Thomas is headed to action canyon and you get to decide whether the bridge is up or down when he gets there. Press the RIGHT ARROW and LEFT ARROW on your keyboard to move Thomas back and forth. When Thomas gets to the bridge, press the DOWN ARROW on your keyboard to drop the bridge!
Source
http://www.thomastrackmaster.com/thomas-trackmaster-actCanGame.html (via Wayback Machine)
Thomas at Action Canyon screenshots
I love thomas