The aim of this work was to investigate the phaseseparation effect in vitro for channels ,20 mm and for intermediate haematocrits, that is physiological conditions under which the effect is significant. For this purpose, we use RBC suspensions, microfluidic devices modelling microvascular bifurcations and new metrologies allowing the simultaneous quantification of both blood and RBC flow rates in the three branches of the bifurcation. First, these metrologies were validated by checking that their results are consistent with mass conservation of both blood and RBCs at microbifurcations. Second, the phase separation effect was studied, and the result compared with previous experimental and numerical results (Pries et al. 1989; Doyeux et al. 2011).