Results of accelerated pavement tests (APT) at elevated temperatures on dense graded asphalt concrete and gap-graded asphalt rubber hot mix (ARHM-GG) are presented. APT testing was performed by use of a Caltrans heavy vehicle simulator. The overlays were placed on previously untrafficked sections of an existing flexible pavement. Variables included in the experiment were overlay type, ARHM-GG overlay thickness, tire/wheel type (dual/bias-ply; dual/radial, wide-base single, aircraft), and pavement temperature (40 deg C, 50 deg C, at 50 mm depth). Results presented include the rut development for the different variables, changes in layer thickness, and changes in air-void content. Analyses were performed for evaluating the relative contributions of shear deformation and densification to rut development.