This is a simulation demo we assembled to test out our new FStEng state engine in ActionScript 2.0, as well as new AS 2.0 components. While it only took us a few hours to make the traffic light, we ended up spending the majority of our time on the car behavior and car-to-car interaction.

*** THIS EXAMPLE REQUIRES THE FLASH PLAYER 7 ***

It started from Miro Samek's C/C++ Users Journal column on state machines (June 2003), in which he describes a traffic light accompanied by a pedestrian crossing mechanism. We implemented that statechart, and then went a little overboard (okay, a lot overboard) on the traffic.

We decided to implement the traffic light and pedestrian crossing using our state engine, but implement the car behavior using Samek's QHsm (AS 2.0) implementation. We started by designing the traffic light system using our XML-to-Statechart code tool. Click here to see the XML for the traffic light system.

The system looked so lonely without traffic to manage, so we decided to implement basic traffic. It occurred to us that we could describe the behavior of a car using state machines. Ultimately, one could describe different kinds of driving styles by inheriting from a default car behavior (state machine). Because this is a great example for inheriting behavior, we used Miro Samek's QHsm framework to describe the cars. Click here to see the original XML for the car (we subsequently modified it, particularly adding more events, but it is essentially the same as what is running in the movie).

For simplicity, when the light turns red, all cars in front of the traffic light stop where they are.

Extra: If you'd like to see how the traffic light is working with respect to states, click here to view the page with the run-time state visualization tool.

You can allow pedestrians to cross (though there are none) by pressing the button on either side of the crosswalk. Use the sliders on the right to change the light timing. If you select a car with the mouse, you will see a speedometer appear to show its current speed. If you press "Display Car States", the cars will show which state they are in (Stopped, Cruising, Accelerating, or Decelerating).