dispersion parameter
Used for modeling stochasticity. This parameter is between 0 and 1. Higher values for the parameter mean that higher cost links within a hyperlink are devalued compared to the lowest cost links in the hyperlink. That is, if the lowest cost for a hyperlink is c, when a new link gets added to the hyperlink with a cost higher than c, when θ is closer to 1, the more the new link has a low probability compared to the lowest cost link. The higher θ emphasizes the lowest cost link more.
Related Terms
hyperpath cost
The disutility of a specific hyperpath or portion thereof for a specific user class. Based on both link features, path features, and the path weight parameters.
link feature
A feature that can be accurately represented for an individual link (e.g. in-vehicle-time, wait-time, walk-time). Some features, like fares, can be represented at a link level, but may not be accurate if used without understanding of the entire path due to dependent features such as maximum fares or transfers.
overlap scale parameter
The parameter in the path-size logit model that scales the impact of the path size term.
person-trips
A list of person trips with information required to assign them to vehicles.
path feature
Feature of a path that is summarized for the entire path. Can be an aggregation of the link features comprising the path (i.e. wait-time), or a variable that can only be calculated at the level of the entire path (e.g. fare, directness).
path weight parameters
Coefficients on various components of the utility equation for the path choice model. Can be estimated, asserted, or inferred. Path weight parameters can either be based on a link feature (i.e. in-vehicle time) or path feature (i.e. directness). The path weight parameters can vary by user class.
user classes
Passenger market segments who use the same parameters (including path weight parameters) to find and assess paths. Common user class segmentations are by travel purpose and captive versus choice users.
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