Test Drive was one of the original games that had the concept of a free landscape. The user did not have to drive on a pre set course but go wherever they want. I.e. drive off the road and onto the grass, hills, farms and etc.
This concept was made famous in games such as the Grand Theft Auto series. Even small touches such as a car radio, windscreen wipers and headlights featured in this game. These are now predominant in games made today. The game shipped with three cars to drive; the Lamborghini Diablo, Ferrari Mythos Pininfarina Concept, and the Chevrolet Corvette CERV III Concept. An add on package was available as an extra purchase featuring additional road routes, and the Acura NSX and Dodge Stealth R/T Turbo.
Source: Wikipedia, "Test Drive III: The Passion", available under the CC-BY-SA License.