The Analytical Process
The process that is taking place during the design or operational analysis of traffic components can be described well by the flow chart shown in the figure below. The performance of a traffic system component is estimated based on a set of inputs, i.e., traffic demand, traffic control and transport supply, to some analytical model. Transport supply (i.e., capacities or minimum headways) is affected by the employed traffic control, which in turn can be modified to achieve the desirable level of performance. The performance of the system may be expressed in terms of user of system performance indices such as speeds, delays, queue lengths, traffic density levels, environmental consequences, etc. The conversion of the demand, supply and control characteristics to performance indices can be achieved only by understanding the interactions among them. These interactions are formulated in the analytical model which depending on the complexity of the application can vary from a simple equation to a very sophisticated traffic simulation model.
Figure 1.1
