Abstract
This paper reviews the state-of-the-art measurement and formulation of link capacity functions or volume-delay curves, for use in traffic assignment procedures. The effect of the position of measuring vehicular flow and the length of sampling interval used is investigated qualitatively, and some practical recommendations are made. The "capacity" of a link is investigated, and it is concluded that capacity under "steady-state" conditions is the most appropriate measure. Some proposed link capacity functions are reviewed with respect to their proven ability to represent observed data, and their applicability in traffic assignment procedures.