How to add player on road spawn script

Hiii. I am a beginner game developer with no coding experience. I am making a endless car game. I want add player by selecting them from menu. If I change car from menu the road spawn script won't work. Here's my script I used for road spawn : using UnityEngine; using System.Collections; using System.Collections.Generic;

public class RoadGenerator : MonoBehaviour {

 // road chunk prefab
 public GameObject roadChunk;

 // distance between edges of the chunk.
 public float chunkLength;

 // number of chunks to be activated at a time.
 public int drawingAmount = 3;

 // reference to player object. it is required to manage chunks on the scene.
 [SerializeField]private Transform player = null;

 // total number of chunks that actually exist in the scene
 [SerializeField]private int numberOfChunks = 7;

 // list of references to chunks in the scence
 private Queue<Transform> chunks;

 // reference to chunk that the player is on
 private Transform currentChunk;
 private int indexOfCurrentChunk;
 private int currentChunkPosition = 0;

 private void Awake()
 {
     InitializeChunksList();
 }

 private void InitializeChunksList()
 {
     chunks = new Queue<Transform>();
     for (int i = 0; i < numberOfChunks; i++)
     {
         GameObject _chunk = Instantiate<GameObject>(roadChunk);
         _chunk.transform.position = NextChunkPosition();
         if (i != 0)
             _chunk.SetActive(false);
         chunks.Enqueue(_chunk.transform);
     }
 }
  
 private void Start () {
     
 }
 
 private void FixedUpdate () {

     if (!player) return;

     // determine the chunk that the player is on
     currentChunk = GetCurrentChunk();
     indexOfCurrentChunk = GetIndexOfCurrentChunk();

     // Manage chunks based on current chunk that the player is on
     for (int i = indexOfCurrentChunk; i < (indexOfCurrentChunk+drawingAmount); i++)
     {
         i = Mathf.Clamp(i, 0, chunks.Count-1);
         GameObject _chunkGO = (chunks.ToArray()[i]).gameObject;
         if (!_chunkGO.activeInHierarchy)
             _chunkGO.SetActive(true);
     }

     if (indexOfCurrentChunk > 0)
     {
         float _distance = Vector3.Distance(player.position, (chunks.ToArray()[indexOfCurrentChunk - 1]).position);
         if(_distance > (chunkLength * .75f))
             SweepPreviousChunk();
     }

 }

 private void SweepPreviousChunk()
 {
     Transform _chunk = chunks.Dequeue();
     _chunk.gameObject.SetActive(false);
     _chunk.position = NextChunkPosition();
     chunks.Enqueue(_chunk);
 }

 private Vector3 NextChunkPosition()
 {
     float _position = currentChunkPosition;
     currentChunkPosition += (int)chunkLength;
     return new Vector3(0, 0, _position);
 } 

 private Transform GetCurrentChunk()
 {
     Transform current_chunk = null;
     foreach (Transform c in chunks)
     {
         if (Vector3.Distance(player.position, c.position) <= (chunkLength / 2))
         {
             current_chunk = c;
             break;
         }
     }
     return current_chunk;
 }

 private int GetIndexOfCurrentChunk()
 {
     int index = -1;
     for (int i = 0; i < chunks.Count; i++)
     {
         if ((chunks.ToArray()[i]).Equals(currentChunk))
         {
             index = i;
             break;
         }
     }
     return index;
 }

}

And sorry for my spelling..