A model can be introduced as a schematic description of a real-world system, theory, or phenomenon that accounts for its known or inferred properties used for further study of its characteristics or to predict or evaluate the intrinsic dynamic behavior. In the transportation system sector, models or systems of models (so-called models of models (MOM)) are used to simulate traffic performance and traffic flow. Incorporating traffic requirements, as defined by technical and/or
organizational constraints of real-world transportation systems, these models are used to predict impacts and/or to evaluate possible options for transportation planning and evaluation.
Transportation planning is defined as the process of making decisions about transportation resource needs, preferences, and values. Planning occurs at many different levels from day-to-day decisions to more general major decisions to strategic decisions with long-term impacts. Best practices in transportation planning can be achieved by coordinating short-term decisions in support of strategic long-term goals. An example of such comprehensive planning is transportation infrastructure planning with regard to land use, economic development, and social planning. Another example would be when manifold potential options exist to reduce traffic congestion, and some of these solutions may also help to overcome other traffic problems, such as finding parking spots and minimizing pollution emissions. A comprehensive transportation planning process will result in the prioritization of transportation activities and the efficient allocation of resources. In the evaluation of transportation planning activities, the evaluation itself can be used as a method of determining the value of a potential planning option in order to support decision making. That is why evaluation in transportation planning is often applied when it comes to decision making and there are specific evaluation methods used, such as:
• Cost-effectiveness (CE): This method compares the costs of different potential options for achieving a specific objective, such as building a particular highway or delivering a particular amount of airfreight, etc. The quantity of benefits (outputs) are held constant, so there is only one variable, the cost of inputs.
• Cost-benefit analysis (CBA): This method compares the total incremental benefits with the total incremental costs for each of the potential options. This analysis is not limited to a single benefit or objective, such as potential highway routes which can differ in construction costs as well as quality of the services offered.
• Lifecycle cost analysis (LCA): This method incorporates, in addition to CBA, the value of investments at the respective schedule, which allows a comparison of projects with regard to their cost and benefit milestones.
• Multiple accounts evaluation (MAE): This method considers quantitative and qualitative evaluation criteria and can be used in cases where some impacts cannot be financially benchmarked. Using this evaluation method each potential option is rated for each potential criterion.
Reference: Introduction to Transportation Analysis, Modeling and Simulation;
Authors: Möller, Dietmar P.F.