LOS ANGELES | Transportation News & Discussion

[Busy Bee]

It's not the actual tunnel boring that's the issue as modern TBM's have turned that into an efficient and usually speedy thing of beauty. You do have ventilation, fire safety and egress requirements which above ground does not, but ultimately it's mostly the damn stations, which still require the street to be cut-and-cover excavated and/or mined(in rock), which for obvious reasons is wildly expensive and time consuming. But few will doubt the obvious benefits of a fully underground railway. New and exciting solutions are on the horizon though including exploring fitting the stations within the diameter of the bore so all you need to do is mine surface access without needing to dig a battleship sized hole in the ground (or mine it out of rock). This is most notably being explored in one of the Sepulveda single bore heavy rail options.

[craigs]

Originally Posted by Busy Bee

It's not the actual tunnel boring that's the issue as modern TBM's have turned that into an efficient and usually speedy thing of beauty. You do have ventilation, fire safety and egress requirements which above ground does not, but ultimately it's mostly the damn stations, which still require the street to be cut-and-cover excavated and/or mined(in rock), which for obvious reasons is wildly expensive and time consuming.

Also, relocating utilities adds to the time and cost of tunneling, especially in old neighborhoods and CBDs. I know SF's 2-mile Central Subway light rail extension was significantly delayed by the need to cap and relocate steam pipes, gas lines, water and sewer, electrical, etc.

But few will doubt the obvious benefits of a fully underground railway.

No argument here. The Los Angeles metro is 100% underground--are there any others in the US?

[jbermingham123]

Originally Posted by craigs

No argument here. The Los Angeles metro is 100% underground--are there any others in the US?

I believe DC is fully underground

Boston is mostly underground

[Nouvellecosse]

DC Metrorail system is less than half underground overall, but the majority is underground within the DC limits. The big exception being the red line between Union Station and the DC limits near Silver Spring where it runs along a surface mainline rail corridor.

[craigs]

Originally Posted by jbermingham123

I believe DC is fully underground

Boston is mostly underground

The MBTA has a lot of surface and elevated heavy rail outside the central city. I used to take the Orange Line from Somerville to Forest Hills, and most of that was not underground.

[jbermingham123]

welp, 0/2 for me then

good to know!

[jmecklenborg]

Originally Posted by FromSD

But I definitely think the street running portion of the A line along Washington south of DTLA would benefit from being elevated, as would the E line from USC to Crenshaw. And Metro really needs to do something to grade separate the junction of the A and E lines south of downtown. That is a real bottleneck.

Elevating this section of the line would mean having to climb over the I-10:




It's definitely possible, even if the at-grade Pico station remains as-is, but it would probably be pretty unsightly. They'd want to do a flying crossover at the junction, so that would also be pretty ugly.

[ssiguy]

Montreal's Metro is 100% underground due to being rubber tired and rubber doesn't works so well in snowy climates. Montreal's new REM {light Metro} is mostly above ground due to using standard LRT trains.

[ardecila]

Originally Posted by Busy Bee

New and exciting solutions are on the horizon though including exploring fitting the stations within the diameter of the bore so all you need to do is mine surface access without needing to dig a battleship sized hole in the ground (or mine it out of rock). This is most notably being explored in one of the Sepulveda single bore heavy rail options.

VTA is doing this for the BART San Jose extension. It is *more* expensive than a traditional sequence with cut/cover stations, due to the increased volume of soil removal and the (much) deeper stations.

[jmecklenborg]

Originally Posted by ardecila

VTA is doing this for the BART San Jose extension. It is *more* expensive than a traditional sequence with cut/cover stations, due to the increased volume of soil removal and the (much) deeper stations.

This might be the case for BART, since the platforms are 700 feet long - pretty much the longest rapid transit platforms in the world. By contrast, the LA light rail platforms are 250 feet long.

Any new-build subway system can build much more of its lines as cut-and-cover. When subsequent lines are built, they typically must be built deeply to pass beneath earlier lines. The next phase of the Second Ave. subway in NYC, for example, will have a very deep station at 125th St. because it will be built perpendicular to the existing existing 125th St. Lexington Ave. subway station...which is directly below Metro North's elevated station.

Similarly, the addition of elevated transit lines to cities that have expressway networks means that the lines might have to pass very high above the existing expressways.

[ardecila]

Originally Posted by jmecklenborg

This might be the case for BART, since the platforms are 700 feet long - pretty much the longest rapid transit platforms in the world. By contrast, the LA light rail platforms are 250 feet long.

Any new-build subway system can build much more of its lines as cut-and-cover. When subsequent lines are built, they typically must be built deeply to pass beneath earlier lines. The next phase of the Second Ave. subway in NYC, for example, will have a very deep station at 125th St. because it will be built perpendicular to the existing existing 125th St. Lexington Ave. subway station...which is directly below Metro North's elevated station.

Similarly, the addition of elevated transit lines to cities that have expressway networks means that the lines might have to pass very high above the existing expressways.

If you can build the platforms within the tunnel bore, then platform length isn't a huge driver of cost. That's actually a selling point, since future platform extensions are very feasible to add capacity.

But regardless of platform length, you still need two exits from an underground station by code, and when the tunnel is very deep then both exits are extremely expensive to build with multiple escalators, high-speed elevators, and complicated structural systems, plus ventilation needs increase as well.

[jmecklenborg]

Originally Posted by ardecila

If you can build the platforms within the tunnel bore, then platform length isn't a huge driver of cost. That's actually a selling point, since future platform extensions are very feasible to add capacity.

The tunneled section for a 700-foot platform would need to be straight and level for a longer length and perhaps diverted in one direction or another, slowing travel speed of the trains for the next 100+ years, in order to position the platform ideally for entry points.

But regardless of platform length, you still need two exits from an underground station by code, and when the tunnel is very deep then both exits are extremely expensive to build with multiple escalators, high-speed elevators, and complicated structural systems, plus ventilation needs increase as well.

Incidentally, from what I've observed from online videos (I haven't been there), it appears that some or perhaps many of Moscow's very, very busy subway stations (far busier than NYC or any other system in Europe) only have one entrance/exit point. Aside from safety issues in the event of an emergency, it appears to require full-time staff in some stations to mange all of the foot traffic.

[ssiguy]

^^^ Moscow's great Metro system was built by Stalin using, effectively, slave labour. Hundreds died in its construction so I think Moscow isn't the best analogy.

[Illithid Dude]

I visited Moscow in 2020 and was struck by how few entrances each Metro station had. Many only had one or two, though of course the larger transfer stations often had more. The stations were also often spaced further apart than similarly dense Asian and European capitals. Kyiv had similar station spacing and entrance designs. However, in Practice, I found it didn't bother me much. If anything, having to walk a few extra blocks encouraged me to explore the city further. The Moscow Subway also had incredible headways, with trains arriving every few minutes, or less. It didn't hurt that the stations themselves are architectural marvels, and are easily the nicest I have ever been in. Honestly, they may be the nicest in the entire world. I am currently in Seoul, which is riddled with subway entrances, though the system has a few surprising faults. The stations are plagued with poor wayfinding, and the headways are surprisingly low. Often times, the trains only come once every six or so minutes, and I have experienced a few delays. Tomorrow I head to Shanghai, and am extremely curious to see how their famed subway system fares. I will of course report back!

[hughfb3]

Originally Posted by Illithid Dude

I visited Moscow in 2020 and was struck by how few entrances each Metro station had. Many only had one or two, though of course the larger transfer stations often had more. The stations were also often spaced further apart than similarly dense Asian and European capitals. Kyiv had similar station spacing and entrance designs. However, in Practice, I found it didn't bother me much. If anything, having to walk a few extra blocks encouraged me to explore the city further. The Moscow Subway also had incredible headways, with trains arriving every few minutes, or less. It didn't hurt that the stations themselves are architectural marvels, and are easily the nicest I have ever been in. Honestly, they may be the nicest in the entire world. I am currently in Seoul, which is riddled with subway entrances, though the system has a few surprising faults. The stations are plagued with poor wayfinding, and the headways are surprisingly low. Often times, the trains only come once every six or so minutes, and I have experienced a few delays. Tomorrow I head to Shanghai, and am extremely curious to see how their famed subway system fares. I will of course report back!

Wow! I would one day like to see those beautiful stations... Those Moscow headways remind me of being in Vancouver and their skytrain Expo and Millennium lines had trains coming every 2-3 min, a train would leave and I could see the next train on its way. Ive never witnessed that kind of headway, even visiting western European cities. I really hope the Sepulveda Pass Transit corridors wins and selects the skytrain technology for LA, I need those headways to become a standard here. These Light Rail headways are pretty basic...

[jmecklenborg]

Originally Posted by hughfb3

Wow! I would one day like to see those beautiful stations... Those Moscow headways remind me of being in Vancouver and their skytrain Expo and Millennium lines had trains coming every 2-3 min, a train would leave and I could see the next train on its way. Ive never witnessed that kind of headway, even visiting western European cities. I really hope the Sepulveda Pass Transit corridors wins and selects the skytrain technology for LA, I need those headways to become a standard here. These Light Rail headways are pretty basic...

Moscow can achieve very tight headways (90 seconds) because there is no interlining. In Washington, DC, the red line is completely separate from the rest of the Metro network and so has no junction delays. In LA, people here have suggested separating the Wilshire (D) and Vermont (B) subways should the existing Vermont subway be extended southward. However, from what I understand, the frequency of the existing Vermont Ave. line is limited because the long bored tunnel between Universal City and Hollywood can only have one train in it at a time due to inadequate fire suppression or some other safety requirement. Even though it is a two-track tunnel, it must always run like a single-track tunnel.

[Nouvellecosse]

^ At the same time, Vancouver Skytrain has a branch where the main line splits into two like the LA subway. But they're treated as branches of the same line rather than as two lines with separate names.

[craigs]

L.A. Metro’s D Line hits a milestone: Tunneling is complete for expansion to the Westside


A construction worker at the future Wilshire/Fairfax stop on Monday as L.A. Metro celebrated completion of tunneling for the subway’s D Line extension into the Westside. (Etienne Laurent / For the Times)

Caroline Petrow-Cohen
Los Angeles Times
April 2, 2024

After five years of construction and numerous delays, crews have finished tunneling operations for the 9-mile westward expansion of the Metro D Line, which will stretch from the current terminus in Koreatown to a new Westwood/VA Hospital Station.

The expansion project will add seven Metro stations and a high-speed connection from downtown Los Angeles to the Westside, according to L.A. Metro’s website. Construction of the $9.5-billion project began in 2019.

“As one of L.A.’s busiest areas, the Westside is the region’s second-largest job center,” Metro says on its website. “We are closer than ever to connecting busy areas and improving travel for everyone who lives, works and plays in L.A. County.”

The extension of the D Line, also known as the Purple Line, is taking place in three phases in sections that are roughly 3 miles long each.

Section 1, which will include the Wilshire/La Brea Station, Wilshire/Fairfax Station and Wilshire/La Cienega Station, is slated to open first, in 2025.

Section 2, consisting of the Wilshire/Rodeo Station and Century City/Constellation Station, is set to open in 2026. Section 3 is expected to be completed in 2027, with Westwood/UCLA and Westwood/VA Hospital stations.

. . . .

[Illithid Dude]

Fantastic. Now let's get that sucker to 4th street!

[citywatch]

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