Route Switching Model

Instead of choosing their paths at each intersection, vehicles can also be assigned pre-specified paths to their destinations. However, they can switch to alternative routes (e.g., an incident is viewed or delay information is obtained from ATIS) at intermediate nodes. The simulator reads a list of predefined paths from a path table file. Each path is defined by an unique ID and a list of links it consists of. The expected travel time on the path is also included. The route switching model defined below is used for choosing an initial route and en-routing vehicles:

where:

p(s|r,t)

probability to choose path s for a vehicle that expects to arrive at the decision node at time t using path r;

set of available paths from node j to the driver's destination;

systematic utility of choosing path i which is a function of:

expected time on path i at time t; and,

diversion penalty if path i is different from the driver's current path r (or habitual path).

Based on the probabilities calculated from (Eq 3.8), a random number is drawn to determine whether the vehicle should stay on its current path or switch to an alternative path.