And I agree re: the building entrance issue and later choke points. Anyone recall the time several years ago that most of the Valley was isolated? One route was across the ?Bay? Bridge; it was down for planned maintenance when backhoe fade struck around San Jose. How many paths is enough?
In my opinion, the following rule of thumb is reasonable. 1 path is enough for a site/enterprise that shuts down its services evenings and weekends. 2 paths is enough for a site/enterprise that provides a 24 hour, 7 day per week service. 3 paths is enough for a population center with under a million inhabitants. 5 paths is enough for a population center with over a million inhabitants. And a very few population centers such as New York, London, Tokyo, and Cheyenne Mountain should probably have more than 5 paths. --Michael Dillon