In addition to the relative amounts of trips between an Origin-Destination pair, we also provide the relative amounts of total trips for each Zone used in the Project. The values are calculated differently depending on whether a Zone is an Origin Zone or Destination Zone, and whether the Zone is designated as "Pass-Through" or not. We include these values because it can be useful to understand, for example, out of all the trips starting in Origin Zone A, what percent stop in each of 3 Destination Zones (B, C and D). To calculate this, you would look at the Origin Zone Traffic value for Zone A and then compare with the Origin-Destination Traffic for each O-D Pair (A-B, A-C, A-D). For example, the Origin Zone Traffic value is 1000, and the Origin-Destination Traffic is 100, 300 and 250, for O-D pairs A-B, A-C, A-D, respectively. Then you know that out of all the trips starting in Zone A, 10% end in Zone B, 30% end in Zone C, 25% end in Zone D, and the remaining 35% end someplace else.
- Origin-Destination Trip Index values represent the volume of trips from the Origin Zone to the Destination Zone.
- Origin Zone Trip Index values represent all trips from the Origin Zone with no limitation on where they went.
- Destination Zone Trip Index values represent all trips to the Destination Zone with no limitation on where they came from.
If the Zone has an "Is Pass-Through" value of yes, then the Index values will only reflect trips that pass through the Zone. Otherwise, the Index values represent trips starting in Origin Zones and ending in Destination Zones.