What is the P/A to O/D conversion factor for?
In the conventional four-step travel demand modeling process, home-based trips are expressed in what is called “production/attraction” (PA) format, before being converted to “origin/destination” (O/D) format. Home-based P/A tables typically contain two daily trips for each trip-maker, both of which originate at the production zone. These trips represent the trip from home to the attraction (e.g., work, school) and the return trip. When daily trips are in P/A format, the trip maker’s zone of residence is easy to identify. When daily trips are in O/D format, it is difficult to distinguish between trips made by residents and those made by non-residents. The conversion factor allows STEAM to analyze benefits to residents and also to conduct its analysis at the O/D level. If you choose to use this feature, you should use the same conversion factor that your travel demand model uses.
