Wow, as someone who follows the construction progress of Los Angeles' Purple Line (the only heavy rail transit line currently in active boring in the US) I did

Wow, as someone who follows the construction progress of Los Angeles' Purple Line (the only heavy rail transit line currently in active boring in the US) I did not know how fast that even reaching the speed of a snail would be: If we assume the tunnels are being bored at somewhere near the average of ~100meters/week, and the snail is about ~1000meters/week, that's a 10x speedup in the time to dig right there! The total length of the three segments is about 9 miles (~14,500 meters)[1], with the last segment projected to open in 2027. Digging started in Fall of 2018[2]. Los Angeles is using what looks like 6 TBMS, two for each segment, to dig parallel tunnels. Segment one completed digging in January of 2022[3], and as of August 2023 Metro has delayed full completion of segment one to 2025[4], therefore it appears that even though digging is not the end-all-be-all, it does take up >50% of the entirety of the construction timeline (~4 years digging + 3 years other construction for segment 1, including stations, track, electrical, and testing). Using the article as a guide, then, somehow speeding up the digging by a factor of 10 would mean digging could take as little as 21 weeks or ~5 months months, rather than ~4 years, and reduce the project timeline by 50% from 7 years to 3.5 years! This would be huge for when Los Angeles eventually begins to bore the heavy rail tunnel under the Sepulveda mountain pass, which would be 14 miles, most of it likely tunneled [5]. [1] https://www.metro.net/projects/westside/ https://www.metro.net/projects/westside/ [2] https://twitter.com/metrolosangeles/status/1045831796234113025 https://twitter.com/metrolosangeles/status/10458317962341130... [3] https://thesource.metro.net/2022/01/31/purple-line-tunneling-completed-between-century-city-and-wilshire-rodeo/ https://thesource.metro.net/2022/01/31/purple-line-tunneling... [4] https://twitter.com/numble/status/1709258555117777016 https://twitter.com/numble/status/1709258555117777016 [5] https://www.metro.net/projects/sepulvedacorridor/ https://www.metro.net/projects/sepulvedacorridor/