Due to economic and land use constraints, the low-volume roads tend to be narrow and with steep side-slope angles, resulting in traffic loads applied close to the pavement edge and in compromised confinement of unbound granular layers (UGLs). Field evidence suggests that both edge loads and steep side slopes accelerate pavement deterioration, but the mechanics remain unclear. This paper presents a computational approach to evaluate the impact of load position and side-slope angle on pavement deterioration. A 3D finite element (FE) model of low-volume pavement is developed, incorporating novel material models to account for stress-dependent behaviour and permanent deformation in unbound layers, along with a method to evaluate the impact of side-slope material on road performance. The numerical results concerning reduced bearing capacity and accelerated deterioration due to increased slope angles and edge-proximal loads are in agreement with field and full-scale test data. Thus, the proposed approach serves as a viable tool to quantify the impact of shoulder width and side slope on pavement performance.