Car physics 2d top down - unity 5

using UnityEngine;
using System.Collections;

public class car : MonoBehaviour {

    private float speed = 0f;
    private float maxSpeed = 15f;
    private float startAngluraDrag;
    private float startOrthoSize;


    void Start () {
        startOrthoSize = Camera.main.orthographicSize;
        startAngluraDrag = GetComponent<Rigidbody2D> ().angularDrag;
    }

    void FixedUpdate () {
        CameraFunctions ();
        InputHandlingKB ();
        MovementHandlersRigid ();
    }

    //using rigidbody2d
    private void MovementHandlersRigid() {
        GetComponent<Rigidbody2D> ().AddForce (transform.right * speed);
        if (GetComponent<Rigidbody2D> ().velocity.magnitude > 0.5f) {
            GetComponent<Rigidbody2D> ().angularDrag = startAngluraDrag;
            GetComponent<Rigidbody2D> ().AddTorque (-Input.GetAxisRaw ("Horizontal"));
        } else {
            GetComponent<Rigidbody2D> ().angularDrag = 10f;
        }
    }

    //keyboard && gamepad
    private void InputHandlingKB() {
        if (Input.GetKey (KeyCode.UpArrow) || Input.GetAxisRaw ("Fire2") > 0f) {
            if (speed < maxSpeed) {
                speed += 0.1f;
            }
        } else if (Input.GetKey (KeyCode.DownArrow) || Input.GetAxisRaw ("Fire3") > 0f) {
            if (speed > 0f) {
                speed -= 0.3f;
            }
        } else {
            if (speed > 0f) {
                speed -= 0.2f;
            }
        }
        if (speed < 0f) {
            speed = 0f;
        }
    }

    //camera follow, smooth
    private void CameraFunctions() {
        if (speed > startOrthoSize) {
            Camera.main.orthographicSize = Mathf.Lerp (Camera.main.orthographicSize, 5f, Time.deltaTime * 0.5f);
        } else {
            Camera.main.orthographicSize = Mathf.Lerp (Camera.main.orthographicSize, startOrthoSize, Time.deltaTime * 0.5f);
        }
        Camera.main.transform.position -= (Camera.main.transform.position - new Vector3(transform.position.x, transform.position.y, -10f)) * Time.deltaTime * 10f;
    }
}