Capacity analysis and planning is the process through which the most dependable and economical method of operating a given railroad infrastructure is determined.
The problems manifested on a daily basis may not necessarily be those that need to be solved. For example, if the main line between East Terminal and West Terminal is experiencing congestion, but the traffic level is higher than can be absorbed by East Terminal, congestion might be eliminated or at least reduced by planning operation around the capacity of East Terminal.
Infrastructure is expensive. Getting the most benefit from capital dollars requires careful planning. Adding a second main track for a short distance may eliminate delays at that location only to move the delays to the real source of capacity limitation at some distant point. Adding capacity to East Terminal will solve congestion problems only until the capacity of East Terminal exceeds that of the surrounding infrastructure. The excess capacity at East Terminal represents capital that would have been better used for another purpose.
Scheduling is the planning part of capacity analysis. Schedule refers not only to transit time and delivery information provided to customers but also to the operating plan of the railroad. Scheduling is Resource Allocation. Aside from the need to provide customers with transit and delivery time information, only with unlimited resources does scheduling become unnecessary. Unless resources are unlimited, operation will be affected by availability of locomotives, cars, personnel, and infrastructure. Even random operation of trains becomes a schedule driven by resource limitations.
The railroad infrastructure may not be able to produce results defined by a market driven schedule, resulting in delays, expense, and dissatisfied customers. The one hour photo finishing shop can produce your photographs in one hour only when business levels are low enough to ensure that each machine and person required for the process is available when necessary to provide 1 hour service, regardless of the fact that 1 hour service is advertised in order to be competitive. A commercial printer, on the other hand, will consider the availability of equipment and personnel for each phase of your job and provide a delivery date. The delivery time promised will be developed through scheduling each step of the process in order to produce the product on the delivery date without a last minute crisis and the profit-reducing expense of overtime and equipment rental, or subcontracting. Just as in the commercial print shop, schedule analysis is used to investigate each step required to provide transportation. Schedule analysis can be static as in the development of the operating plan and the customer schedules, or it can be dynamic as in creating the plan necessary to recover from unforeseen events ranging from an on-line mechanical failure to a derailment or natural event that results in closure of the line for a period of time. The result is the schedule or operating plan that can be reliably met at the least expense.
Unlike passenger customers that relate directly to individual trains and schedules by boarding a specific train at a specific time at a specific station, most freight customers relate only to the time that they must have the car ready for the railroad to remove from their facility and the time and day that the car will be ready for unloading at the other end of the trip. Service planning involves establishing a series of connecting events that produce the two events about which the customer cares. In order for the goal origin and destination times to be accurate, the underlying system of train and yard events on which the car events depend must viable and accurate.
Simulation modeling is the tool used in capacity planning and analysis. Depending on the nature and complexity of the problem and the infrastructure involved, simulation modeling may be as simple as the use of paper and pencil to keep track of the process, as complex as the use of simple or sophisticated computer programs, or may involve some combination of both methods.
Simulation modeling is the only way in which each step of the transportation process can be included in the plan.
The work of a train dispatcher is both static and dynamic capacity and schedule analysis as well as plan development and execution. A large portion of train dispatcher training involves the strategy and tactics of railroad operation, the effect of various resource limitations, the analysis of operating situations, and the creation of plans that provide the most economical and efficient solution. Computer simulation models attempt to duplicate or at least emulate the mental process of a train dispatcher in order to provide a tool that can be used to assist in solving problems larger in scope than those that can be efficiently solved mentally or with the use of simple tools.