The flow of pedestrians through public spaces and thoroughfares is frequently a concern of architects, engineers, and planners, as well as building owners and operation managers, who may want to identify potential traffic bottlenecks, reduce congestion, and improve safety. Commercially available pedestrian software models have become highly useful tools for those purposes: They can simulate and graphically present the movement of individuals, small groups of people, and large crowds for analysis. Simulation models do not provide specific answers to pedestrian traffic problems. Instead, they allow users to test various scenarios to see what approaches might work best. For example, a transportation engineer designing a train platform might run simulations for stairway placement to optimize pedestrian clearance times. See also: Architectural engineering; Computer-aided engineering; Computer graphics; Model theory; Railway engineering; Simulation; Software; Transportation engineering

For pedestrian traffic models to work effectively, they must be calibrated against the actual movements of individuals and crowds. Pedestrian walking speeds depend on the type of facility, corridor widths, time of day, baggage carried, cellphone use, crowd density, and other factors. Often, this real-world data can be captured as video recordings and then put into a model to develop algorithms that accurately allow simulated agents (as proxies for people) to move autonomously and interact with the designed environment. Most models allow the simulation of as many agents as needed and for programming individual or group properties. As a result, even large events, such as major city marathons with 40,000 runners and a million spectators, can be simulated. See also: Algorithm; Artificial intelligence

Other simulations of pedestrian behavior include planning for the evacuation of high-rise buildings, special events, or cities; comparing designs for buildings, airports, sports arenas, and other facilities; assessing the effects of major delays at commuter train stations and other transportation hubs; and planning for the effects of population growth on urban sidewalks, crosswalks, and subway platforms. See also: Air transportation; Airport engineering; Buildings; Civil engineering; Facilities planning and design; Fire safety (building design); Subway engineering