This feature primarily serves as a penalty for reckless driving, and attempts to simulate a certain degree of realism in the game's vehicular accidents. The tendency for the player to be thrown out of vehicles varies among vehicle classes and models, hitting any NPC's vehicle at a high speed with a large vehicle may also result in their ejection.
Motorcycles and bicycles
In Grand Theft Auto 1, the player will be thrown forward from their motorcycle if they collide with vehicles past a certain speed. This feature offsets the motorcycles' superior maneuverability and nimble nature, and discourage recklessness.
GTA Vice City — GTA Chinatown Wars
Motorcycles were missing from Grand Theft Auto 2 and Grand Theft Auto III, but subsequently appeared in every GTA game from Grand Theft Auto: Vice City onwards, with the exception of Grand Theft Auto Advance; they continued to feature involuntary dismounts.
In GTA Vice City, more conditions for a dismount were added; in addition to impacts with vehicles and buildings, the player can also be thrown off when leaning the bike too far back during a wheelie, too far forward during a stoppie, or while the motorcycle is rolling backwards over a certain speed. This remained unchanged in GTA games which recycled GTA Vice City's game engine (GTA Liberty City Stories and GTA Vice City Stories). In Liberty City Stories, bonus points are awarded during the Karmageddon side mission for dismounting motorcycle drivers.
Bicycles, which debuted in GTA San Andreas, are particularly vulnerable — unlike motorcycles, hitting pedestrians full on with a bicycle will throw the player from the bike. Improved bike and cycling statistics improve the player's ability to hold onto a motorbike or bicycle during low-impact collisions, or while rolling backwards.
Grand Theft Auto IV continues to apply the same set of rules with regards to motorcycle dismounts, this time using ragdoll physics after players are thrown from their bike; this makes it difficult to predict the degree of injury the player may sustain. In GTA IV's single player, even a minor to moderate collision may propel the player off their bike; susceptibility to dismounts is adjusted, however, in GTA IV's DLC, The Lost and Damned. As the protagonist in TLAD is more accustomed to motorcycles than Niko Bellic, the risk of him being thrown off a bike is much lower. Multiplayer modes in all GTA IV-based games typically minimizes chances for player dismounts, in order to let the player focus more on the game and less on the driving.
Cars and aircraft
Involuntary ejections from a car or aircraft is a feature introduced later in the series, with Grand Theft Auto IV. If the player is travelling at a high speed and they smash into an object or vehicle (particularly an immobile one) head on, there is a chance they will be propelled through the windshield. If a player is ejected through the windshield, the windshield will shatter as the player is flung forward out of the vehicle, from which point GTA IV's physics engine sends the player's ragdoll rolling and bumping to a stop, inflicting damage with each impact. The feature also applies to the game's helicopters. It can be assumed that the protagonist may not wear a seat belt, at least on certain occasions, resulting in the tendency for him to be thrown out.
Although being ejected from the windshield is unlikely to kill a protagonist in decent health, the player may be thrown into oncoming traffic, risking collisions which will cause major damage. If a player is ejected straight into an oncoming vehicle (especially in places where traffic moves fast, such as a highway), the player risks being killed. Like dismounts in GTA IV, the effects of such an ejection can be catastrophic if the player is low on health. If the player is wearing a helmet on a motorcycle and they are ejected, impacts on the player's head will not cause damage.
If the player hits an NPC vehicle head-on at a high enough speed in a large enough vehicle then the player may kill the NPC from the crash, set the vehicle on fire (causing the NPC to exit the vehicle writhing in flames) or eject the NPC through the windshield of their vehicle. If the player causes fatal impact on the NPC, they will either slump back in their seat or land their head on the steering wheel causing the horn to go off for a few seconds (sometimes their foot will still be on the gas pedal thus the car will keep going until it hits something).
Although this would seem to add realism, and discourage to player to drive recklessly in cars, in reality you couldn't be ejected from the vehicle unless the car is tilted enough, no matter how hard the impact. In real life, the driver's torso and head would probably hit the steering wheel and the surrounding apparatus, and the feet and lower body are placed in an inset, which would prevent anybody from sliding out and breaking through the windshield. The airbag will usually inflate as well, lowering the chances of flying out even more. Perhaps this was added as there is no other way to take damage from collisions in a vehicle, unlike in real life (although this depends on the vehicle and collision, position of occupants etc.) where one may get injured or even killed in a collision.
- Bail out, a voluntary ejection from a vehicle.