@Carolina 22:17 Apr 30, 2015
Both of the answers you've received so far have totally side-stepped the only potential problem in your source text: at-grade (which, I imagine, should in fact read: "AT-grade")*.
If I'm right about that, the appropriate/correct/best answer will depend on the country of origin of your source text - i.e. where this "AT" concept is defined/regulated.
With that in mind, which country (or rail-road system) is this talking about?
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* The Kudoz system is allergic to upper-case letters at the start of any term. | 
