Proportional distribution of demand

1. Make sure, that - for zones to be regarded with proportional demand distribution during assignment - the attribute SharePrTOrig and/or SharePrTDest has been set to 1 (yes).

Note: For the origin and/or destination connectors of these zones, you need to specify weights (Connectors: Basis tab).

2. From the Calculate menu, choose General procedure settings.

The General procedure settings window opens.

3. In the navigator, click PrT settings > Connectors.

4. Make the desired setting in the Default method for connector shares section:

Element	Description
Default method for connector shares	Apply to total origin/destination demand (percentage connectors) (percentage connectors) If this option is selected, MPA is not calculated. The entire origin and destination demand of the zone originating from the assigned PrT destination demand is used proportional to the current connector weights as connector capacity in the volume-delay function of the connectors (Fundamentals: Distribution of demand of a zone to the connectors). Note Connector impedances depend on the connector volumes. Apply to each single OD pair (MPA, multi point assignment) If this option is selected, MPA is calculated. The demand of any OD pair between zones is distributed to all available connectors proportionally to their weights (Fundamentals: Distribution of demand of a zone to the connectors). Note Connector impedances do not depend on the connector volumes.

Element

Description

Default method for connector shares

Apply to total origin/destination demand (percentage connectors) (percentage connectors)

If this option is selected, MPA is not calculated.

The entire origin and destination demand of the zone originating from the assigned PrT destination demand is used proportional to the current connector weights as connector capacity in the volume-delay function of the connectors (Fundamentals: Distribution of demand of a zone to the connectors).

Note

Connector impedances depend on the connector volumes.

Apply to each single OD pair (MPA, multi point assignment)

If this option is selected, MPA is calculated.

The demand of any OD pair between zones is distributed to all available connectors proportionally to their weights (Fundamentals: Distribution of demand of a zone to the connectors).

Note

Connector impedances do not depend on the connector volumes.

Notes: Multi-point assignment (MPA) can be used with an PrT assignment procedure. MPA always works symmetrically, thus only OD pairs with proportional demand distribution to the origin zone connectors and to the destination zone connectors are concerned. Thus, the user has a choice for every zone and direction whether to apply MPA or not.

The default method has been selected.

5. In the VD function for percentage connectors section, select an appropriate volume-delay function as default method for zones with proportional demand distribution to connectors (Allocating a VDF to proportional connectors without MPA).

This VDF is used only for zone connectors with proportional distribution of the total origin/destination demand.

6. Confirm with OK.

The settings are applied.

7. Make sure that the attribute Method for connector shares has been set to 0 (Default) for all proportionally connected zones to which the selected method is to be applied during assignment.

For these zones, the default method is used.

8. If applicable, change the method for individual zones: Set the attribute Method for connector shares to 1 (Each single OD pair) or 2 (Total trips (MPA off)).

For those zones, the default method is replaced by the method selected for this particular zone.

For all zones with demand distribution by shares, the next PrT assignment will use the method allocated to the zone by direction of the connector.