Traffic flow counter

Unity Engine
1

I want to see the traffic flow in an intersection, realtime, for 60seconds, but It doesn’t work.
This is my function:

private void Start()
        {
            _timer = 0;
            _nrOfCars = 0;
        }

        private void Update()
        {
           
            if ( _timer <60 )
                _timer += Time.deltaTime;
            else
            {
                Debug.Log(_nrOfCars + "   " + _timer );
                TrafficFlow = _nrOfCars / (_timer);
                _timer = 0;
                _nrOfCars = 0;
            }
        }
        /// <summary>
        /// Check if the car is near intersection
        /// </summary>
        /// <param name="other"></param>
        private void OnTriggerEnter(Collider other)
        {
           
            if (other.gameObject.tag == "Car")
            {
               _nrOfCars++;
                other.GetComponent<CarEngine>().Intersection = true;
             }
               
        }
2

When you say it doesn’t work, what are you expecting to happen that doesn’t, or, does happen that shouldn’t?