After figuring out how many trips are made, what planning step connects where trips start to where they go?

The planning step that connects where trips start to where they go, after figuring out how many trips are made, is Trip Distribution. Trip Distribution takes the total number of trips generated by each origin zone and the total number of trips attracted to each destination zone and matches them. An origin zone is a specific geographic area from which trips begin, such as a residential neighborhood. A destination zone is a specific geographic area where trips end, such as a commercial district or an industrial park. This step's purpose is to determine the number of trips that flow from each specific origin zone to each specific destination zone within the study area. For instance, it calculates how many daily trips originate from a particular suburb (an origin zone) and are destined for a specific downtown office complex (a destination zone). A common mathematical approach used for this is the Gravity Model, which posits that the number of trips between two zones is directly proportional to the 'mass' or attractiveness of the destination (e.g., its employment or population) and inversely proportional to the 'friction' or impedance (e.g., travel time or distance) between the origin and destination. The primary output of the Trip Distribution step is a trip table, also known as an Origin-Destination (O-D) matrix, which is a comprehensive table showing the number of trips from every origin zone to every destination zone.