Many facets of the transportation picture have not been coordinated into a single interdependent model even though the long-range planning efforts of transportation systems could benefit from such an effort. The many aspects of transportation-related problems make coordinated approaches important to a critical examination of these problems. Four major sectors of the transportation ecology require this coordination effort: the transportation system design sector, the economic sector, the environmental sector, and the energy supply sector. Currently there is a growing base of crises in each of these sectors of the transportation ecology. This paper puts forth a conceptual foundation for a general transportation ecology model (a model representing the functional environment of transportation systems). The empirical and theoretical considerations necessary for the foundations, as well as the expectations of the model concept, are explored.

In this paper a scheme is proposed for automating the scaling process for analog computers in hybrid (analog-digital) systems. The analog computer's magnitude and frequency constraints are imposed by a set of equations defining amplifier input factors. The digital computer is used not only to compute and implement these inputs but also to monitor analog amplifier outputs so that present scale factors can be revised when required. An example is included to illustrate the utility and function of the automation.

Abstract—Sensitivity functions which relate the effect of parameter variations to system variables may be calculated for linear systems by simultaneous integration of two sets of first-order linear differential equations. These sets have the same homogeneous part. This note describes how an analog computer may be used to solve these equations without using two distinct simulations wired together. The number of integrators in the analog simulation is equal to the system order.