Bacon's Rebellion

Democracy Thrives in Sunlight

The Biggest, Bestest Roundabout Yet

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by

James A. Bacon
in

A 110-foot roundabout, due for completion next spring, will create an attractive southern gateway to the city of Portsmouth’s revitalized downtown. Reports Janie Bryant with the Virginian-Pilot:

The road design eliminates several of the roads now feeding in and out of Crawford Street and frees up extra land on its northwestern side to make room for what will likely be a mid rise residential development.

The added land for development is one of the benefits of the new traffic design but not the main point, city engineer Richard Hartman said. … “This would provide a focal point for downtown. … It’s more of an identity of a destination.”

Downtown Portsmouth, once one of Virginia’s seedier urban districts, is making a tremendous come-back. Overshadowed by the spectacular revitalization of downtown Norfolk across the river, downtown Portsmouth is one of Virginia’s best kept secrets. The city has built on its waterfront and historic buildings to create a very attractive and liveable place. To see other renderings of Portsmouth Vision 2005, visit the Urban Design Associates website.

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4 responses to “The Biggest, Bestest Roundabout Yet”

  1. Ray Hyde Avatar
    Ray Hyde

    The rendererings always have a way of making things look attractive. Isn’t it convenient that those two buildings borderng th circle have curved fronts to reflect the circle? Or is that yet to be completed construction.

    As drawn, this appears to be an attractive focal point, but roundabouts are not a universal answer, and each needs to be evaluated specifically for the needs at hand.

    In Sagamore, one of the most famous circles in the nation, at the end of the Sagamore bridge over the Cape Cod canal has just been replaced with a flyover, due to the many problems and gross congestion the circle caused.

  2. Larry Gross Avatar
    Larry Gross

    roundabouts really are no more or less unique than .. say diamond or cloverleaf interchanges… that while not exact templates… because of site-required variations..

    There are some places that they are not appropriate due to local circumstances but in general, roundabouts do much, much better than traffic signals at VPD of 25K or less..

    roundabouts… move traffic continuously rather than alternating “streams” of traffic.

    They function well no matter at 2am or peak hour… and they function even during power outages.

    The accident rate at roundabouts both in terms of frequency and severity are much lower… and most accidents are fender benders rather than red-light running “t-bone” crashes.

    AND.. they’re usually cheaper than signalized intersections.

    Roundabouts can even have traffic signals… and if they have “smart” signals…that adapt to traffic flow.. they can actually be the best of both pure roundabouts and pure traffic signals.

    Roundabouts are also great for subdivisions because they slow traffic down… and because of this.. multiple subdivisions can be “connected” … which eliminates the need for 3 separate entrances to the frontage arterials.

    But I do agree with Ray.. about the artistic “renderings” which can make a sewage treatment plant look like a wonderful park…. 🙂

  3. Ray Hyde Avatar
    Ray Hyde

    I agree, where they work, they work well.

    I wonder how much open space (or other evenmore valuable space) we would consume by converting numerous signals to circles?

    If we link land use to transportation, and we have a bunch of circles, what will it take to keep the VPD below 25k?

  4. Larry Gross Avatar
    Larry Gross

    Roundabouts don’t have to be huge… their footprints can be close to what a signal requires.

    VPD won’t be affected by roundabouts. VPD comes from land-uses….

    what roundabouts do is related to level of service for whatever existing traffic there is.

    It tends to meter traffic which is a benefit at both ends of traffic. The low end – means – no red lights when there is no traffic… and at the high end – at peak hour – it keeps traffic moving… on all lanes….

    If you had road … say with 5 traffic signals over a couple of miles and replaced all of them with roundabouts –
    the alternating “streams” of traffic would go away… and that assumes the signals are all co-timed with each other and not actually running alternate cycles. So, at the least, roundabouts… would do away with the need on some roads to have expensive multi-signal timing devices.

    But .. if the adjacent land is developed to the point where it will generate in excess of 25K vpd – then you’d have to put traffic signals back into the mix….

    This would be an example where the existing level of service is acceptable to existing residents – and a clear degradation of it.. when more development comes along – and – no easy way for the new development to fully mitigate it’s impact. In other words, new development WILL degrade the level of service.

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