For underwater tubes, escape hatches would lead to escape capsules.
I should probably clarify that these proposed tubes are quite narrow ranging in width from 2' to 5' with 51" being the supposed optimal width from a cost/capacity perspective. For a 2' diameter tube you would be lying down in a capsule.
Yeah, even if every passenger had emergency scuba gear and could make that trek of up to 1/2 mile to the nearest escape hatch, then what? Emerge from the hatch into the waters of the icy North Atlantic, at a depth of probably 50-100 feet below the surface?
They claim that their build costs are 1/10 that of high speed rail at about $2 million per mile for a 350 mph system. They go on to state that “Some licensees believe that cost will be so low that advertising could pay for most travel, just like it pays for TV, or free Internet.”