In mobility simulation modeling, routing is by far the most computationally expensive aspect of the model. Each route represents a solution to a recursively evaluated dynamic programming problem which, depending on the distance of the trip, requires processing a very large fraction of the total transportation network. Every agent in BEAM chooses between trip alternatives in a multimodal context. Essentially, the agents use a trip planning app which allows them to tradeoff their preferences between time, cost, and convenience. This occurs millions of times every day in an urban region, so our routing solution needs to be highly scalable.
This is why we are excited to be partnering with Conveyal to use their open source routing tools as the backbone for multimodal routing in BEAM. Conveyal is the maker of Open Trip Planner and R5, two platforms that allow agents in BEAM to evaluate a menu of mobility options for each trip. As our collaboration moves forward in the coming months, we will update this blog with technical details on how both Conveyal's tools are being used in BEAM.