Frontal crashes cause the majority of serious injury and fatalities on the roads. It is now accepted that one of the main goals in improving vehicle compatibility is to design vehicles to maximise structural interaction of vehicles with different geometry, mass and stiffness. A compatibility test procedure must be able to assess the shear connections of the vehicle front structure as well as provide for correct energy management between dissimilar crash partners so as to guarantee passenger compartment integrity, which is particularly important in the smaller vehicle. This paper details the research conducted by the Australian Department of Transport and Regional Services to examine the feasibility of a constant energy compatibility test using the Renault Progressive Deformable Barrier (PDB) [1]. This work has been provided to the IHRA Vehicle Compatibility Working Group to consider in its deliberations to develop a vehicle compatibility test.