"In contrast to previous GT titles, there's an increased emphasis on real world tracks, which include New York City, the Grand Canyon and the Tsukuba racing circuit. The reason for this has to do with GT4's highly sophisticated new physics engine. Here's the science part: each car's specifications (weight, size, engine format etc.) are input and from this data the team is given an accurate calculation of how that vehicle should perform, factoring in wind speed, friction and just about anything else you can think of. Hence, when driving around real world tracks, the lap times for each vehicle are utterly realistic."