The aim of this paper is to improve and complete the results presented in a previous work published on this journal about an experimental campaign focused on the hydraulic efficiency of continuous transverse grates for draining paved areas. This type of surface drainage structure is commonly used in urban or impervious areas (public squares, airport pavements, parks, and pedestrian areas), where conventional inlets are not recommended because they are rendered ineffective by the lack of a well-defined channelized flow path and gradients capable of directing flows toward the collecting hydraulic structures. In this paper, a methodology is presented to estimate the hydraulic efficiency of nontested continuous transverse grates. Empirical expressions are proposed to relate grate hydraulic performance to flow parameters and grate geometry without the need for laboratory tests. Moreover, the spectrum of the grates was extended in terms of dimensions and hydraulic design with respect to the first study, to enlarge the range of validity of the proposed empirical expressions.