Ep. 42 – What’s a Diverging Diamond and Why Wake Forest Road?

The NCDOT plans to install a few more diverging diamond interchanges in the state in the coming years. Plans for one at Wake Forest Road are causing a bit of a stir. We spoke with the NCDOT about this project. While DDIs are known for improving car congestion, some residents are concerned about how this will impact pedestrians and bicyclists.

An animation from the NCDOT showing how diverging diamonds work. This one is at I-40 and Highway 123.

The public can still comment on this project. The updated plans will be released this fall with another round of public meetings, so keep an eye out.

Video: Explanation and Depiction of a DDI РNCDOT

Diverging Diamond Interchange Could Ease Triangle Road Congestion – WRAL, March 2, 2015

Is Wake Forest Road at the Beltline a good place for a ‘diverging diamond?’ – News & Observer, May 14, 2018

One thought on “Ep. 42 – What’s a Diverging Diamond and Why Wake Forest Road?

  1. Great Episode, thank you! You asked some really good questions.

    I thought Sean evaded many of the tougher ones:

    FHWA manual is not evidence that DDI’s are safer for pedestrians. No ped researchers / advocates are pushing this kind of treatment.

    NCDOT will not admit that any of their projects induce demand. none of their traffic models take it into account. They do plan in response to demand, but that doesn’t mean that induced demand will not also occur. I find it particularly frustrating that NCDOT consistently denies their projects are subject to this well-documented phenomenon.

    If I understood correctly, there will be no signals that stop traffic for pedestrians to cross. Instead some sort of “coordination”. This is a step down from current ped service.

    There was no commitment to try to conform to Raleigh’s comp plan (calls for a separated bike path).

    Keeping bus stops open during construction is not the same as reconciling a project to ease motoring with a desire to promote walkable communities and reduce car-dependence.

    Overall, Sean’s answers were what I would expect from a project booster or marketer, instead of a balanced discussion of pros and cons. I would love to hear you interview a qualified planner that focuses on walkabilty and pedestrian safety. Don Kostelec has extensive experience working with NCDOT and would provide great balance representing the pedestrian perspective. He’s a principal at http://vitruvianplanning.com/about/

    Thanks again, love your show!

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