7. Analytical Models and Techniques

Traffic models can be very useful in the enhancement of complex transportation systems, as well as in their management and evaluation. They can help in the design and operations of traffic systems since they can predict traffic operational conditions at some time in the future under various sets of design, traffic, and control characteristics. Traffic engineers and designers can make decisions regarding facility modifications or traffic management improvements based on the expected impact of those improvements on the transportation system. Traffic models can also help in the evaluation of existing systems and in the development of priorities for improvement. Some mathematical models are based on theoretical principles. For example: Flow = Speed × Density is a mathematical model based on the fundamental principles of traffic flow. On the other hand, empirical models are those based on field observations (empirical observations) rather than on relationships that can be mathematically described. Empirical models predict how a system behaves rather than explaining how its components interact. Empirical models can be useful when the mathematical relationship is unknown or difficult to express. Examples of empirical models are the traffic stream relationships discussed in Chap. 3.