Summary: This paper contains results of accelerated pavement tests at elevated temperatures on dense graded asphalt concrete and gap-graded asphalt rubber hot mix. The APT testing was performed using a Caltrans Heavy vehicle Simulators. The overlays were placed on preciously untrafficked sections of an existing flexible pavement. Variables included in the experiment were overlay type, ARHM-GG overlay thickness, tire/wheel type, and pavement temperature. Results presented include the rut development for the different variables, changes in layer thickness, and changes in air-void content. Analyses were performed to evaluate the relative contributions of shear deformation and densification to rut development.