In this study, it is aimed to formulate a constitutive model accounting for the evolving features of the plastic anisotropy, in terms of both stresses and r-values, and the strain rate sensitivity during the plastic deformation. For the model calibration and validation, a bcc ferritic steel is selected. The material parameters are calibrated by tensile experiments under different loading configurations and different strain rates. Nakajima tests are conducted to characterise the cold formability of the selected steel. The model prediction is compared with the experimental results and it is concluded that the formability prediction is significantly improved when considering the evolving features during the plastic deformation.