A simple yet efficient traffic flow model, in particular one that describes vehicle longitudinal operational control and further characterizes traffic flow fundamental diagram, is always of great interest to many. Though many models have been proposed in the past, each with their own advantages, research in this area is far from conclusive. This paper contributes a new model, i.e., the longitudinal control model (LCM), to the arsenal with a unique set of properties. The model is suited for a variety of transportation applications, among which a concrete example is provided herein.