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Thread: Impact of bridge/street connections

  1. #1
    Cyburbian
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    Impact of bridge/street connections

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    I work in a geographically diverse city, so I encounter everything from rural to urban settings. Being in a place bisected by a river, railroads, etc., I'm currently grappling with two connectivity issues.

    The first concerns a currently rural bend in the river. Its significant topography precludes intense development on most of it, yet its southern tip is fairly flat. The tricker is that the nearest "outside" connection is 5 miles north, along a state highway.

    What effect would a bridge have on the area, and would it be a responsible condition of future development on the river bend or north of it? I realize there are several answers here, one being that the bridge will "induce" travel demand and land development. Another answer could be that adding a bridge would enhance the overall transportation network, reduce trip distances and responsibly support future development on the river bend.

    Overall, have people had experience with a situation like this, or just general impact analysis of new bridges? 2 lane? 3 lane? 4 lane? Any bridge onto the river bend would connect onto a narrow, 2-lane farm to market road.

    The next case involves creating a viaduct connection over a major railyard, upgrading a local residential street into more of an arterial street to provide an east-west connection in an area otherwise limited by rail lines and freeways. See the "Existing" and "Proposed" images for an idea of what could happen here. Again, if anyone has thoughts on how to assess the impact of this, I'd appreciate it.
    Last edited by mendelman; 13 Dec 2007 at 10:10 AM.

  2. #2
    Cyburbian jkellerfsu's avatar
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    Quote Originally posted by Tall Fella' View post
    The next case involves creating a viaduct connection over a major railyard, upgrading a local residential street into more of an arterial street to provide an east-west connection in an area otherwise limited by rail lines and freeways. See the "Existing" and "Proposed" images for an idea of what could happen here. Again, if anyone has thoughts on how to assess the impact of this, I'd appreciate it.
    What are the land uses shown in the diagram?

  3. #3
    Cyburbian Michele Zone's avatar
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    Quote Originally posted by Tall Fella' View post
    The first concerns a currently rural bend in the river. Its significant topography precludes intense development on most of it, yet its southern tip is fairly flat. The tricker is that the nearest "outside" connection is 5 miles north, along a state highway.

    What effect would a bridge have on the area, and would it be a responsible condition of future development on the river bend or north of it? I realize there are several answers here, one being that the bridge will "induce" travel demand and land development.
    <SNIP>
    Again, if anyone has thoughts on how to assess the impact of this, I'd appreciate it.
    When you urbanize an area, it tends to make flooding worse -- both more frequent and more extreme. Rivers generally meander, which is where the bend in the river comes from. So I would wonder if there is a way to model such impacts using a scenario where creating a bridge promoted development in the currently rural, flat southern tip. Can the river system handle the increased run-off from so much of the land being paved over? Or does it potentially alter the course of the river? What happens to current development on the urbanized side should new development promote frequent, severe floods? Do current land values plummet if you start having "100 year floods" every few years? And so on.
    Last edited by Michele Zone; 15 Dec 2007 at 11:17 AM.

  4. #4
    Cyburbian permaplanjuneau's avatar
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    easy answer: no easy answer

    Boy, have you hit on a hot topic for my region. You've probably heard of the Alaskan "bridges to nowhere" that were in the news last year--one of them would replace a ferry that runs every 15-30 minutes depending on the season. The purposes of this bridge? To paraphrase the web site below: 1) Provide access to land which is slated for development in the borough's long-range plans (a "borough" is what we call a "county" in Alaska); 2) Provide regular access to the Ketchikan airport, which is currently only served by ferry (there were no roads on the island that has the airport on it until this project started).

    http://dot.alaska.gov/stwdplng/proje...a/index1.shtml

    A few highlights of the project:
    Of the two bridges required for this connection, the larger will be 200' high--tall enough for Panamax (the largest size vessel that can fit through the Panama Canal) cruise ships to pass under--these are 15-17 story buildings, carrying thousands of passengers and crew.
    The projected cost (out of date, of course)? $315 million.
    The population of the Ketchican Gateway Borough (KGB)? 14,070 in 2000.
    If the residents of the KGB were to fund the project themselves, it would cost them $22,388 each.*

    *note that the KGB road system is not connected to any other road system--that is, the bridge under discussion would not provide access to or from adjacent cities or within the larger region of Southeast Alaska.

    As a side note on this project, the Alaska Department of Labor reports that Ketchikan (the borough and the city) is loosing population, and will continue to do so for the foreseeable future. So what's the need for more land to develop? And is a bridge to an airport (and nothing but an airport) a worthwhile investment?

    To bring this example back to Tall Fella's questions:
    "What effect would a bridge have on the area, and would it be a responsible condition of future development on the river bend or north of it? I realize there are several answers here, one being that the bridge will "induce" travel demand and land development. Another answer could be that adding a bridge would enhance the overall transportation network, reduce trip distances and responsibly support future development on the river bend."

    Assuming that there is development pressure in your area, or that there will be in the future (before the bridge falls down), the bridge will result in urban sprawl unless regulations are in place that prevent that outcome. The fact that you're asking the question leads me to think that protections like this have not been adopted for this area. Clearly (based on nation-wide and international trends), "the bridge will 'induce' travel demand and land development." I fail to see how the first part of the second proposed answer, that "adding a bridge would enhance the overall transportation network," is any different from the first proposed answer. New road access = induced traffic = induced development = increased traffic. All of this changes, however, if you've got adequate development controls in place to ensure that the new bridge and road connection "support [responsible] future development on the river bend."

    On the second question, all I can say is "yikes." The property owners in that neighborhood are going to freak out. Have fun dodging pitchforks and the angry mob that will be wielding them.

  5. #5
    Cyburbian Richi's avatar
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    Looks like industrial/commercial on the lefthand side of the railtard map. If so, is there much interaction between the east side residential and there? The road looks like it cuts thru a single family neighborhood. If there are no sidwalks now and no street trees of value. one might hope that you could get away with your life by promising to give sidwalks, street trees, perhaps better drainage and a much improved look. This coupled with a quicker way to work would be good. Better have some sit downs with neighborhood opinion leaders before you go to far.

    As to the bridge... I don't have enough info for anything more than a guess, but I suspect that a realistic cost/benefit ctudy would turn up to be break even at best. You might drive up some land values, but are likely to drive some down. VMT could also increase.

  6. #6
    Cyburbian jkellerfsu's avatar
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    Quote Originally posted by Richi View post
    Looks like industrial/commercial on the lefthand side of the railtard map. If so, is there much interaction between the east side residential and there? The road looks like it cuts thru a single family neighborhood. If there are no sidwalks now and no street trees of value. one might hope that you could get away with your life by promising to give sidwalks, street trees, perhaps better drainage and a much improved look. This coupled with a quicker way to work would be good. Better have some sit downs with neighborhood opinion leaders before you go to far.

    As to the bridge... I don't have enough info for anything more than a guess, but I suspect that a realistic cost/benefit ctudy would turn up to be break even at best. You might drive up some land values, but are likely to drive some down. VMT could also increase.
    Assuming these land uses, a bridge will generate TRUCK traffic. I only bring this up becasue I deal with truck complaints daily. Aside from the homeowners losing their "quaint" street they will live with trucks.

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