Critical research needs associated with the effective application of visualization to transportation systems projects are identified. Visualization research needs are discussed within a broader, multidisciplinary context of technology development in the areas of simulation and modeling. Parallels are drawn between the current state of the practice in transportation as compared with that in the military-defense and aerospace areas. Some major differences between those areas and transportation systems development and user environments are noted, in particular (a) the current absence within the transportation community of a strong government research and development focal point for visual simulation and modeling and (b) the absence of an economic imperative similar to what prompted the defense community to embrace fully these technologies (i.e., fuel shortages, training system costs, and force readiness).