Setting up permissions
I think you should try something like this 

function mymodule_menu() {
  $items['example/car/%'] = array(
    'title' =&gt; 'Example RSS feed', 
    'page callback' =&gt; 'example_feed', 
    'access arguments' =&gt; 'mymodule_abc_view', 
    'type' =&gt; MENU_CALLBACK,
    );
    return $items;
}

function mymodule_abc_view() {
    return 'TRUE after checking something';
}


your URL should pass the car id or something to check the permission.