Vissim is a tool used to evaluate uninterrupted and interrupted facilities. Vissim inputs need a more granular level of detail than macroscopic or mesoscopic models. Vissim is a microsimulation modeling program that simulates the movements of individual vehicles throughout a predefined network. A sketchlevel or macroscopic modeling tool aggregates vehicle behaviors between decision points. Vissim, by contrast, tracks every movement that every vehicle makes from the moment it enters the network until the moment it exits the network.

Vissim inputs include volume, roadway, and signal timing parameters. Vissim outputs include traffic and environmental MOEs. Vissim accounts for randomness and factors not included in the HCM calculations, including driver behavior and how delays in one part of the network impact every other part of the network. This makes Vissim more accurate, particularly when evaluating oversaturated conditions. Vissim reports simulation output by location. Vissim simulations can be exported as video files to demonstrate the conditions to expect in the field. Vissim is typically used to analyze complicated or unusual geometry, oversaturated conditions, alternative intersections, and complex urban facilities/networks.

Vissim (or an alternative microsimulation tool) is often used to analyze locations with the following characteristics: