Demand Scenarios

Scenarios contain the information Podaris needs in order to create agents and generate/assign trips.

demand scenario

There are two types of scenarios you can create:

Query - allows you to use flexible and powerful GIS-like queries to select origins and destinations from datasets. This could be used to look at journeys between population data and points of interest.
Origin Destination - allows you to define an exact number of people who travel from an origin point/station in the project, to a destination point/station in the project. This can use the output csv files from strategic demand models to carry out further analysis.

Query

Type	Agent: This means that the trip generates an associated population. It can be thought of as defining a trip from where someone actually lives. Occupant: These types of trips are based on current occupancy of their origins - if there are no agents currently there, no trips can occur. These are mainly used for intraday movements. The number of trips can never exceed the number of agents currently at the destination.
No. of Trips	The number of trips controls how many people will attempt to make trips between the matched origin and destinations. You can define the number of trips as: Total: this will be split evenly across all origins matched Total per entity: this will set a static number of trips for each origin matched. Total per pair: the number of trips to generate for each origin-destination combination. From Attribute: this will allow you to select a numeric attribute and set the number of trips as a percentage of that value for each origin. Current Occupancy: this allows you select a percentage of the current number of agents at each origin when the trip takes place
Archetype	The archetype to use for calculating the mode preferences for each of the possible trips.
Allowed modes	By default trip definitions will always try to use all possible transport modes, and will then select the mode choice based on the mode preferences. Here you can disable certain modes from being considered, useful when modelling travellers with mode-impairments or lack of access.
Time distribution	Trips will receive random start times within the ‘Start’ and ‘End’ times specified in the from section. How those times are dispersed are based on the distribution selected and peak time set. We currently support the following distributions: Uniform (when selected the peak time is not used) Triangular Beta-PERT
Max duration	This sets the maximum travel time someone is prepared to take for a trip. If the journey duration is greater than this, the trip does not happen.
Destination weight	This allows you to choose how trips are distributed across the matched destinations. If even is selected, each destination will receive the same number of trips. However, when you select capacity you will have the option of choosing a numeric attribute to be used as the capacity value for each destination. Trips will then be assigned to destinations in proportion to their capacity.
Polygon coordinates	When polygons are found as part of the from or to queries, the actual coordinate used for the trip can either be the centroid or a random point within the polygon.
From: / To:	Origins and destinations are selected by running a query against the attributes of all the visible layers. The possible options are mostly self-explanatory, and the queries can be as complex or simple as you would like. If the same entity is both a destination and origin, trips may still be assigned to it, however they will have a duration and distance of zero.
Time	The start and end time for the trips, along with the peak time can be set. Trips will then be distributed across this time based on the time distribution settings.