Colliding With Objects While Automatically Running Forward

I attached a script to a first person controller called Run_Forward so that the user automatically runs forward without pressing a button. However when I run into objects I go right through them or the objects are pushed out of the way. When I freeze every position and rotation on the object I just run through the object. Please help. My code is below.

using UnityEngine;
using System.Collections;

public class Run_Forward : MonoBehaviour {

// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {

	if (Input.GetKeyDown(KeyCode.A))
		transform.position += Vector3.right*4;
	
	if (Input.GetKeyDown(KeyCode.D))
		transform.position += Vector3.left*4;
	
	transform.Translate(0, 0, .2f);
	
}

}

transform.position ignores collision. You’d have to use rigidbodies, if you want collisions.