Observed vs. calculated relative transit durations for the 15 systems presented in this paper, together with the 30 HATNet and 30 WASP planetary systems detailed in Appendix B. Equation (16) was used to derive Q_tran(calc). The surplus of objects above the 45° line indicates the expected effect of off-central transit. The slight excess of systems below the 45° line is due to errors in the stellar masses and radii.