Types of Traffic Analysis Tools
Numerous traffic analysis tools have been developed by public agencies, research organizations, and private vendors/consultants. Traffic analysis tools can be grouped into the following categories:
Sketch-planning methodologies and tools produce general order-of-magnitude estimates of travel demand and traffic operations in response to transportation improvements. They allow for the evaluation of specific projects or alternatives without conducting an in-depth engineering analysis. Therefore, sketch-planning approaches are typically the simplest and least costly of the traffic analysis techniques.
Travel Demand Models
These are mathematical models that forecast long-term future travel demand based on current conditions and future projections of household and employment characteristics. Travel demand models were originally developed to determine the benefits and impact of major highway improvements in metropolitan areas. Travel demand models only have limited capabilities to accurately estimate changes in operational characteristics (such as speed, delay, and queuing) resulting from implementation of ITS/operational strategies.
Analytical/Deterministic Tools (HCM-Based)
Most analytical/deterministic tools implement the procedures of the Highway Capacity Manual (HCM). As such, these tools quickly predict capacity, density, speed, delay, and queuing on a variety of transportation facilities. These tools are good for analyzing the performance of isolated or small-scale transportation facilities; however, they are limited in their ability to analyze network or system effects.
Traffic Signal Optimization Tools
Similar to the analytical/deterministic tools, traffic optimization tool methodologies are mostly based on the HCM procedures. However, traffic optimization tools are primarily designed to develop optimal signal phasings and timing plans for isolated signal intersections, arterial streets, or signal networks. This may include capacity calculations; cycle length; splits optimization, including left turns; and coordination/offset plans.
Macroscopic Simulation Models
Macroscopic simulation models are based on the deterministic relationships of the flow, speed, and density of the traffic stream. The simulation in a macroscopic model takes place on a section-by-section basis rather than by tracking individual vehicles. Macroscopic simulation models were originally developed to model traffic in distinct transportation subnetworks, such as freeways, corridors (including freeways and parallel arterials), surface-street grid networks, and rural highways.
Mesoscopic Simulation Models
Mesoscopic models combine the properties of both microscopic (discussed below) and macroscopic simulation models. As such, mesoscopic models provide less fidelity than microsimulation tools, but are superior to the typical planning analysis techniques.
Microscopic Simulation Models
Microscopic simulation models simulate the movement of individual vehicles based on car-following and lane-changing theories. These models are effective in evaluating heavily congested conditions, complex geometric configurations, and system-level impacts of proposed transportation improvements that are beyond the limitations of other tool types. However, these models are time consuming, costly, and can be difficult to calibrate.
A listing of the available Traffic Analysis Tools by category can be found in Appendix E of the Traffic Analysis Toolbox, Volume II: Decision Support Methodology for Selecting Traffic Analysis Tools.