Increase forward speed

I have an object that I want to give a forward speed when the game starts. The forward speed needs to increase every 5 seconds. I tried everything, but no joy.

var speed           : float = 5.0;
var increaseAmount  : int = 5;

InvokeRepeating("IncreaseSpeed", 2, 2);

function IncreaseSpeed ()

{
speed += increaseAmount;
}

function Update ()

{
    transform.Translate(Vector3.forward * Time.deltaTime);
}

This is the script I found, but it’s not working. Someone who can help me please?

Thanks in advance

Just replace Rotate with Translate, for instance:

function Update(){
    transform.Translate(Vector3.forward * speed * Time.deltaTime);
}

well i did same thing just with buttons for example w increases object speed and s decrease it

`

    public Transform mover;
public float maxSpeed = 0.1f;
public float curentSpeed = 0f;

// Use this for initialization
void Start () 
{

}

// Update is called once per frame
void Update () 
{
	if(Input.GetKey(KeyCode.W))
	{
		adjustCurentSpeed(+0.001f);
	}
	
	if(Input.GetKey(KeyCode.S))
	{
		adjustCurentSpeed(-0.001f);
	}
	
	mover.transform.Translate(0, 0, curentSpeed);
}

public void adjustCurentSpeed(float adj)
{
	curentSpeed += adj;
	
	if(curentSpeed <=0f)
	{
		curentSpeed = 0f; // if speed goes below 1 it stays 0, doesnt go negative
	}
	
	if (curentSpeed > maxSpeed)
	{
		curentSpeed = maxSpeed; // curent speed never goes over max speed
	}
	
	if (maxSpeed < 0.1f)
	{
		maxSpeed = 0.1f;
	}
}

`

you can just edit it to auto increase it over time without key input, hope it helps.