This paper jointly investigates non-linear attribute effects and discrete mixture heterogeneity. The research context relates to urban freight transport policy evaluation. The paper adopts an agent-specific perspective. The often unforeseen and undesired results deriving from urban freight transport policy implementation have induced many researchers to call for an in-depth analysis of specific agents’ preferences. However, the structural lack of appropriate data has hindered investigations at such a detailed level. This paper contributes to bridging this data and knowledge gap by: constructing an original dataset; testing for non-linear effects in attribute level variations; investigating the presence of inter and intra-agent heterogeneity;jointly exploring non-linear attribute effects and intra-agent heterogeneity.