July 7


New Report – Safety Record of Roundabouts in Minnesota

By Mike Spack

July 7, 2015

bycyclists, COUNTcam, COUNTcloud, Roundabout, Safety, tdi, traffic data inc
Photo Source:  Washington County, MN
Photo Source: Washington County, MN

Roundabouts keep getting good press in Minnesota.  Check out this positive story from Minnesota Public Radio.  We have about 140 roundabouts built in the state with 40 more in the works.

I was excited to see these statistics in the report:

“In December, MnDOT released its first comprehensive traffic safety study on roundabouts in Minnesota. It compared crash data for 24 locations before and after the roundabouts went in. Overall, crashes dropped 30 percent. Crashes involving injuries dropped by 65 percent and the most severe crashes dropped 82 percent.”

Click the link to view the MnDOT study:  A Study of the Traffic Safety at Single Lane Roundabouts in Minnesota 

(Special thanks to Derek  Leuer, PE the author at MnDOT who graciously shared this with me even though it hasn’t been released online yet!)

On a side note –

Conducting turning movement counts at a roundabout with people on the ground is very difficult to nearly impossible.  We’ve counted about a dozen roundabouts through Traffic Data Inc and COUNTcloud this year.  It’s feasible now that we are using COUNTcam video camera technology.

I even sat down last month to do a little counting from a video at a busy multi-lane roundabout.  It reinforced my appreciation for our data collection staff!  I had a hard time keeping up with doing one leg at a time on 2x speed.

If you’re interested in learning more about roundabouts, you might also want to check out these posts:


  • Thanks for sharing, Mike!
    Interesting report and methodology! Building roundabouts at certain intersections is a good measure to increase road safety.
    For a proper before and after road safety evaluation though, the regression-to-mean effect has to be considered.
    We just presented a paper at the UK Annual Transport Practitioners’ Meeting (https://www.ptrc-training.co.uk/Events/TPM2015.aspx) called “Identifying Collision Hotspots using Time Series Analysis and Accounting for Regression to Mean”. Before and after analysis of the crash situation should use this or a similar approach to make a scientifically sound claims on crash reductions numbers/rates.
    We are currently implementing this methodology in our road safety analysis tool PTV Visum Safety.
    [Full disclosure: I work for PTV Group]

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    Mike Spack

    My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

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