Demand for Shared Mobility Services#
POLARIS is an end-to-end activity-based agent-based workflow. For a given model area, the target population can be synthesised, following demand generation that can then feed into the shared mobility module to evaluate service measures. The modular nature of POLARIS, however, allows users of the shared mobility module two options with regards to demand:
Synthetically Generated Demand#
Agents synthesized during a POLARIS simulation utilize the activity-based modeling workflow to determine the set of activities to perform during the day. Through a series of mode, destination, timing, and other choices, traveler agents determine to use a shared mobility service to reach their destination and partake in their activity. As demand and supply and intricately interwoven, the ability to choose a shared mobility mode such as travel by a TNC vehicle requires both that the service provider is providing a service from the intended origin to destination, and also that the quality of the service provided is appealing enough (cost and time compared to other modes) for the option to be chosen. A series of iterations can be run with synthesized demand so that service quality and traveler preference to use the service converge to a stable point.
The use case of using synthesized demand is particularly important for users and operators that would like to forecast demand for a planned service, size fleets based on forecasted profitability, and track service quality across a variety of measures given the region’s travel patterns and interest to utilize the planned service.
Using Exogenous Demand#
In addition to the activity-based workflow, POLARIS also includes agent-based dynamic traffic assignment and users may want to particularly leverage the network simulation and supply-side modeling of fleets and its operational policies. In such cases, demand for shared mobility services can be obtained from real world data in the form of trip requests. These trip requests can then be conflated with the POLARIS regional model so that a POLARIS Trip dataset is created. Records in the trip table includes informaiton on start time, origin, destination, and the mode chosen. For the purposes of using the shared mobility module, this can include background traffic or trips that make requests to the shared mobility module. This fixed set of trips can then be simulated through POLARIS to determine the service quality, network and policy impacts arising just from the different settings and strategies that can be enforced on the fleet within the simulation.
Simulating such exogenous demand through POLARIS can be beneficial in evaluating service quality and network effects, and provides a unique way to do apples-to-apples comparison by reducing the dimensions of variability. However, it does limit users from understanding latent demand for such a service in the region as all demand remains fixed as an input.
For a detailed description of simulating fixed exogenous demand using POLARIS, please visit the Fixed Demand page.
Types of Demand Supported#
POLARIS currently supports the following types of demand for simulation with auto-based services such as TNCs: - Passenger demand (traveler requests pickup and dropoff, with or without sharing a ride, with or without preferences) - Meals and grocery demand (households order meals and grocery for delivery to their homes, either in advance or on-demand) - E-scooter rebalancing (e-scooter companies can use a fleet of vehicles to rebalance e-scooters at different times of day)
The following multimodal options are also supported (more details available in the FMLM section): - First-mile-last-mile transit trips: can include walk or e-scooter access/egress from a bus/train station - First-mile-last-mile parking trips: includes e-scooter access/egress to and from parking location based on dynamic availability of e-scooters at specific parking location
Demand arising from a variety of sources as described above are all passed on to providers through a Request object that can hold information of the type, preferences, and needs of the shared mobility trip that the traveler/household/company needs to undertake. A detailed description of the available fields are documented in the Request page. For a description of supported service modes, check the Service Modes section.
All or type-specific requests may be shared, or pooled, across operators that support pooling. Demand-related decisions on whether or not a request wants to pool can be modeled through survey-based econometric outcomes. Several pooling models are available and can be used based on the users’ requirement. In lieu of making assumptions on individual pooling behavior, setting DRS_FLAG = true allows all requests to be conidered for pooling. Visit the Pooling Choice section for overviews and references to pooling.