Traffic

Traffic refers generally to the other vehicles you encounter in free ride.

Dopplers and Mavericks

AddHubTrafficVehicle

The AddHubTrafficVehicle command adds a Doppler Truck or Maverick (Bonus Car) to a zone. The arguments specify the name of the hub, the type of traffic (Radar_VistaPoint, Radar_VehicleLivery, Radar_Challenge, or Vehicle), the internal name of the vehicle, a bounding box for the path to follow, and the name of the race that unlocks the traffic on the map. The axis-aligned bounding box is given as min and max coordinates, x0 x1 z0 z1. It seems like the traffic follows a random closed loop within the bounding box counterclockwise. The command is used in GameTsc/Story/hubinfos.tsc.

Doppler Trucks

When the traffic type is one of the Radar_* types, it's a Doppler. The vehicle internal name argument is always MESH_ID_TRAFFIC_TRUCK, which has the human-readable English name "Test" and appears as a Test Vehicle. It looks like a white Bonesaw (MESH_ID_TRUCK_ALL_1), but it is a distinct vehicle. Obviously, if you crash into the Doppler, it unlocks the class of thing that it is for on the map.

Mavericks

When the traffic type is Vehicle, it's a Maverick. The vehicle def for a Maverick will have a line like AddVehicleUnlock MESH_ID_BONUS_ROAD_3 -1 "NONE" "NONE". Obviously, if you crash into the Maverick, it unlocks that vehicle for you.

Fleet Vehicles

These are the black trucks and jeeps that drive around everywhere. They seem to spawn on random road points near the player and drive to a random target nearby before despawning.

TrafficON/TrafficOFF

Confusingly, the TrafficON/TrafficOFF commands only turn on and off the fleet vehicles and not all traffic. Dopplers and Mavericks will still be around when you run TrafficOFF. It makes sense why, but the command name contradicts the other command, which calls those vehicles traffic.

Vehicle Selection Behavior

The vehicle internal name that is used is selected in 005C3D70. Specifically, a random number between 0 and 1 is generated at 005C3E79, then with a 50/50 probability, either MESH_ID_FLOTTE_BIGTRUCK_1 or MESH_ID_FLOTTE_JEEP_1 is selected as the vehicle. These strings are hardcoded in the executable. It is possible to set any vehicle name there, so custom code could be overwritten to add more vehicles with a different probability distribution. The random number comes from GenWorld_Z's random number generator and incorporates the vehicle's position into the seed. That random number generator probably deserves its own page, but for now: 00640700, 0074E600.