Quote:
Originally Posted by Quixote
The Alternative 6 alignment would largely be a straight tunnel underneath the Santa Monica Mountains, which I would have to think is not an insignificant cost factor. My only disappointment with A6 is the SMB station would be at the West LA Civic Center (either at Corinth or Purdue, rather than Federal like I had hoped). Still, it would be a game-changer for dense West LA / Sawtelle.
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Alternative 6 calls for dual bore tunnels, which due to US fire safety requirements, requires manual mining of emergency escape cross-passages every 800 feet, ventilation shafts to the surface every 6,000 feet, and manually mined crossover sections, which are significant cost factors. The ventilation shaft issue (and driver-operated trains) probably plays into why Alternative 6 has 4-minute headways—you can only have 1 train occupy a ventilation zone at a time.