System Upgrades: The BorderTransportationSystem will be around for dozens of decades and therefore, the surrounding world's technology will be upgraded and advanced a multitude of times over.  One hopes that the technology used at the time of the build will be the latest available, and that the manufacturers of the components will remain in business, and be adding reliability and features each decade. One of the faults in any technical system is that one tends to jump issued variations, i.e., go from version A to version D without ever going to version B and C.  This 'jump' can result in the system becoming totally obsolete as a jump from version A to say D may result in total failure of all the other components that are dependent on versions A B C.  Components of any complex system are usually connected to components from other systems or manufacturers, therefore it will be imperative that whenever a modification or upgrade is available, all the attached component manufacturers be notified so that the consequences be analyzed and problems prevented or resolved in advance of the actual installation. Index of ...