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Thread: Limit arterial surface street to 4 travel lanes

  1. #1
    Cyburbian
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    Limit arterial surface street to 4 travel lanes

    I'm updating our transportation element, with a general policy section first, which is supposed to inform other decisions, namely our Major Street and Collector Plan. The street plan was last updated in the mid 90's, and from my understanding, was based on a typical 4-step travel demand model. As a result, the plan calls for everything from 10-lane freeways to 6 and 8 lane surface arterials, regardless of existing or planned adjacent land use.

    As a transportation planner trying to balance transportation needs with land use/community concerns, 6 and 8 lane arterial surface streets seem excessive to me. I've read work by Walter Kulash, Ian Lockwood, Rick Hall and other engineers arguing that urban arterials shouldn't exceed 4 travel lanes, in consideration of ROW costs, crossing distance for pedestrians and safety of drivers changing lanes. This was echoed by my former MPO director in Greenville, SC, which has a handful of 7-lane arterials (6 travel lanes, plus center turn lane), which can be maddening to drive on in consideration of high speeds and erratic lane-changing.

    Overall, it seems like communities have to put a cap on lane capacity at some point if they're going to preserve and enhance land use and other objectives. Is it unrealistic to cap existing arterials at their 4 travel lanes? The main challenge to this is that Nashville's road system is set up from radial pikes, with limited and often opposed network connectivity between them.

    Still, 6 and 8 travel-lane roads conjure up highway conditions, not anything approaching an urban environment that supports walkability or varied land-use. I'm curious for thoughts.

  2. #2
    Cyburbian Luca's avatar
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    From direct European experience, I would say that IF:

    a) there are reasons to cross from one side of the arterial to the other
    b) the streetscape on both sides of the arterial is interesting and pedestrian friendly
    c) there is sufficient tree shade / medians, etc.
    d) pedestrian crossing points are sufficiently near and allow crossing time

    Then you can have 3-4 lanes each way without destroying the neighborhood.
    Life and death of great pattern languages

  3. #3
    Cyburbian Flying Monkeys's avatar
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    Quote Originally posted by Tall Fella' View post
    , Ian Lockwood, Rick Hall and other engineers arguing that urban arterials shouldn't exceed 4 travel lanes, in consideration of ROW costs, crossing distance for pedestrians and safety of drivers changing lanes.
    I know these gentlemen. Rick Hall will tell you that you can build anything you want, as long as you are willing to sign & seal it. That includes excluding design that promotes safe travel, and creating roads that will not work.

    Ian Lookwood was a planner in West Palm Beach and has been involved in some interesting stuff... I like his design sense. You forgot to throw in Dan Burton.

    The problem here is that what was done in West Palm may not work in XX(fill in your town). And there are some tradeoffs... Congestion for XX(fill in the blank).

    Having said that...
    I think that limiting arterials to 4 lanes in a R/W limited area is a no brainer....
    I think that limiting urban arterials (commercial areas) to 4 lanes is a good idea...

    However, if you can not widen, and the traffic demand is there, you need to start looking into efficient strategies to move traffic, and into widening or adding other routes. Do not let the inclusion of limitations look like or turn into a moratorium on road building. (my advice)
    What’s in a name? – Your reputation….:)

  4. #4
    Cyburbian DetroitPlanner's avatar
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    I'd be concerned about anything that hampers your options or puts capacity ahead of safety. For example, a three or five lane road would be much more safer than a four lane road with no turn lanes. I've seen instances where a four lane road turned into a three lane road made a great improvement in how traffic flowed; and other instances where it has caused traffic to choke.

    Large roads such as Lakeshore Drive in Chicago work very well if implemented correctly. Folks can cross over from the Lake side to the city side quite easily through either tunnels (where it is limited access) or at grade (where it is not limited access). There are also many examples of wide roads that work very well intot he urban fabric of my hometown. Those include Woodward S of Campus Martius and Gratiot by Eastern Market.

    One has to be very selective in their approach to widening roads as besides the high ROW costs the mainetenance costs of wide roads are much higher than they are for skinnier roads when placed in the same environment.
    We hope for better things; it will arise from the ashes - Fr Gabriel Richard 1805

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