Air rushing into a tube could pneumatically propel, impact, or damage a capsule, or cause capsules to collide. To mitigate this risk, if a big leak is sensed, the section of tube is isolated, and traffic is rerouted, and the isolated tube is flooded with air along the entire length. This air is admitted as fast as possible without causing the capsules to decelerate faster than survivable. In this way, a sudden tube breach will damage fewer capsules. The high speed routes will be underground -- so the possibility of a broken tube is much less.
Why wouldnt a crack in the tube cause the system to lose suction and launch the capsule backwards?
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