1. You never trigger the event "onTravelScreenStart".
2. If you don't need the event to be triggered from the server-side, you don't need to set second parameter of addEvent to true.
3. You never call "manageTravelScreenStop".
4. DirectX functions need to be updated every frame, so you must use onClientRender event.
@Razor., that has nothing to do, he's not declaring the variable twice (well, actually he is, but before the end of the value assignment to the variable, the old variable is still "active" so it's like if he is just modifying the value of the variable).