Incomplete Roundabouts

We’ve noticed two tendencies when roundabouts are discussed in the transportation world.

Not all the same

First, they’re often all treated the same. But just like roads, we can’t make gross generalizations about all roundabouts. Some roundabouts are pleasant one-lane affairs that are easy to navigate by bicycle. At the other end of the spectrum are multi-lane, multi-roundabout disasters.

It seems some road agencies building roundabouts to handle a much greater vehicle capacity. That means simple one- or two-lane roundabouts turn into bigger monsters. An example of this is at W. Maple Road and Farmington Road. Both are two lane roads that expand to 5- and 6-lane roads before entering a triple-lane roundabout. Not only is it not bicycle friendly, it’s not designed to let cyclists easily transition on the adjacent pathways to avoid it.

AASHTO‘s latest bicycle design guidelines say roundabouts should not be built like this. They should be designed for current needs and made easily expandable for future needs.

Single‐lane roundabouts are much simpler for bicyclists than multilane roundabouts, since they do not require bicyclists to change lanes, and motorists are less likely to cut off bicyclists when they exit the roundabout. Therefore, when designing and implementing roundabouts, authorities should avoid implementing multilane roundabouts before their capacity is needed. If design year traffic volumes indicate the need for a multilane roundabout, but this need isn’t likely for several years, the roundabout can be built as a single‐lane roundabout, and designed to be easily reconstructed with additional lanes in the future when and if traffic volumes increase. In 1 addition, where a roundabout is proposed at an intersection of a major multilane street and a minor street, consideration should be given to building a roundabout with two‐lane approaches on the major street and one‐lane approaches on minor streets. When compared to roundabouts with two lanes at all four legs, this design can significantly reduce complexity for all users, including bicyclists.

MDOT even made a video of an apparently overbuilt roundabout and suggests bicyclists would want to use it. Of course they fail to show bicyclists having to move to the center lane in order to exit at other intersection legs.

Ignoring Bicyclists

The other major roundabout issue is bicyclists as well as pedestrians are often ignored when they are designed and discussed.

We Are Modeshift recently wrote this fine article on this topic.

When roundabouts are placed appropriately, they increase traffic flow and provide motorists with well-documented safety benefits. However, for non-motorized users — bicyclists and pedestrians, and especially those with disabilities — roundabouts present unique challenges to safety and accessibility.

Speaking of safety, a recent survey from a Wayne State/MDOT roundabout study found that 47% of bicyclists and almost 50% of pedestrians found them “very unsafe”. Interestingly enough, 57% of all the survey respondents had purposefully avoided a roundabout.

An example roundabout design that ignores bicyclist and pedestrian safety is on the cover of MDOT’s How to Use a Roundabout brochure (see photo). How are pedestrians supposed to use this facility? There are no sidewalks, even on the bridge. The pedestrian instructions inside the brochure fail to address the roundabout design on its cover. As for bicyclists? They have to cross over a travel lane that becomes a entrance ramp to I-75. Though it’s not shown, there’s another roundabout on the other side of I-75 with the same lack of accommodation. If bicyclists want to avoid this roundabout, there are no sidewalks available.

This is not a Complete Street nor a Complete Roundabout. It’s not something we should continue to build much less highlight.

MDOT’s office of Research and Best Practices shows the same incomplete intersection under the title, “Roundabouts: How to get around a safer intersection.”

Apparently they forgot to add, “So long as you’re in a car.”

 

 

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One Response to “Incomplete Roundabouts”

  1. Dylan Says:

    I know that they seem intimidating but I prefer them to traditional intersections and think that one would go much better at an intersection like MLK/Trumbull/Grand River in Detroit than the current situation where you have to slow and look all ways no matter the light because drivers tend to run them (especially later at night).

    I haven’t ridden on the one you high light but the Portsmouth Traffic Circle (http://en.wikipedia.org/wiki/Portsmouth_Traffic_Circle) in NH is rather large and I did not mind riding through it on my bike at all.

    Why? Because you only have to look for traffic that’s already in the circle before going and then once you’re in there people have to yield for you.

    ON the other hand people out east are much better at yielding for pedestrians and merging one after another to keep traffic flowing.

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