Simplified methods are generally preferred in practice for the transverse bending analysis of concrete box-girder bridges. The cross-section of the bridge is generally modelled as a frame of unit width with imaginary supports at the web locations and simplified frame analysis (SFA) is carried out. Alternatively, a method (ISM) using influences surfaces for elastic plates (Homberg's or Pitcher's Charts), as recommended by AASHTO, is adopted for simplified analysis. Because of the various assumptions made in the modelling, the SFA and ISM results are found to be erroneous. While the ISM results are generally very conservative, the SFA results are found to be sometimes unconservative in some cases of vehicular leading. In an earlier investigation, the authors have studied and quantifed the nature of the errors in SFA with reference to detailed 3-dimensional finite element analyses (3DFEA), for box-girder bridges (single rectangular cell) without flange overhangs, and a set of correction factors proposed for use in design practice. In the present study, the procedure is extended to box-girder bridges with flange overhangs. Based on extensive numerical studies by both SFA and 3DFEA, a set of correction factors are proposed, and their use demonstrated through an illustrative example. It is established that the use of conventional SFA gives erroneous results which are eliminated by applying the proposed modifications.