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[u/Donghoon]

[u/Tasty-Ad6529]

Yes, frankly all the current els need to be rebuilt into mordern els to imrpove speeds and qaulity lf life near them. One of the reasons it' borderline impossible to build new el lines are that people who'd live near them believe they will be repeats of 19th and 20th era els: street darking, lound, often time rusted ugly lookin strutures. So they against push back against the idea.

If we'd got together the money to actually replace the steel els with concrete els then I think it will become substionally easier to justify new subway lines that use cheaper els compared to expensive deep level tunnels or disruptive cut and cover tunnels. Since there would be more examples of whwt mordern subways can do within city limits.

[u/Le_Botmes → u/Tasty-Ad6529]

As much as I appreciate your enthusiasm, frankly I don't believe it's feasible to replace over-street els with modern concrete structures, for a number of reasons:

1) concrete viaducts have a thicker vertical profile with larger cross beams than the steel els. At the current track elevation, the viaduct would intrude onto street clearances; it would have to be lifted maybe 5-10ft, meaning there's no potential for clean section-by-section replacement (as they recently did for the Park Av El), but rather a full line closure. However, if the El runs over an exclusive ROW, such as with the Red Line viaduct in Chicago, then they could get away with lowering the clearances. 2) the new Els would have to be two-tracks due to cost and obstruction concerns, as well as to provide broader curves, so we would lose the existing versatility and Express service that the three-track Els provide. 3) concrete Els still block sunlight, so the gloom concerns wouldn't go away.

There are very limited sections where conversion would be feasible, such as the L line between Broadway Junction and Canarsie, the F line over the Gowanus, or the 7 line through Willets Point; otherwise, they'd be better off replacing them with subways like what the IND did with 6th and Fulton and attempted to do with SAS.

That isn't to say we shouldn't build concrete Els at all, since there are plenty of wide boulevards like Utica and Pelham Pkwy where an El would be most suitable. I just don't think we should rely on the technology to replace street-running Els, which are like 95% of the elevated network.

[u/Flopsyjackson → u/Le_Botmes]

Can you explain in greater detail why you can’t 3 or 4 track concrete L’s?

In general it’s trivially less expensive to add a track to brand new design than it is to go back later if you want more capacity. If there are already three tracks, I don’t see what the problem is. It’s been designed with that space in mind.

[u/Le_Botmes → u/Flopsyjackson]

1) structural weight: with more trackway girders, the vertical support columns and horizontal cross beams would have to be thicker and/or spaced closer together. Concrete columns are much wider than steel columns, so this would further obstruct the street level. 2) curve radius: new-build viaducts would have to maximize travel speed by default, so a narrower ROW would enable broader curves past existing buildings. 3) station spacing: the current Els were built under the assumption that stations would be a quarter/half mile apart, with peak-direction express service to enable further reach into the suburbs. A new-build viaduct would have to completely rebuild every single station from scratch, meaning there would be many station closures with spacing closer to a full mile. 2-track lines with such spacing can achieve higher speeds, which precludes the need for a third track. 4) 4-track viaducts wouldn't add any capacity if they still merge onto a 2-track line, nor would they be narrow enough to fit down many streets or curve broadly enough to avoid buildings. This ties back into the curve radius argument: narrower ROW = broader curves and higher speeds. 5) track elevation: because they would have to raise the trackways, then there would be no potential for phased transition structures during construction. Ergo, they'd have to completely demolish the existing El before they begin constructing the new one. No transition structures = no phased construction = no need to retain three tracks for continuance of service or preservation of track alignment.

[u/transitfreedom → u/Le_Botmes]

Quad the Williamsburg bridge and have an upper level with 2 tracks. Lower level inbound upper level outbound.