Simulating trips and their outcomes at the transportation system level

Travel demand in POLARIS arises from a series of individual behaviors relating to generating, planning and scheduling both routine and day-to-day activity engagement and travel (see Figure 1). The interaction of the travel demand model that generates the activity engagement (LINK) with the transportation supply model that simulates the trips in the network and their outcomes. From the results, the network performance characteristics is processed to create the metrics of interest when analyzing new technologies.

Figure 1. Transportation supply

Multi-modal transportation networks

  • Roadway links by facility type (expressway, arterial, collector, local…)
  • Walkway links for non-motorized modes and connectivity to other modes
  • Transit stops, routes, patterns, etc by mode (bus, subway, rail…)
  • Traffic management infrastructure, including signals, signs, sensors, communication
  • Parking infrastructure

Movements and operations of multiple transportation service providers

  • Transit schedules and capacitated individual vehicle movements
  • Fleet vehicles for mobility service providers (rideshare, bikeshare, carshare, eScooter)
  • Fleet operations for mobility providers (repositioning, rebalancing, ridematching…)
Figure 2. Transportation supply data elements in POLARIS.

Key features of traffic flow and transportation simulation in POLARIS

  • Cutting edge agent-based implementation of mesoscopic traffic flow based on LWR model includes node model for flows at signalized and unsignalized turn movements
  • Time-Dependent Intermodal A* algorithm for agent-based shortest-path calculations paired with a unique information mixing model for fast dynamic traffic assignment convergence
  • Connection to optimization models for implementing fleet and infrastructure controls within the POLARIS simulator
  • Fully multi-modal routing and travel simulation allows agents to switch between modes as needed for more realistic trip simulation
  • Advanced vehicle technologies, such as cooperative-adaptive cruise control, platooning, vehicle-to-infrastructure connectivity able to be represented in meso-scopic simulation