If they plummet into the river you know you need to go back to the drawing board. The robust physics deployed in the Bridge Construction Set let you build a wide variety of bridges that can span the river.
The 3D graphics allow you to view your bridge from any angle including a first person train view - its like being strapped to the front of the train when your bridge is first tested
The Bridge Construction Set includes many types of bridge building levels in varying degrees of difficulty from simple to complex with a tutorial section to get you started.
A Level Editor is also included so you can create your own levels and trade them with others.