it helps show that the product is safe for both people and earth. cycle simulation therefore runs at a constant speed, regardless of activity in the model. the widest section is a two and a half mile span. another rail bridge crosses the tail race canal less than a mile below the dam. full-page strips were eventually replaced by strips half that size. there is often a section of wood between the rail and the playing surface; this is called the "race track" and often features cup holders as well. 