Learn Italian: Il transito va autorizzato dal direttore. - The transit must be authorized by the director.

This is the deontic passive (passivo di necessità). Using a simple tense of andare (like va) plus a past participle (like autorizzato) expresses a strong obligation. Va autorizzato means the exact same thing as deve essere autorizzato, but this andare structure is heavily preferred in Italian for formal rules, instructions, and official procedures.

If the subject were feminine, like la richiesta (the request), how would the verb change?

Because this is a passive construction, both the verb andare and the past participle must agree with the subject in gender and number. For a feminine singular subject, it would become La richiesta va autorizzata. If the subject were plural, it would be Le richieste vanno autorizzate.

Why is the word dal used here for "by the"?

In passive sentences, the person or thing actually performing the action (known as the agent) is always introduced by the preposition da (by). Because direttore is a masculine singular noun that takes the definite article il, the preposition da combines with il to form the articulated preposition dal.

Can I use this andare construction in a compound past tense, like the passato prossimo?