Related Terms

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.

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.

kirchoff model

An alternative formulation to the path-size logit model which considers the relative size of the total utilities of the path. For example, deltas of short paths are perceived differently than deltas on long paths. For paths that are generally the same size, the results will be similar to a logit model formulation.

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.

path choice model

A mathematical model for selecting a path from a set of feasible choices. Examples include the recursive logit model, path-size logit model, Kirchhoff model.

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).

pathfinding probability

The probability of each path in the pathset based on the pathfinding cost. Differs from simulated probability in that the simulation step hasn’t occurred yet so the probabilities are subject to change; for example, some paths may become infeasible if the simulation fills up some vehicles so the the passenger cannot board the vehicle for this leg. May also include path overlap penalties (although Fast-Trips doesn’t calculate it in Pathfinding, only in Simulation).

joint person tour

A set of paths between an origin and destination with specific costs, waypoints, and timings. In hyperpath-based frameworks this is often derived from the hyperpath.

predicted passenger path choice set links

A list of links for a predicted path set/hyperpath, with their timing and costs, that the passenger considers taking.

predicted passenger path choice set

A list of feasible paths, with their timing and costs, that the passenger considers taking for a specific trip. In some frameworks, hyperpaths can be used to create the path choice set.

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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