Vegas Loop isn’t just tunnels! It is also stations, merge/exit ramps, cross-passages, ventilation chambers, and emergency egress shafts. See pics for the construction of an egress shaft; construction time is ~8 days. Steps: 1. Excavate down to expose the tunnel exterior 2. Install waterproofing, conduit, and rebar, followed by pouring a concrete base slab adjacent to the tunnel 3. Add steel-reinforced concrete walls and backfill the perimeter 4. Pour a concrete roof (leaving an opening for egress) and pave over the structure with asphalt; final surface impact is ~120 square feet Once the structure is complete, a doorway is cut into the tunnel to connect the tunnel to the shaft. Finally, the shaft is built out with stairs, ventilation, standpipe, safety equipment/sensors, access hatch, lighting, and cameras.