It is always awkward when "safety" enters the discussion. Cutting to the chase, most of the time you can recognize a professional and truthful presentation of facts by the author's abstinence from the use of the S-word.
In a traditional case of damned if you do and exactly the same otherwise, any action's benefits have consequences on the negative side and weighing them against each other borderlines with the metaphysical. Sorting facts from chaff according to their relevance for any particular situation becomes impossible on purely technical grounds, without a "just cause" sense of direction.
In this respect, the only universal truth is that absolute safety can only be achieved once we simply stop flying. No airports, no machines, no humans.
As safety is of literal paramount importance what we use in the contemporary discourse (post-1985) is the terms "safety level" or "margin from error". That's the Columbus' egg: A change is to be reviewed relatively to what we already have, or against another possible choice. And this actually gives a good pivot point that even an informed outsider to the industry can use properly.
For your particular case:
1) For a given amount of movements at an airport, does a parallel dual runway configuration provide more room for error margins over
- a) a crossed double runway configuration
- b) a single runway configuration?
It is yes on both accounts. If you listed the genuine benefits of a parallel runway setup, the additional safety factor has a rightful place on it.
At the same time: If someone attempts to use "for better safety" call to justify building a secondary runway on top dubious capacity increase claims, they are destroying their credibility and blowing holes below own waterline.
Last edited by FlightDetent; 21st Dec 2020 at 08:03.