Disgrace, on 08 Jul 2017 - 10:35, said:
Even if there are red flags, it doesn't seem appropriate to have vehicles crossing the circuit while cars are still out there.
There will be cases where vehicles need to be at the site of an accident to provide immediate support for the driver in trouble.
If you lower the bar for yellow flags to, for example, debris on the track you - as race director and clerk of the course - lose a valuable tool and are left with only a safety car or red flag.
The FIA International Sporting Code is very clear about the meaning of the flags:
Quote
7.2.4 Signalling
Double waved yellow: Reduce your speed and be prepared to change direction or stop. There is a hazard wholly or partly blocking the track.
Red flag: Drivers must stop where they are and await instructions from the marshals.
Whether or not the flags were used properly and in such places as would have alerted the drivers to the actions of the marshals is worth investigating as well, because from the video posted it looks very much like people weren't exactly being eager to inform the drivers.