The difference is that as of today most public transport concepts have been tried and evaluated. None of them offered enough advantages to justify the cost of b

The difference is that as of today most public transport concepts have been tried and evaluated. None of them offered enough advantages to justify the cost of building a new network. Of course, it happens that new technology makes older concepts suddenly viable. But in public transport, the cost of the track is one of the major factors. The high cost for Maglev tracks killed the technology (yes, it may work in Japan where the geography leads to lines with insane capacity demands). Hyperloop will suffer from the same problem. The New York subway started with a revolutionary pneumatic railway and some other lines using standard gauge railway tracks. The pneumatic railway was quickly abandoned.