Accelerate and brake a car without wheel collider

I am trying to make a simple car game in Unity.
I want to make a car controller such that it can move forward and in X direction.

for moving car in X direction i am using
transform.translate.x
i can use the same for forward but i want it to accelerate its velocity relatively with time and to stop slightly on applying brake which is not possible in transform.translate.forward help me in doing this.

private Rigidbody rb;

void Start(){
   rb = GetComponent<Rigidbody>();
}

void Update(){
   if(Input.GetKeyDown(KeyCode.Space){
      rb.velocity *= 0.9f;  // it will slow down until it stops completly, if you multiply it by lets say 1.1f then it will accelerate
   }
}

If you want to have maximum speed you can change rb.velocity.magnitude and if it increases certein speed then you can stop accelerating etc.

why it’ll accelerate when u multiply by somthing bigger @mlnczk ,why it will accelerate when u multiply by 1.1f
@mlnczk

There’s also another solution to this. You can use Unitys lerp functions. When combined with time you can manipulate simple transforms such as transform translate. I do not have the code for this but search it up on google if you don’t want it to be physicsbased.