5 ms·

You might need to be amazed at the savings at scale. The land area covered by a few city blocks of road compared to a driveway is pretty large. The $1.5M is lik

You might need to be amazed at the savings at scale. The land area covered by a few city blocks of road compared to a driveway is pretty large. The $1.5M is likely a pretty good buy. Napkin calc: assuming a driveway that's 20 feet wide and 30 feet long, the area will be 600 feet^2. The typical residential road's going to be something like 30 feet wide (enough for a parked car and two opposing lanes with comfort) and a guess at a block being like 1/20 of a mile, or 250 feet; that gives each city block of road about 7500 feet^2. So guessing conservatively, about one city block is probably at least 10 times larger than the driveway. And that's before the actual road complexity. A city road also likely has to account for sewage, powerlines, telecom cables, drainage, etc. There's also a trade-off in road design: your friend likely never wants to build his driveway again, so he'll want something permanent like cement. But the city may want to make different trade-off; blacktop can be more easily maintained and expanded and upgraded than pavement, but also costs more in the long run (but pavement is more expensive up front).

XorNot 10y ago
Also account for time - you absolutely can't close down the entire city block, so all the major construction tends to have to be scheduled at night.
- maxerickson 10y ago
  The majority of miles of paved city blocks in the US can easily be shutdown during the day. The streets are often a grid, so there are easy detours. It's not so simple in high density areas, but those are a small portion of the paved streets by area.
  - Bartweiss 10y ago
    You really can't, not for any substantial length of time. First, you create horrible traffic distortions - a place like LA or Boston simply can't load adjacent streets with more traffic and expect good outcomes. Second, you effectively shut down any business on that block, especially in an area that isn't walking friendly. You also cause huge problems for anyone living and parking at that street. High density areas are a small portion of streets by area, but not by use (and therefore wear) or by cost. I suspect that a mile of highway is often cheaper to replace than a block of dense urban road.
    - maxerickson 10y ago
      In this small town there's like 3 or 4 miles of commercial streets and dozens and dozens of miles of paved streets. Of course streets don't get shut down for weeks of prep work, but the paving will be done when the machine and crew are available and probably not at night.
      - Bartweiss 10y ago
        Ok, totally true. I was thinking in terms of the article, so primarily about NYC. In places like that there's a lot of frontage which is basically never supposed to close.
dclowd9901 10y ago
By your own explanation, it should cost maximum $600,000, especially since a well trained crew could leverage their skill at scale. But this even seems like a lot to me: $60k is an enormous sum to pave 20 feet of driveway. I was looking at having it done and it was closer to $6k so it should be even less to pave 4 blocks. This issue, to me, is hugely concerning. Why did one mile of the bay bridge cost as much to build as funding NASA for 6 years?
- HCIdivision17 10y ago
  Oh no, my estimates were really in favor of the parent's comparison. That $600k is a lowest-bidder minimum, expecting to redo in a month when it fails. I'd be interested to know more about the breakdown, and I'd bet at least some municipalities are required to share it. A well trained road crew is likely pretty expensive, and as others noted, there's a lot more to a road than a driveway. Most driveways I've seen are largely cement planks, whereas a road is layers of differing materials to ensure frequent use doesn't destroy it too quickly. As for bridges. Eugh. I dunno. Those things are often crazy expensive. I wouldn't be surprised though, since that bridge is rather large and suffers a lot more wear and tear than NASA. I mean, they just need to punch a few one-time use rockets into space, but that bridge has to deal with thousands of semis. Space is a nasty place, but I'm betting thousands of trucks barreling over is harder to deal with year in and out.
- Vraxx 10y ago
  Just going off of the comment you're responding too, that $600,000 corresponds to one block when the original example specified 4 blocks for $1.5 mil. I don't claim to know anything about street paving economics, I just wanted to point out the disconnect.
- zrail 10y ago
  The load and traffic that a typical driveway sees is far less than what a city block would be expected to see. There's more concrete, rebar, gravel, etc for every square foot of surface. Interstate-grade highways have 8-10 inches of reinforced concrete. Driveways are typically 4 inches and are not reinforced. The same goes for asphalt, if that's what they're using. It'll be cheaper because it's not designed to last as long, but the scaling factors hold.

XorNot 10y ago

Also account for time - you absolutely can't close down the entire city block, so all the major construction tends to have to be scheduled at night.

maxerickson 10y ago
The majority of miles of paved city blocks in the US can easily be shutdown during the day. The streets are often a grid, so there are easy detours. It's not so simple in high density areas, but those are a small portion of the paved streets by area.
- Bartweiss 10y ago
  You really can't, not for any substantial length of time. First, you create horrible traffic distortions - a place like LA or Boston simply can't load adjacent streets with more traffic and expect good outcomes. Second, you effectively shut down any business on that block, especially in an area that isn't walking friendly. You also cause huge problems for anyone living and parking at that street. High density areas are a small portion of streets by area, but not by use (and therefore wear) or by cost. I suspect that a mile of highway is often cheaper to replace than a block of dense urban road.
  - maxerickson 10y ago
    In this small town there's like 3 or 4 miles of commercial streets and dozens and dozens of miles of paved streets. Of course streets don't get shut down for weeks of prep work, but the paving will be done when the machine and crew are available and probably not at night.
    - Bartweiss 10y ago
      Ok, totally true. I was thinking in terms of the article, so primarily about NYC. In places like that there's a lot of frontage which is basically never supposed to close.

dclowd9901 10y ago

By your own explanation, it should cost maximum $600,000, especially since a well trained crew could leverage their skill at scale. But this even seems like a lot to me: $60k is an enormous sum to pave 20 feet of driveway. I was looking at having it done and it was closer to $6k so it should be even less to pave 4 blocks. This issue, to me, is hugely concerning. Why did one mile of the bay bridge cost as much to build as funding NASA for 6 years?

HCIdivision17 10y ago
Oh no, my estimates were really in favor of the parent's comparison. That $600k is a lowest-bidder minimum, expecting to redo in a month when it fails. I'd be interested to know more about the breakdown, and I'd bet at least some municipalities are required to share it. A well trained road crew is likely pretty expensive, and as others noted, there's a lot more to a road than a driveway. Most driveways I've seen are largely cement planks, whereas a road is layers of differing materials to ensure frequent use doesn't destroy it too quickly. As for bridges. Eugh. I dunno. Those things are often crazy expensive. I wouldn't be surprised though, since that bridge is rather large and suffers a lot more wear and tear than NASA. I mean, they just need to punch a few one-time use rockets into space, but that bridge has to deal with thousands of semis. Space is a nasty place, but I'm betting thousands of trucks barreling over is harder to deal with year in and out.
Vraxx 10y ago
Just going off of the comment you're responding too, that $600,000 corresponds to one block when the original example specified 4 blocks for $1.5 mil. I don't claim to know anything about street paving economics, I just wanted to point out the disconnect.
zrail 10y ago
The load and traffic that a typical driveway sees is far less than what a city block would be expected to see. There's more concrete, rebar, gravel, etc for every square foot of surface. Interstate-grade highways have 8-10 inches of reinforced concrete. Driveways are typically 4 inches and are not reinforced. The same goes for asphalt, if that's what they're using. It'll be cheaper because it's not designed to last as long, but the scaling factors hold.