//Top of script:
new VehInfo[MAX_VEHICLES]=0;
//OnVehicleSpawn:
VehInfo[vehicleid] = 1;//Vehicle exists
//In a script to count vehicles:
new count=0;
for(new i = 0; i < MAX_VEHICLES; i++)
{
    if(VehInfo[i] == 1)
    {
        count++;
    }
}
printf("There are %d vehicles.",count);

new gStaticCars; // Global var

// GameModeInit
AddStaticVehicle(...);
AddStaticVehicle(...);
AddStaticVehicle(...);
gStaticCars = AddStaticVehicle(...); // This is to be the last vehicle that was created!

printf("There are %d cars.", gStaticCars);

new DynCars;
for(new v = 1; v < MAX_VEHICLES; ++v)
{
    if(!GetVehicleModel(v)) continue;
    DynCars++;
}