Dashes instead of underscores in url

[eluser]AntonioAntar[/eluser]
Hello friends

I'm using the latest version of codeigniter, I can't remember which one was it but I know it is the latest

there is an option in routes where you can change the underscores into dashes in the url, which I want to do for SEO purposes

I have the following in my routes.php

$route['translate_uri_dashes'] = TRUE;

Which does the job, as I can access all my url's using dashes

However, I can also access all my pages using underscores as well, so as it stands now all controllers can be accessed using underscores and dashes as my url

example: localhost/mainpage/test-page and localhost/mainpage/test_page both work

Is this the way it works? and which version will show up when I upload the website to the server? is there a way I can make the url's work only if they use dashes instead of underscores and not both?

Best regards