For larger simulations, visualization is nearly always an absolute necessity. Writing a visualizer, however, goes beyond the purposes of this text. One option is the Transims visualizer, on which the output formats in the following are based; since the whole Transims package is available to academic institutions for an affordable license fee, this may be an option. In some cases, visualizers of other transportation simulation software may be available. In this section it will be described how a graphics program that plots data points based on Cartesian coordinates can be used to generate some basic visualization. The public doman software ``gnuplot'' will be used. Other plotting packages with similar functionality should also work.