Pseudo equivalent widths of the Si IIλ6355 feature plotted against the velocity of the same line (v_Si) near maximum light (−5 to 5 days). Where several measurements exist for a given SN in the phase range used, we selected the one closest to maximum light. The different colours represent the different sub-types used in this study. The green filled and open circles represent respectively the NV SNe Ia and HV SNe Ia within the normal SNe Ia in our sample.