In preparation for the meeting today, I talked to my colleagues who are economists and asked them the same question. They said that the research has not identified a magic distance. In other words, they have been unable to determine whether demand would be lower with a longer distance or higher with a shorter distance. It is a continuum. Later on, we can provide the committee the details on how we arrived at this figure. In general, we found that this distance was optimal for access to rail lines.
On September 20th, 2016. See this statement in context.