As safe as any cave open to the public, which there are many of in state and federal parks often with only 1 or 2 exits.
Also, barring an act of terrorism, it's probably as safe as driving a car, safer than skiing (water or snow), exponentially safer than sky-diving etc.
>What happens if there is a fire and you are in the sixth tube down?
Compared to the feat of actually tunneling the machine, boring small escape tubes would be relatively trivial. Employ magnetic-electric security doors that can be remotely released or unlock in the event of a power failure and anyone able bodied could climb a ladder out, make them wide enough to get a rescue harness down and fabricate in an anchor point for a safety line and anyone not capable could be lifted out not unlike how rescue helicopters lift people with a winch. And really, the operator could install the harnesses and winches too and have them be both electric with a way to easily connect them to an external power source and/or manual for redundancy. All you'd have to do is test them once or twice a year and lubricate as necessary.
I'm pretty risk-averse but I wouldn't hesitate to use one, even without escape shafts.
As safe as any cave open to the public, which there are many of in state and federal parks often with only 1 or 2 exits.
Also, barring an act of terrorism, it's probably as safe as driving a car, safer than skiing (water or snow), exponentially safer than sky-diving etc.
>What happens if there is a fire and you are in the sixth tube down?
Compared to the feat of actually tunneling the machine, boring small escape tubes would be relatively trivial. Employ magnetic-electric security doors that can be remotely released or unlock in the event of a power failure and anyone able bodied could climb a ladder out, make them wide enough to get a rescue harness down and fabricate in an anchor point for a safety line and anyone not capable could be lifted out not unlike how rescue helicopters lift people with a winch. And really, the operator could install the harnesses and winches too and have them be both electric with a way to easily connect them to an external power source and/or manual for redundancy. All you'd have to do is test them once or twice a year and lubricate as necessary.
I'm pretty risk-averse but I wouldn't hesitate to use one, even without escape shafts.