How to lerp a car while it's moving forward at a constant velocity

Questions & Answers
1

This car is a rigidbody2D object that is constantly going Vector3.up * 10 while it does not collide into anything on the 2D plane. While I can move the car left and right, it does not translate smoothly. My objective is to be able to move the car left and right smoothly, but the fact that the car is constantly moving and that I can’t just lerp the X-position of the car is causing me a headache.

void Update () {
		if (Input.GetKeyDown("left"))
		{
			if (transform.position.x > -1)
			{
				//Vector3 targetPos = transform.position;
				//targetPos.x -= 1.25f;
				MoveLeft ();
			}
		}
		if (Input.GetKeyDown("right"))
		{
			if (transform.position.x < 1.5)
			{
				MoveRight();
			}
		}
	}		                       

	void MoveLeft() {
		Vector3 targetPos = transform.position;
		targetPos.x -= 1.25f;
		transform.position = Vector3.Lerp(transform.position, targetPos, 1f);
	}
2

Use Mathf.Lerp rather than Vector3.Lerp to move just the X position of the car - then make your position a combination of the X you are lerping at the rest of it.

     float xPos = 0;
     float horizontalMovement = 2;

     void MoveLeft() {
         xPos = Mathf.Lerp(xPos, xPos-horizontalMovement, Time.deltaTime * 3);
     }

    void Update() {
        //Move vehicle upwards etc
        ...
        var pos = transform.position;
        pos.x = xPos;
        transform.position  = pos;
    }