Why ATC needs to emphasize "RNAV to fix" again during takeoff clearance?
 

I was watching the video below and at time 5:35 the tower says: They already have been cleared before. Why does ATC needs to repeat that again during takeoff. Any rules or ideas?

It turns out I'm not allowed to post a link for now. You can search for the video at youtube:
title: How to fly an IFR departure procedure with a climb via
poster: boldmethod

https://flightaware.com/resources/ai...SIX+(RNAV)/pdf

Just guessing here, could be that the other runways will be radar vectors to BOTLL? Just to specify that they're "on their own"? Or a normal part of the take-off clearance to state the turn after departure?

jmmoric yeah I was thinking that. I was wondering if there is a rule stating that ATC has to remind the departure just before takeoff at busy airports or is it just a personal technique of that specific ATC to make sure no one screws up.

Here's one reason.

It’s in the FAA AIM - “At some airports when a departure will fly an RNAV SID that begins at the runway, ATC may advise aircraft of the initial fix/waypoint on the RNAV route. The purpose of the advisory is to remind pilots to verify the correct procedure is programmed in the FMS before takeoff. “

At some airports ATC will ask you to verify the first waypoint in the your box before giving a take off clearance. They used to do it at Dublin (might still do) but as the first waypoint was common to two departures that turned in opposite directions I could never see the point.

Usually those rules comes when a crew makes a mistake.

Then a report is made.
Part of that report is always: "could we have done anything to avoid it".
From time to time it finds it's way into either local or general rules for the ATCO's.
Especially if the airlines comeback on their own mistake is: "you could at least....."

So we end up "babysitting" crews.

Yeah, I was thinking along those lines, but I was wondering if there are any rules specifically mandating that, other than ATC being prudent.

That makes sense it being an advisory, especially for busy airports where things can go wrong quickly. Because I haven't heard similar calls at most other airports.