Switches and sidings allow other trains to pass. Trains can be reconfigured on one of the two sidings or wait for another train to go by. Cooperative play with other engineers at the table is required.
The module could be made flat - and doing so simplifies construction. But adding a half-ramp up and/or down for the sidings makes it much more interesting. A few trim cuts to avoid gaps around the double crossovers may be necessary. Still, this is an easy project.