Atari today announced that the Test Drive Collection Volume 4 downloadable car pack is available now on Xbox Live Marketplace for Test Drive Unlimited. The Test Drive Collection Volume 4 features six highly desirable cars, the Dino 246 GT, Ferrari Challenge Stradale, Cadillac Cien, RUF RK Spyder, Lamborghini Murcielago Roadster, and the TVR T440R. In addition, players can download the Saturn Curve completely free. Once downloaded from Xbox Live Marketplace, players will be able to buy each of the cars as normal from the relevant in-game dealerships.