Policy-making on Urban Freight Transport (UFT) is complex because it requires dealing with heterogeneous stakeholders with different objectives. The often unforeseen and undesired results deriving from UFT policy implementation have induced many researchers to call for an in-depth analysis of specific stakeholders' preferences. However, the structural lack of appropriate data has hindered investigations at such a detailed level. This paper explores the acquisition of stated preference data and calculation of Willingness To Pay (WTP) measures for a rigorous ex-ante policy analysis. Discrete choice models are estimated taking into account both nonlinear attribute effects and within stakeholder type heterogeneity. The results show that different WTP measures apply for given policy changes, and they suggest that policy makers should envisage differentiated reactions to the implementation of an urban freight policy change.