In Gran Turismo 4, the characteristics of the cars are realistically designed and calculated so that they handle to the "real-life" physics of that particular vehicle, taking into account weight, speed, friction, wind, and more. To further enhance the realism of the driving experience, new technology blends real-time action with a photo-fixed background to immerse the player in real-life environments such as New York City, the Grand Canyon and others. Highly detailed vehicles and environment mapping create broadcast-quality graphics, from light and competitor car reflections on the player's automobile to leaves on a tree shaking in the wind.
The online mode features a robust system for players to race with up to six other players and interact and chat with others to form an automotive community.
In offline gameplay, players will have the opportunity to race in an enhanced arcade and simulation mode based upon similar game mechanics from Gran Turismo 3 A-spec. In both modes, players will have access to experience more than 500 authentic automobiles encompassing manufacturers from around the world, with a range from vintage to modern vehicles. Courses include existing closed racing circuits to specially designed city courses, reaching a total count of up to 100 tracks.
The arcade mode allows players to compete against each other or the artificial intelligence on select courses. The simulation mode allows players to start from the bottom and earn their way up the ladder as they acquire driving licenses, race to earn money, unlock cars and courses, buy and sell cars, upgrade parts and compete in various championships. Playable from both first- and third-person perspectives, Gran Turismo 4 offers advanced opponent behavior to capture real-life racing and unpredictability of finishes.