In modern F1, race neutralization via Safety Car is done in two variations, the traditional SC Period, where the Safety Car actually goes out on track and collects the entire field to form a slow-running queue; and the new Virtual Safety Car where the drivers are simply required to run sector times that are over a specified Delta, effectively slowing them down as well.
From Formula 1 Official Website.
The VSC will primarily be used when double waved yellow flags are
needed on any section of the track, but the circumstances are not such
to warrant the safety car itself.
In the event of a more serious incident, particularly if competitors
or officials are in immediate physical danger, which is not severe
enough to warrant suspending the race but cannot be dealt with under
the VSC, then the safety car will be called.
(double waved yellow flags: Great danger. Slow down considerably. Be prepared to suddenly change from the projected racing line, or take other evasive action including stopping if necessary. No overtaking. (This signal may be supplemented or replaced by flashing yellow light(s), as an added warning). For more on flags.)