As a basic characteristic of traffic flow, vehicular travel speed is indispensable in many research and management tasks. In travel speed estimation, vehicular free-flow speed is a crucial determining factor, particularly when the traffic is light or moderate. The current state-of-the-art modeling of free-flow speeds is explored. The development of models of free-flow speed for Indiana arterial roads that may also be suitable for other states in the Midwest is described. Separate free-flow-speed models are presented for cars and trucks during daytime and nighttime hours. Aggregate models could easily be available if the methods provided are followed. The presentation includes the research background, the data-collection and data-processing procedures, a description of model development, and an analysis and a description of a means of refinement of the model.