October 26


Traffic Calming Analysis – Real World Example

By Mike Spack

October 26, 2012

Traffic Calming Speed Humps Pocket Radar Inexpensive Radar Gun

Paul Oehme (Chanhassen, MN City Engineer) asked me to look at Pleasant View Road (below) for potential traffic calming and then come to a meeting with a couple of concerned residents who live on the road.  

The city has it designated as a collector and it's the only east-west road in the area that goes between County Road 101 and Powers Boulevard – each minor arterials.  The area has three lakes that prevent alternative routes.  

Pleasant View is a twisty, rolly, 24 foot wide, very scenic road.  There are a lot of trees and a drop to Lotus Lake on the south.  No trails or sidewalks and public right-of-way is only 30 feet wide in certain spots.  The posted speed is 25 mph and it has about 3,000 vehicles per day using it.

Paul sent me speed data they collected.  The 85th percentile speed is 31 mph in a curvy portion east of Fox Path, which surprised me.  The city has extra police patrols along the corridor several times a day.  Also – no reported crashes in the last five years.

The residents were asking what could physically be done to the road.  My answer – not much.  The location of houses, the topography, and constricted right-of-way make it a poor candidate to upgrade the road design to a more typical collector road (and the residents wouldn't want this anyway).  To me it seemed like sidewalks would improve the road for bikes/peds, but the residents didn't seem excited about that even though they kept talking about the safety of there family members on the road.  

I shared the different types of calming methods available (www.TrafficCalming.org is the best resource out there).  We all agreed the speeds were the issue, not the amount of traffic.  

Speed humps would be the most effective measure to reduce the speeds.  But I'm not excited about speed humps in this scenario – the curves and hills make them a drainage/safety problem in our icy winters and it would be expensive to line this long corridor with them.  Speed humps need to be spaced every few hundred feet, otherwise studies show motorists gun it between the humps to try to make up time.

My conclusion – the other two E's of traffic calming need to be implemented (Enforcement and Education in addition to the Engineering).  There isn't a clear engineering answer and its a marginal issue statistically.  

Enforcement – The police already do increased patrolling, but talked about doing more speed enforcement.

Education – I offered the idea that the neighbors could get an inexpensive radar gun, clock the speeders, write down the license plates, and then have the city send a nice reminder letter ("your vehicle was clocked doing xx mph at xx, on xx.  This is a friendly reminder the speed limit is only 25 mph.").  The city was open to this, but the residents didn't seem to want to put in the time.  

That would be interesting data to have because the DMV records would give the home addresses for the vehicles.  My experience is speeding problems are usually caused by local residents, not out of town folks.  As you can see from the map, this is not an attractive cut-through route.  The speed issues are very likely residents from the adjacent subdivisions or even the residents on one end of the road.


View Larger Map

  • Safety of family members doing what on the road? From people fronting on the roadway, or those walking or biking along it?
    For passive measures I would think about a narrowing to 10′ lanes with wide edge lines, at least in the straightaways. 25 MPH is a tough taget to hit on a road like that I think, 31 MPH 85% and no crashes isn’t indicative of a huge problem.
    There’s no Streetview of the road so I can’t see what sidewalks would be like on it. I think that’s a big can of worms that the majority of landowners probably won’t want. Not only property aquisition, landscaping disruption, and how some neighborhoods dislike sidewalks for giving access to undesirable elements. I don’t think it would get much if any speed reduction either.

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    Mike Spack

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