Rigidbody is getting stuck on my road

I am building a procedurally generated road, but my cube/car is still just stopping on random occasions. The road is made out of repeating one 5/5/1 cube.

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Drive : MonoBehaviour
6. {
7.     public float speed;
8.     public float torque;
9.     public float maxVelocity;
10.    
11.     void FixedUpdate () {
12.         if (Time.time > 2.5) {
13.             float moveHorizontal = Input.GetAxis ("Horizontal");
14.             GetComponent<Rigidbody>().AddForce(transform.forward * speed * Time.deltaTime);
15.             transform.rotation *= Quaternion.Euler(transform.up * moveHorizontal * torque * Time.deltaTime);
16.         }
17.  
18.         if (GetComponent<Rigidbody>().velocity.z > maxVelocity) {
19.             GetComponent<Rigidbody>().velocity -= new Vector3(0, 0, GetComponent<Rigidbody>().velocity.z-maxVelocity);
20.         }
21.     }
22. }
23.