September 20


I'm helping a couple of young traffic engineers at a local consulting firm until the firm gets through their current surge of work.  I just reviewed a well written traffic assessment memo.  I did find a little teaching moment though.

The purpose of the memo was to document the existing conditions in the study area (capacity analysis, access spacing, and crashes).  The next step in the process will be alternatives design/analyses, which will lead to recommendations and then to final design.

The young engineer wrote that the current intersections were unacceptable because they violated access spacing standards.  He also wrote about all of the intersections operating acceptably at Level of Service C or better and discussed the mixed bag of crash history (two intersections had high crash rates, three didn't).  

I softened the access spacing language to "the intersections do not meet current access spacing guidelines."  I believe the situation was certainly in the gray area, not the black and white land of needing to realign a whole road and close business driveways.  A change that big is something that needs to be hashed out with further analyses and then ultimately through public meetings with politicians.  The word "unacceptable" seems too strong and was a premature conclusion.

This reminded me of a turning point in my engineering judgment.  It came within a few weeks of me being on the job as the traffic engineer for the City of Maple Grove.  I had already done three years in consulting firms and had a handle on the technical parts of being a traffic engineer.

The city engineer, Ken, came into my cube and told me a council member had requested all way stop signs be installed in the back of her subdivision because her cat was run over and she didn't want that tragedy to happen to someone else.  I piously started quoting the warrants for installing all way stop sign control from the Manual on Uniform Traffic Control Devices.

I was going to need to get traffic counts and do a crash study, but based on looking at the layout of the subdivision I was certain the intersection wouldn't meet warrants and therefore we shouldn't install the stop signs.  Ken let me ramble on.  When I was done, he said that was all fine but asked what was the worst thing that would happen if we did install the stop signs.

We already had unwarranted stop signs in the city.  Philosophically, unwarranted stop signs change the universe by slightly degrading respect for stop signs throughout the world.  At busier intersections, they can also lead to safety problems because people start to blow the stop signs because there's usually no reason to stop.  But really, I didn't expect anything bad to happen at this particular intersection if it had all way stop sign control.

Ken said they hired me to make these decisions and was delegating this to me.  He told me to go through whatever process I thought necessary and make a recommendation I could live with.  And then he asked me if I liked my new job at Maple Grove.  I told him I was very happy, why?  He explained that we ultimately work for the city council members and they have the power to have us fired.  They also make funding decisions, so it's wise to be on their good side.

I thought about the situation for about five minutes and decided to write a quick consent agenda motion for the next council meeting authorizing the installation of all way stop signs at the intersection (it limits tort liability if the city council directs the traffic control installation).  Then we installed the stop signs.

Bad karma – maybe.  Bad engineering – maybe.  Built good will with the bosses – yes.  Kept my job – yes.  

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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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