport system to be used for calculating the link run times. |
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Minimize vehicles section |
You can then use the slider to minimize number of vehicles. If you move the slider in the direction of More served trip requests, the number of vehicles required usually increases. If you move the slider in the direction of Less vehicles needed, the number of trip requests is usually reduced. |
Timetable-based assignment: DRT locations page
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Element |
Description |
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Section Holding areas |
Node is holding area Selection of a node attribute that determines whether a node is a holding area. Use holding areas for relocation If the option is selected, holding areas can be used to relocate vehicles. Time of inactivity Input field for the period of inactivity that may elapse before vehicles have to return to the holding area. Use holding areas for start and end of a tour If the option is selected, holding areas can be used to start a tour. You can then select an attribute that contains a Holding area weight. |
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Section Charging areas |
Node is charging area Selection of a node attribute that determines whether a node is a charging area. Maximum range Input field for the maximum range of the e-vehicle Charging duration to 80% Input field for time span required to reach 80% of the charging capacity. Charging duration from 80% to 100% Input field for the additional time span required to reach 100% charging capacity. |
Timetable-based assignment: Impedance DRT supply variability
Enter values for the variables a, b, and c. This will influence the impedance function resulting from the passenger's uncertainty about the quality of service (Fundamentals: Calculation of the impedance).
