What are those grids of glass in the sidewalk and why are they purple? • Hacker News Board

Re: What are those grids of glass in the sidewalk and why are they purple?

#11

Post by daxorid » Fri, Jan 03, 2020, 9:50 PM UTC

This is interesting, but raises a question. The article mentions:

In San Francisco, vault lights are mostly used to illuminate sub-sidewalk basements — ie. basements that extend under the sidewalk.

How does this work, legally? Where I live, sidewalks are property of the city (or the HOA, in some cases), and I'd presume the same in SF. Does the title of the sidewalk-adjacent property allow you to excavate N feet beyond the property line? Or is the sidewalk instead a publicly-managed easement on your own property? Who pays for installation and maintenance of the vault lights? How does coordination of engineering/construction of the sidewalk-basement boundary work?

Re: What are those grids of glass in the sidewalk and why are they purple?

#12

Post by iDemonix » Fri, Jan 03, 2020, 9:50 PM UTC

robk wrote: post #7

These are ubiquitous in London

And many other parts of the UK. I've seen a fair amount in both Oxford and Nottingham.

Re: What are those grids of glass in the sidewalk and why are they purple?

#13

Post by hinkley » Fri, Jan 03, 2020, 9:52 PM UTC

AstroJetson wrote: post #3

I had a sail boat where the prior owner had installed 4 of these in the cabin roof. They were little domes and did a good job of lighting the cabin in the day, and marking a path at night.

I learned about these many years ago, but the whole "you can see a fire in the hold" angle never occurred to me. Accurate, useful, and macabre.

Re: What are those grids of glass in the sidewalk and why are they purple?

#14

Post by glangdale » Fri, Jan 03, 2020, 9:52 PM UTC

Thaddeus Hyatt, the inventor of those grids, has a fascinating history, including backing militant abolitionists (I think it's unknown whether he bankrolled John Brown) and being jailed by the Senate (?) for refusing to testify.

Re: What are those grids of glass in the sidewalk and why are they purple?

#15

Post by vidanay » Fri, Jan 03, 2020, 9:53 PM UTC

daxorid wrote: post #11

This is interesting, but raises a question. The article mentions: In San Francisco, vault lights are mostly used to illuminate sub-sidewalk basements — ie. basements that extend under the sidewalk. How does this work, legally? Where I live, sidewalks are property of the city (or the HOA, in some cases), and I'd presume the same in SF. Does the title of the sidewalk-adjacent property allow you to excavate N feet beyon…

I would guess these situations pre-date any of the current zoning laws.

Re: What are those grids of glass in the sidewalk and why are they purple?

#16

Post by dualboot » Fri, Jan 03, 2020, 9:56 PM UTC

vidanay wrote: post #15

daxorid wrote: post #11

This is interesting, but raises a question. The article mentions: In San Francisco, vault lights are mostly used to illuminate sub-sidewalk basements — ie. basements that extend under the sidewalk. How does this work, legally? Where I live, sidewalks are property of the city (or the HOA, in some cases), and I'd presume the same in SF. Does the title of the sidewalk-adjacent property allow you to excavate N feet beyon…

I would guess these situations pre-date any of the current zoning laws.

This is correct.

Re: What are those grids of glass in the sidewalk and why are they purple?

#17

Post by pkamb » Fri, Jan 03, 2020, 9:57 PM UTC

taeric wrote: post #2

I thought this was going to be in Seattle. :) It is neat to notice these all over the place. The underground tour is more than a little crazy to see just how built up the city literally is. My favorite related topic were the spite mounds.

The new Seattle waterfront sidewalks have a similar inlayed motif of large purple glass tiles. Was cool to notice the design inspiration.

https://www.washington.edu/news/2017/05/18/seattle-seawalls-...

https://www.kuow.org/stories/seattle-s-new-seawall-was-built...

Re: What are those grids of glass in the sidewalk and why are they purple?

#18

Post by bynkman » Fri, Jan 03, 2020, 10:07 PM UTC

I know of a few places in Kansas City that have under sidewalk vaults. In some of those places they have warning signs about not parking. Here's one. https://bit.ly/36qPLvy

Re: What are those grids of glass in the sidewalk and why are they purple?

#19

Post by im3w1l » Fri, Jan 03, 2020, 10:07 PM UTC

One thing I would have liked the article to explain is when this is preferable over solid glass.

Re: What are those grids of glass in the sidewalk and why are they purple?

#20

Post by vineyardmike » Fri, Jan 03, 2020, 10:08 PM UTC

hinkley wrote: post #8

taeric wrote: post #2

I thought this was going to be in Seattle. :) It is neat to notice these all over the place. The underground tour is more than a little crazy to see just how built up the city literally is. My favorite related topic were the spite mounds.

I think the Seattle Tour has a bunch of factoids of which each guide chooses their own subset. First time I took the tour, they mentioned that a bunch of the material for raising the streets came from San Franscisco, which had quite a thirst of lumber (and would occasionally catch fire and burn down, boosting that demand). Flat bottom boats hold a lot of bulky cargo, but they're a nightmare when empty. So on the retu…

That tour is great! I take everyone who visits seattle to it. I've had the same tour guide, and each time was different as well.