Learn Italian: Quanto tempo ci vuole per il tragitto? - How much time does the journey take?

Volerci is impersonal and describes how long an action takes in general. You use it when you don't mention a specific person. Metterci is personal and focuses on how long a specific person takes to do something. Since this asks how long the journey takes in general for anyone, we use ci vuole.

What is the subject of the verb ci vuole here?

With volerci, the subject of the sentence is actually the amount of time needed. Because Quanto tempo (How much time) is singular, we use the singular form vuole. If you asked about a plural amount of time, you would use the plural verb: Quante ore ci vogliono? (How many hours does it take?).

Does ci mean "there" or "us" in this sentence?

Neither! Here, ci is permanently attached to the verb to make the new verb volerci. Adding ci completely changes the meaning from volere (to want) to "to take" or "to be necessary" for time or effort.

Could I use viaggio instead of tragitto?

Yes, but they have a slightly different feel. Tragitto is usually used for a shorter route, commute, or the physical distance between point A and point B. Viaggio translates more broadly to "trip" or "journey" and often implies travel for vacation or a longer distance.