Vehicle assembly for a vehicle , said vehicle assembly comprising: - a radar sensor configured to emit radar waves (R1), - an arrangement of layers comprising a primary layer , disposed facing said radar sensor and comprising an input surface (S1) for the radar waves (R1), a secondary layer comprising at least one relief , said secondary layer being adjacent to the primary layer and comprising a primary junction surface (Sj1) for the junction with said primary layer and a secondary junction surface (Sj2) for the junction with an adjacent tertiary layer , and said tertiary layer comprising an output surface (S3) for the radar waves (R1) parallel to said input surface (S1), the primary layer , the secondary layer , the tertiary layer respectively comprising a primary refractive index (n1), a secondary refractive index (n2), and a tertiary refractive index (n3), - the secondary refractive index (n2) and the tertiary refractive index (n3) being equal if the primary junction surface (Sj1) is parallel to the input surface (S1) and to the output surface (S3) and if the secondary layer has said relief on said secondary junction surface (Sj2), or the refractive indices (n1, n3) of the non-adjacent layers being equal if the secondary layer has a relief on said secondary junction surface (Sj2) and a relief on said primary junction surface (Sj1) and if the primary junction surface (Sj1) is parallel to the secondary junction surface (Sj2); characterized in that said input surface (S1) and said output surface (S3) are curved and have a radius of curvature Rm = γ*E(da)max, with E being the thickness of the arrangement of layers , (da)max being a tolerance for the error in the angular location of said radar sensor , γ being a factor depending on the largest angle of the field of view (FOV) of said radar sensor and on the tertiary refractive index (n3) of said tertiary layer . - a radar sensor configured to emit radar waves (R1), - an arrangement of layers comprising a primary layer , disposed facing said radar sensor and comprising an input surface (S1) for the radar waves (R1), a secondary layer comprising at least one relief , said secondary layer being adjacent to the primary layer and comprising a primary junction surface (Sj1) for the junction with said primary layer and a secondary junction surface (Sj2) for the junction with an adjacent tertiary layer , and said tertiary layer comprising an output surface (S3) for the radar waves (R1) parallel to said input surface (S1), the primary layer , the secondary layer , the tertiary layer respectively comprising a primary refractive index (n1), a secondary refractive index (n2), and a tertiary refractive index (n3), - the secondary refractive index (n2) and the tertiary refractive index (n3) being equal if the primary junction surface (Sj1) is parallel to the input surface (S1) and to the output surface (S3) and if the secondary layer has said relief on said secondary junction surface (Sj2), or the refractive indices (n1, n3) of the non-adjacent layers being equal if the secondary layer has a relief on said secondary junction surface (Sj2) and a relief on said primary junction surface (Sj1) and if the primary junction surface (Sj1) is parallel to the secondary junction surface (Sj2); <EOS>