How to Improvise an op session or How to run like the real railroads. There are two types of traffic, scheduled and unscheduled. Scheduled traffic is very easy to handle. It consists of everything listed in the switch list. Unscheduled traffic is a little more difficult to handle.
Yardmasters have a number of decisions to make about how to handle traffic that is in their yard.
If during the day a large number of cars arrive for the local industries then the yardmaster may need to schedule an extra to handle the traffic. Most locals should be kept relatively small, about 7-12 cars in length. If, for example there are 30 cars for the Troy Bennington run, the yardmaster can create an extra to deliver the cars. This way two small trains are sent out as opposed to one large train. All extras must be cleared with the dispatcher before they are sent out.