A departure is a way to tell RIFE to reset all global variables. A typical example of when is this is useful is when logging out from a site, and having RIFE automatically reset the authentication id variable. Instead of having to do it manually with code in the elements, you just set up a departure:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE site SYSTEM "/dtd/site.dtd">

<site>

  <globalvar name="authid"/>

  <element name="HOME" file="home.xml" url="/home"/>
  <element name="LOGGED_OUT" file="logged_out.xml" url="/logged_out"/>

  <departure srcid="LOGGED_OUT"/>
</site>    

Note that in contrast to arrival which you can only specify once per site definition there can be several departures.