Aerial navigation: Maybe the failure mode was missing the floor on balloon size? If unobtainium balloons that size existed, then yes, Model T blimp. Outboard

Aerial navigation: Maybe the failure mode was missing the floor on balloon size? If unobtainium balloons that size existed, then yes, Model T blimp. Outboard fishing blimp. Wind/weather becomes an airplane-sized issue. Perhaps they over-extrapolated from shrinking sizes (lighter construction, hotter air and hydrogen) to 'becomes boat-like'? City Improvements up to date: Hmm. Cities had a lot more open space. And to build a building, you put in a rail line to the site. Now moving even a small woodframe, requires taking down poles and avoiding bridges[1]. IC and steelframe made construction cheaper. But, http://www.searsarchives.com/homes/1908-1914.htm http://www.searsarchives.com/homes/1908-1914.htm . And current manufactured and modular homes. So it works for small buildings. The pictured block-size construction seems implausible for stress scaling. Economics didn't work for new large buildings? And no room to slide away old large buildings? Shopping made easy: Maintenance nightmare, especially outside. Boston subway escalators were biting a person every few days, before brushes were added a few years ago. Consolidation of small shops into department stores and then malls (which did/do have escalators, but no/few walkways even now). But small shops continued until 1950's in midtown Manhattan. With lots of elevated trains, thinking "and soon there will be something like it at ground level" doesn't seem implausible. But rail is a tech sweet spot. Why doesn't NYC 5th avenue now have an airport-like walkway? Lack of crowd backpressure from corners? So maybe the failure mode was to greatly underestimate cost, plus safety? [1] picture of a house being trucked: http://www.seattletimes.com/seattle-news/historic-kirkland-house-picked-up-and-moved-down-the-street/ http://www.seattletimes.com/seattle-news/historic-kirkland-h... Another http://www.dailymail.co.uk/news/article-2709261/Moving-house-Entire-historic-DC-apartment-block-hoisted-wheels-sent-road-make-way-new-development.html http://www.dailymail.co.uk/news/article-2709261/Moving-house...