This genre is mostly divided into two main groups, vehicular and specialty.
The variants of vehicular games appeared early, and the split stuck. They are differentiated by their camera perspective: the first-third person racing game and an overhead view.
The specialty racing games are mostly fad driven – they involve the hot racing style sport at the time.
One last subtype is the cart racing game, which simplifies the driving portion of the game and adds obstacles, strange trucks, and other action elements.
Common AI Elements
Where the road meets the rubber, track AI is the system needed to keep a CPU-controlled car on racetrack (or city street) at high speed within the rules of the game. This is usually a state-based system with the different vehicle states detailing the main ways that a racer can be on track. As guidelines, most games use combination of physical and optimal lines of travel (which are either data path laid down in track editor, or calculated automatically by a technique known as “finding the path of minimum curvature”, as shown in figure below) that mimic the invisible lines of travel that humans use when they race on tracks and roads.
Some games use traffic systems that look very realistic with lane changes, cars getting over for police vehicles, proper use of traffic lights and intersections. This is mostly FSM behaviors, with a lot of message passing to ensure that accidents don’t happen and some randomness to ensure that things don’t look repetitive.
A game like GTA 2 has different types of pedestrians for example, one type can stop by and steal your car, other one can pass away while you are moving. Other systems use simple flocking behavior.
Enemy and Combat
That’s about adding AI bots with weapons or something to play against the player.
NPCs are folks that you deal with to give you information, clean your car, etc… These characters are most probably scripted.
Other competitive behavior
Adding more interesting playing elements to the game, like having bridge fall down while you are racing with the car.
Useful AI Techniques
Finite State Machines (FSMs)
The traffic and pedestrians mostly use this technique to communicate and coordinate their movement.
A genetic algorithm is used to tune car performance parameters until it reaches best outcome to be used. Most probably that is done offline.
Areas that need improvement
Other areas of interest than crime
Not everybody’s mother wants to see her kid running over a prostitute for her wallet.
More intelligent AI enemies
it’d be great if the whole world simulations are computed together.