Superpave asphalt mixtures have been used in highway pavements in the U.S. since the late 1990s. Modified binders have also been used in some of the Superpave mixtures in an effort to increase the cracking and rutting resistance of these mixtures. There is a need to evaluate the long-term performance of these mixtures and the benefits obtained from the use of modified binders, so that the Superpave technology and the selection of modified binders to be used could be effectively applied. A full-scale pavement-testing program was conducted to evaluate the rutting resistance of Superpave mixtures with and without polymer modification using a Heavy Vehicle Simulator (HVS). The HVS can apply realistic full-size wheel loads in an accelerated manner and can simulate 20 years of interstate traffic on a test pavement.