local empty = {
	 [0] = nil,
	 [1] = nil,
	 [3] = nil
}

local driver = {
	 [0] = "I'm the driver",
	 [1] = nil,
	 [3] = nil
}

local passenger = {
	 [0] = nil,
	 [1] = nil,
	 [3] = "I'm a passenger"
}

print( next(empty) )
print( next(driver) )
print( next(passenger) )