NFPA requirements for road tunnels is an emergency exit every 1000ft/300m. Cross-passages to another tunnel are acceptable, including a parallel travel tunnel i

NFPA requirements for road tunnels is an emergency exit every 1000ft/300m. Cross-passages to another tunnel are acceptable, including a parallel travel tunnel if there's automatic traffic control. They may also be stairs or ramps. Secondary tunnels are not common; typically they are for long and/or deep tunnels. Dunno if the Vegas system would qualify as a road tunnel (thus NFPA 502) or some sort of transit tunnel, which might be a different thing. (I've not seen such exits provided in subway tunnels; emergency procedure seems to be "walk back to the station".) But in a short shallow system like in Vegas, they could have periodic cross-passages or stairs to the surface. Dunno if they do; never been in it.