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Flow

For Facility-Based projects, the data inputs in the Flow tab indicate the fractional share of travel – measured by fraction of trips – taking place within, going out of, going into, or passing through the Region of the data row.

For O-D Based projects, all the columns in this tab will be grayed out, as they are not valid.

Data Fields

All fields are to be entered as fractions, and thus must be entered as a number from 0 to 1.

  • Internal Trips begin and end within the Region. All of their traveler benefits and all of the economic impacts are within the Region.

  • Incoming Trips originate outside the Region but end within it. Half of their traveler benefits and economic impacts are within the Region.

  • Outgoing Trips originate within the Region but end externally. Half of their traveler benefits and economic impacts are within the Region.

  • Through Trips have both their origin and destinations outside the Region, so that vehicles pass through the region (and use the travel facility) but do not stop there. None of their traveler benefits or economic impacts are within the Region.

In addition to determining where benefits and impacts are felt, for freight modes, the flow shares are used to match commodity costs to industries based on whether the commodities are being imported or exported. Incoming freight trips are matched to industries that use the commodities being shipped, whereas outgoing trips are matched to industries that produce the commodities being shipped. Internal trips are split between users and producers).

If the sum of the 4 shares in a row does not equal exactly 1.0000, you will get an error when you click Save and your changes will be lost for any rows where they don't sum correctly.

Example

Consider the following example.

Example Inputs on the Flow Tab
Example Inputs on the Flow Tab

The entered data for Passenger Car mean the following:

  • 50% of trips take place within the Boston Region.
  • 20% of trips end in Boston Region but originated externally.
  • 20% of trips start in Boston Region but end externally.
  • 10% of trips pass through Boston Region and don't stop.