我如何在Unity中根据速度调整转向角度

我正在观看这个(https://www.youtube.com/watch?v=kAEpLX3rfms)视频，了解如何在Unity中制作汽车。但我的车并没有根据视频的速度降低方向盘的角度。这个想法是你可以在最慢的时候把车开到50度，最快的时候开到10度。但这对汽车没有影响。谁能告诉我怎么修这个?

代码:

public WheelCollider wheelFL;
public WheelCollider wheelFR;
public WheelCollider wheelRL;
public WheelCollider wheelRR;
public Transform wheelFL_Trans;
public Transform wheelFR_Trans;
public Transform wheelRL_Trans;
public Transform wheelRR_Trans;
public float lowSpeedSteerAngle;
public float highSpeedSteerAngle;
public float Torque;
public float centerOfMassHeight;
public float speed;
public GameObject speedometer;
public GameObject accelerator;
public GameObject brake;
public float pedalRotationFactor;
public float speedometerRotationFactor;
public float decelerationRate;
public float currentSpeed;
public float topSpeed;
public float maxReverseSpeed;
public GameObject trunk;
public Material[] brakeMaterials;
public float currentSteerAngle;
public float turnAmount;
private Vector3 com;
private Rigidbody rigidBody;
private float acceleratorSpeed;
private float brakeSpeed;
void Start () {
    rigidBody = GetComponent<Rigidbody>();
    com = rigidBody.centerOfMass;
    com.y = centerOfMassHeight;
    rigidBody.centerOfMass = com;
}
void FixedUpdate () {
    currentSpeed = 2 * Mathf.PI * wheelFL.radius * wheelFL.rpm * 60 / 1000;
    if(currentSpeed < topSpeed && currentSpeed > -maxReverseSpeed){
        wheelFL.motorTorque = Torque * Input.GetAxis("Vertical");
        wheelFR.motorTorque = Torque * Input.GetAxis("Vertical");
        wheelRL.motorTorque = Torque * Input.GetAxis("Vertical");
        wheelRR.motorTorque = Torque * Input.GetAxis("Vertical");
    }else{
        wheelFL.motorTorque = 0;
        wheelFR.motorTorque = 0;
        wheelRL.motorTorque = 0;
        wheelRR.motorTorque = 0;
    }

    if(!Input.GetButton("Vertical")){
        wheelFL.brakeTorque = decelerationRate;
        wheelFR.brakeTorque = decelerationRate;
        wheelRL.brakeTorque = decelerationRate;
        wheelRR.brakeTorque = decelerationRate;
    }else{
        wheelFL.brakeTorque = 0;
        wheelFR.brakeTorque = 0;
        wheelRL.brakeTorque = 0;
        wheelRR.brakeTorque = 0;
    }
    if(Input.GetAxis("Vertical") < 0){
        //Changing The Materials
        Material[] mats = trunk.GetComponent<Renderer>().materials;
        mats[0] = brakeMaterials[1];
        trunk.GetComponent<Renderer>().materials = mats;
    }else{
        //Reseting The Materials
        Material[] mats = trunk.GetComponent<Renderer>().materials;
        mats[0] = brakeMaterials[0];
        trunk.GetComponent<Renderer>().materials = mats;
    }
    speed = GetComponent<Rigidbody>().velocity.magnitude * 15;
    float speedFactor = 1 - (GetComponent<Rigidbody>().velocity.magnitude * 3.6f / topSpeed);
    currentSteerAngle = highSpeedSteerAngle + ((lowSpeedSteerAngle - highSpeedSteerAngle) * speedFactor);
    turnAmount = currentSteerAngle * Input.GetAxis("Horizontal");
    wheelFL.steerAngle = turnAmount;
    wheelFR.steerAngle = turnAmount;
}
void Update () {
    wheelFL_Trans.Rotate(0, 0, wheelFL.rpm / 60 * 360 * Time.deltaTime);
    wheelFR_Trans.Rotate(0, 0, wheelFR.rpm / 60 * 360 * Time.deltaTime);
    wheelRL_Trans.Rotate(0, 0, wheelRL.rpm / 60 * 360 * Time.deltaTime);
    wheelRR_Trans.Rotate(0, 0, wheelRR.rpm / 60 * 360 * Time.deltaTime);
    Vector3 wheelSteerAngle = wheelFL_Trans.localEulerAngles;
    wheelSteerAngle.y = turnAmount + 90;
    wheelFL_Trans.localEulerAngles = wheelSteerAngle;
    wheelFR_Trans.localEulerAngles = wheelSteerAngle;
    if(Input.GetKeyDown(KeyCode.P)){
        Vector3 resetPosition = new Vector3(transform.position.x, 1.5f, transform.position.z);
        Quaternion resetRotation = Quaternion.Euler(0f, 0f, 0f);
        //Reseting Velocity
        GetComponent<Rigidbody>().velocity = new Vector3(0f, 0f, 0f);
        //Reseting Rotation
        transform.rotation = resetRotation;
        //Reseting Position
        transform.position = resetPosition;
        //Reseting Motor Torque and Steering Angle
        wheelFL.motorTorque = 0f;
        wheelFR.motorTorque = 0f;
        wheelRL.motorTorque = 0f;
        wheelRR.motorTorque = 0f;
        wheelFL.steerAngle = 0f;
        wheelFR.steerAngle = 0f;
        wheelRL.steerAngle = 0f;
        wheelRR.steerAngle = 0f;
    }
    acceleratorSpeed = wheelFL.motorTorque;
    brakeSpeed = wheelFL.motorTorque;
    if(acceleratorSpeed < 0){
        acceleratorSpeed = 0;
    }
    if(brakeSpeed > 0){
        brakeSpeed = 0;
    }
    if(speed >= 350){
        speed = 350;
    }
    speedometer.transform.localRotation = Quaternion.Euler(speed * speedometerRotationFactor - 100, 90f, 0f);
    accelerator.transform.localRotation = Quaternion.Euler(acceleratorSpeed * pedalRotationFactor, 0f, 0f);
    brake.transform.localRotation = Quaternion.Euler(brakeSpeed * pedalRotationFactor * -1, 0f, 0f);
}

float speedFactor = GetComponent<Rigidbody>().velocity.magnitude * 3.6f / maxSpeed; //or magnitude * 2.236936f for miles/h

public float lowSpeedSteerAngle;
public float highSpeedSteerAngle;