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Friday, July 16, 2010

Flashing Yellow Arrows Work Better

Even as early as kindergarten, I remember reciting the basic traffic rules mantra – “Red means ‘stop,’ green means ‘go.’ Now, although many people, myself included, often believe that yellow means step on the gas, I do still remember the often unmentioned addendum to the mantra – “Yellow means ‘proceed with caution.’

However, paying attention to that mantra was why traffic engineers are starting to embrace the use of the flashing yellow turn signal arrows to let drivers know they can make a yielding left turn. Until recently, most intersections that allowed drivers to turn left in the spaces between on-coming traffic used a round green ball signal with a sign that told drivers to turn left on the green ball. That rule made sense, but it didn’t keep the signals consistent. When the signal was green, you couldn’t “go,” you were supposed to “proceed with caution.”

So as St. Louis started to test these signals (three of them on Olive Boulevard in 2006) and now is installing them in locations around the area (currently, there are a number on Route K in St. Charles county, five more on Olive Boulevard, and a number on Lindbergh Boulevard), the concept made sense to me.

I have seen some comments from local drivers during the introduction of the flashing yellow arrows. They seemed to fall into two categories. 1) people seem to be confused by these signals, and 2) the change is simply because someone wanted to justify their continued existence and adjusted these signals just for the sake of change.

The first part may be somewhat true – as you introduce a new element to the driver, some of them can potentially misinterpret what the flashing yellow arrow means. The second is flat-out wrong. The Federal Highway Administration sponsored a study that showed that the signals were safer, and that more people understood what the flashing yellow arrow meant.
Basically it breaks down this way – the green ball signal with the yield sign is equal to the flashing yellow arrow. The flashing arrow is more intuitive, is safer, and is more consistent with what we teach our youth about traffic signals.

You can find out more information on the flashing yellow arrows at our website. You can also access the Federal Study from that site. We also have a video showing how to drive through a flashing yellow arrow on YouTube.

Andrew Gates
MoDOT Community Relations


Dan said...

Being as involved as I am with signals, etc. When MODOT deployed the FYAs on Olive during the study, I was curious about how it would do. I've watched many times as I drive by the 3 intersections and personally have never seen any -major- confusion. Usually either people treating it like a normal yellow trap intersection (out past the stop bar), or yielding properly. I am disappointed that the sign had to resort to telling people to yield, instead of just the "Left Turn Signal". You'd think yielding to Flashing Yellow, was common sense? Oh well. I've modeled my FYA display after those intersections (I'm a signal collector and fan). So I always keep my eyes out for any new stuff you guys do.

MoDOT- Andrew Gates said...

Thanks, Dan -- it would have been nice not to have to put the sign out, but it also helps eliminate any confusion -- especially as we are transitioning to the new signal.

Andrew Gates