Gameplay
Players now accumulate points by winning races in the normal first-person driving mode, called A-Spec mode. Each race event can yield up to a maximum of 200 A-Spec points. Generally, a win using a car with less of an advantage over the AI opponents is worth more points. Points can only be won once, so to win further points from a previously-won event, it must be re-won using a car with less of an advantage over the AI. There are also the 34 Missions which can yield 250 points each. Despite this, A-Spec points are experience points, not money.
The new B-Spec mode puts players in the place of a racing crew chief: telling the driver how aggressively to drive, when to pass, and mandating pit stops (by monitoring tire wear and fuel level). The speed of the time in the race can be increased up to 3x, allowing for Endurance races to be completed in less time than would take in A-Spec mode. The 3x feature, however, must be turned on after every pit stop because it resets to normal time. The game manual says that the player may speed up B-Spec mode by up to 5x, but this is believed to be a typo. B-Spec points are given out for each race completed in B-Spec mode. This increases the skill level of the AI driver in the categories of vehicle skill, course skill, and battle skill. Players can thereby use B-Spec mode in harder races as the game progresses, but this mode cannot be used on wet, dirt and snow courses.
Another new addition to the game is the Driving Missions, which are similar in experience to the license tests, but award successful completion with 250 A-Spec points and 1000 of more credits. Each mission takes place with a given car on a given track or section of track, and a given set of opponents. There are 4 sets of missions: The Pass, in which the driver must overtake an opponent within a certain distance; 3 Lap Battle, in which the driver must pass 5 opponents over the course of 3 laps; Slipstream Battle, in which the driver must overtake identical opponents by way of drafting; and 1 Lap Magic, in which the driver starts with a significant time penalty against much slower opponents and must overtake them all in the space of a single lap. Completing each set of missions earns the player a prize car. There are a total of 5 prize cars available to be won, they are DMCDelorean, Jay Leno Tank Car, Pagani Zonda Race Car, Toyota 7, and the Nissan R89C.
A new Photo Mode is included in the game, which allows the player to control a virtual camera, taking pictures of their cars on the track or at specific locations, including the Grand Canyon. This game is able to produce a selection of screenshots with variable compression rate (Normal/Fine/SuperFine) and size (up to 1280x960 72dpi), and the user can choose to save or print to a supported USB device.
Compared with Gran Turismo 3, graphics are greatly improved (despite running on the same PlayStation 2 hardware). The physics is also greatly improved, with the major upgrade that cars now experience body movement (such as dive under brakes). Barriers have a lot more friction to slow down the cars in GT3 (in an attempt to stop the use of "wall riding"), however there is minimal friction between cars, so the advantage obtained by running into the side of another car (instead of braking) is still present.
Read more about this topic: Gran Turismo 4