How to measure forward velocity - InverseTransformDirection not working ?!

I'm making a simple car driving game.

I'm trying to display forward velocity on screen.

...But both rigidbody.velocity.z and transform.InverseTransformDirection(rigidbody.velocity).z return the same value. They both go negative when I turn the car around.

What am I doing wrong?

Thanks in advance!

 public class UIManager : MonoBehaviour
 {
     public GameObject car;
 
     Rigidbody carRb;
 
     public Text stats;
     public Text stats1;
 
     private void Start()
     {
         carRb = car.GetComponent<Rigidbody>();
     }
 
     private void Update()
     {
         Vector3 worldVelocity = carRb.velocity; 
         Vector3 localVelocity = transform.InverseTransformDirection(carRb.velocity);
         stats.text = "World Velocity Z: " + Mathf.Round(worldVelocity.z * 36)/10 + " Km/h";
         stats1.text = "Local Velocity Z: " + Mathf.Round(localVelocity.z * 36)/10 + " Km/h";
     }
 }