Unity2D Check which direction the enemy AI is heading?

Hey I need assistance figuring out which way my AI is going so I can rotate the vehicle if needed.

I tired to us xDir and yDir. The xDir script works great but the yDir script is funky and making the vehicle rotate when going in the x direction.

Here is my code:

 using UnityEngine;
 using System.Collections;
 
 public class AICarScript : MonoBehaviour {
 public Transform[] waypoints;
 int cur = 0;
 
 public float speed = 0.3f;
 
     // Use this for initialization
     void Start () {
     
     }
     void CheckDirection()
     {
     //Declare x and y movement variables. Ranges from -1 to 1
     int xDir = 0;
     int yDir = 0;
     yDir = waypoints[cur].position.y > transform.position.y ? 1 : -1;
     xDir = waypoints[cur].position.x > transform.position.x ? 1 : -1;
 
         //Check if the car is going left or right
             if (xDir == 1)
             {
             GetComponent<SpriteRenderer>().flipX = true;
             //GetComponent<Rigidbody2D>().rotation = 0;
 
 
             }
             else if (xDir == -1)
             {
             GetComponent<SpriteRenderer>().flipX = false;
             //GetComponent<Rigidbody2D>().rotation = 0;
 
             }
 
         //Check if the car is going up and down
         if (yDir == 1)
         {
         GetComponent<Rigidbody2D>().rotation = 90;
         }
         else if (yDir == -1)
         {
         GetComponent<Rigidbody2D>().rotation = -90;
         }
         else if (yDir == 0)
         {
         GetComponent<Rigidbody2D>().rotation = 0;
         }
 
 
     }
     // Update is called once per frame
     void Update () {
 
     //Waypoint not reached yet? Move towards it
     if (transform.position != waypoints[cur].position)
     {
     Vector2 p = Vector2.MoveTowards(transform.position, waypoints[cur].position, speed);
     GetComponent<Rigidbody2D>().MovePosition(p);
     CheckDirection();
 
     }
     ///Waypoint reached
     else cur = (cur + 1) % waypoints.Length;
 
     }
     bool valid(Vector2 dir)
     {
     Vector2 pos = transform.position;
     RaycastHit2D hit = Physics2D.Linecast(pos + dir, pos);
     return (hit.collider == GetComponent<Collider2D>());
     }
 
 
 
 }