Sketch-level or macroscopic analysis looks at deterministic relationships between traffic variables such as flow, speed, and density to evaluate segment operations (FHWA Traffic Analysis Toolbox Volume II: Decision Support Methodology for Selecting Traffic Analysis Tools). Deterministic means that for a set of inputs, there is only one answer. In this context, it means the characteristics of individual vehicles are not tracked on the system-wide level. Performance measures are aggregated for platoons of vehicles over specified time intervals. Network details are approximated or based on averages.

Sketch-level or macroscopic analysis is supported by observed patterns of traffic variables. Sketch-level or macroscopic analysis tools typically need the least amount of input and detail and are often used for projects in the planning stage of project development or for projects that do not need high levels of detail. Sketch-level or macroscopic analyses are typically used for analyzing a large network, or screening multiple alternatives. It is not well suited for analyzing unique transportation networks. If a network is considerably modified from the original demand or network attributes, obtain new OD tables before analyzing it.

The purpose of this section is to provide an overview of the tools available to complete a Sketch-level or macroscopic analysis and provide guidance on when to use the different tools, the data and input needed for each tool, and the MOEs used to evaluate operations.

TDM and service volume tables are the main tools used analyze segments at a Sketch-level or macroscopic level. The outputs of a TDM are typically used if the segment to analyze is available in the model. In some instances, TDM provides a more detailed analysis than is necessary for the project stage or scope, in which case the service volume tables can be used. Service volume tables are discussed in depth below.