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Roundabouts!

Roundabouts!  Just saying that word in public is a surefire way to illicit a negative response from someone.  Its human nature to fear the unknown, and in this case even the known entity will frighten some away.

 

The facts is, Roundabouts are among the safest options available for accident prone intersections.  They are an intersection design used to reduce congestion, repair poor geometrics, and ultimately to improve intersection safety.  It is an unquestioned fact that roundabouts WILL reduce accident rates as well as the injuries caused by these accidents.  Modern Roundabouts are safer, more efficient, and less costly than any other intersection design.  These are proven facts, not just rhetoric used by roundabout peddlers eager to construct the next one. 

 

The FHWA Office of Safety has identified roundabouts as a Proven Safety Countermeasure because of their unique ability to reduce the types of crashes where people are seriously hurt or killed by 78-82%, when compared to stop controlled or signalized intersections, based on data available from the Federal Highway Administration.  That’s right, an average of 80% serious crash reduction! 

 

“Why the reduction?” some people may ask.  The following chart represents the reduction in conflict points from 32 at a typical intersection to only 8 at a roundabout.  

roundabouts

This combined with vehicle speed reduction from 50 mph to 15 mph through the intersection each contribute to the drastic reduction in accident and injuries.

 

There are certain intersections in Clinton that would benefit from a roundabout.  The most glaring of these are several along Mill Creek Parkway, especially at intersections of 13th Avenue North and 16th Street Northwest.  Roundabouts were discussed at these intersections in 2016 by the City Council, and a recent cluster of accidents at 16th Street Northwest have been a topic of conversation on social media, which have brought the issue to light again this year. 

 

The City Engineering Department has recently analyzed traffic accident data throughout the Mill Creek Parkway corridor, and found these two intersections to far exceed the statewide average of 0.7 crashes per million vehicles entering the intersection.

 

Collision History at 13th Avenue North

 

From January 1, 2012, through June 30, 2017, the intersection of 13th Avenue North and Mill Creek Parkway had a total of 19 reported crashes. Of the 19 crashes, 13 crashes were caused by failure to yield right-of-way or ran STOP sign.    The table below summarizes the reported crashes at the intersection by severity including injuries.  The crash rate of the intersection is 1.03 crashes per million entering vehicles.

 

Injury

Crashes

Fatal

Major Injury

Minor Injuries

Property

Damage

Only

Total

Crashes

Amount of Property Damage

9

0

0

16

10

19

$100,000

 

Collision History at 16th Street Northwest

 

From January 1, 2012, through June 30, 2017, the intersection of 16th Street NW and Mill Creek Parkway had a total of 31 reported crashes. Of the 31 crashes, 22 crashes were caused by failure to yield right-of-way or ran STOP sign.    The table below summarizes the reported crashes at the intersection by severity including injuries.  The crash rate of the intersection is 2.19 crashes per million entering vehicles (MEV). 

 

 

Injury

Crashes

Year

Fatal

Major Injury

Minor Injury

Property

Damage

Only

Total

Amount of Property Damage

23

Total

0

5

15

8

31

$193,700

 

 

Crash Conclusions

 

Without improvements to these intersections, collisions are expected to continue on an increasing trend, due to the expected future development and increased traffic in the area.  Roundabouts are the only proven method to improve the safety of these intersections.  Construction of roundabouts would drastically reduce the amount of high speed collisions and corresponding injuries resulting from these crashes.

 

Compelling Roundabout Facts

 

  1. Overall crash reduction of 72% (FHWA)
  2. Overall injury reduction of 87% (FHWA)
  3. Can be constructed to accommodate large truck traffic
  4. Can be constructed to accommodate future growth to four lanes
  5. Improves overall intersection delay by eliminating stop signs and red lights
  6. Increases awareness and attentiveness of drivers when entering intersections

 

With roundabouts trending nationwide at a near 100% success rate, it may be time for Clinton to join in on the fun.  While not always initially a crowd pleaser, roundabouts will grow on you over time as an experience you sometimes have to drive to believe.  You don’t have to go very far to find success.  The nearby cities of Dubuque, Cedar Rapids, and Prairie Du Chien have recently constructed successful roundabouts. 

 

Conclusions & Recommendations

 

Through discussions with the Iowa DOT, it is our understanding that each would be a great candidate for full funding through the Iowa Traffic Safety Improvement Grant Program. 

 

These projects would include modification of the existing two-way stop control intersection to a single-lane roundabout intersection.  Adding traffic signals is not a good option, as it would not have a guaranteed positive effect on the traffic accidents at the intersection, and would actually decrease the overall delay time of the intersection.  Roundabouts on Mill Creek Parkway will be much more desirable than a corridor of signals for many reasons, including safety concerns, delay issues, and operation and maintenance costs. 

 

Our recommendation would be to apply for the upcoming Iowa DOT traffic safety grant immediately.   The City would very likely receive full funding, given the traffic counts, accident history, and injury history.