The Mother-in-Law Test

Last summer, we took a beach trip to Ocean Isle, North Carolina.  One afternoon I ventured out with my mother-in-law, Sharon, to get some fresh blueberries.  On the drive back to the beach from Holden Brothers Farm Market I saw a flashing yellow arrow for a left turn at a signalized intersection ahead.  It was the middle of the day and the road was mostly deserted.  I slowed the car and asked Sharon for her thoughts on the signal indication, “Well, it’s yellow so I have the right away, but it’s flashing so it means it’s going to end soon and I should hurry up and turn left.” 

Not even close.  Thankfully, I was the one driving. 

Flashing yellow arrows were recently introduced for permissive left turn movements at signalized intersections.  However, unlike green arrows, the left turning vehicle does not have the right-of-way and instead has to wait for a gap in oncoming traffic before turning left.    

It probably appears at this point that I’m picking on my mother-in-law; I’m not.  In fact, the opposite is true.  Sharon is well-educated, a retired high school teacher with an advanced degree in English.  I value her insight on this topic (and, she reads this blog).   

I started occasionally asking Sharon for her perceptions on traffic control devices over ten years ago.  We were walking in downtown Portland, Oregon.  As we crossed at a signalized intersection Sharon said, “I’ve been meaning to ask you, what does the flashing hand mean on the pedestrian signal?”   I had just finished two national studies on pedestrian countdown signals that included on-street surveys of pedestrians to determine their understanding of traditional pedestrian signals compared to countdown signals.  Sharon’s understanding of the traditional pedestrian signal indication mirrored what I found in my surveys.  Pedestrians understood the WALK indication and the steady DON’T WALK of the traditional pedestrian signal, but didn’t understand the flashing DON’T WALK that is displayed between the two.  The newly introduced pedestrian countdown signals provided a message that was more easily understood.    

Sharon has now become my test case for determining if a traffic control device or other transportation practice makes sense to an educated driver; I call this the mother-in-law test.  I don’t ask my husband because he has spent the last fifteen years listening to me talk about highway safety and his perception would reflect that.  (Similarly, I know enough about finance to be dangerous.)  I find that Sharon represents the understanding of an average, educated driver, living outside of a major metropolitan area like DC, New York, or LA. 

Throughout time, transportation engineers have designed some traffic control devices and configurations that make sense to other engineers, but not necessarily to the driving public.  Although most designs have undergone testing before wide-scale implementation, some slip through the cracks.  In discussing this topic with others, several notable examples have emerged including ramp metering signs, the graphical lane ends sign, milling signs, or the sign pictured at the top of this post.  Although traffic engineers and Bon Jovi fans will recognize this sign as indicating slippery when wet, some drivers perceive this as indicating there are curves ahead. 

So how do we avoid designs that are confusing to the average driver?  I think a good starting point would be to stop asking our fellow traffic engineers, drivers in the DC area, or spouses/significant others if the designs make sense.  Instead, we need to start asking our mothers-in-law. 

Please use the comment box to share other traffic control devices or configurations that are misunderstood.  I’ll pass them on to Sharon for her thoughts.