A fundamental difference between dynamic and static problems is the evolution of information. In static problems information is assumed to be known for the entire duration of the transportation process. In dynamic problems, however, some input is not known at the time of planning, and some input is not known with certainty. For example, traffic conditions change, the number of vehicles available may change due to vehicle break-down, new transportation requests become known, or attributes of transportation requests may change.
In the collection of fresh milk, for example, pickup locations are generally known in advance and do not change dynamically. However, the amount of milk to be collected may change significantly and is only known with certainty when the vehicle reaches the pickup location. Courier companies face a different challenge: not all customer locations are known when the vehicles start their tours and new transportation requests arrive while the vehicles are en-route.
Another issue in dynamic planning is the reliability of future information. Long-term information is more likely to change than short-term information. For example, long-term estimations of travel times can only be based on historical data. In the short-term, however, actual traffic conditions can be used to estimate travel times. Those short-term forecasts allow a much better estimation of what is going to happen and thus, help in improving punctuality.