Re: Flashing Yellow Left Turn Arrow in Colorado

Steve Riner wrote:
Colorado DOT has installed its first flashing yellow left turn signal,
or I guess it should be described as a part-time protected/permissive,
part-time protected only left turn. (This is the first CDOT
installation, but there is currently a city-installed installation in
Boulder.) The signal at U.S. 50 and Fortino/Morris in Pueblo was
upgraded to this experimental format. U.S. 50 is an extremely busy
(ADT = 50,000), four to six-lane route across the north side of Pueblo.
Most of the signals along here have protected/permissive left turn
signals, but making a left turn without the green arrow is almost
suicidal much of the day. CDOT determined that over half the accidents
at these intersections were left-turn related.

The signal was installed this week by replacing the former five-light
assembly with a vertical, four-light signal head on the crossarm and
the opposite left corner. Different lights are used for the flashing
yellow arrow and the steady yellow arrow. So far, I've only driven by
the intersection during peak traffic times when the signal operates in
protected-only mode. At this point, I'm not sure when the signal
goes into the dual mode, whether it's at any time during the day on a
weekday.

Given the volume of traffic, I would have opted for protected-only
phasing, but I can understand that during periods of low traffic volume
at night or on weekends, traffic could be waiting unnecessarily at the
intersection. Another concern I have is the use of flashing yellow for
the turn arrow as opposed to red, mainly because there are a number of
signals around Pueblo that go into yellow-red flashing mode at night or
after school hours. Some drivers may equate a flashing yellow arrow
the same as a flashing solid yellow light - "I have the right of
way." There is no sign on the signal currently, but a sign might be
useful, such as "NO TURN ON <red arrow> / YIELD ON FLASHING <yellow
arrow>."

The City of Pueblo has a CDOT brochure describing the signal's
operation on its web site:
http://pueblo.us/documents/Transportation/FlashingYellowArrowFlyer.pdf

Steve Riner
Pueblo West CO

Explore New Mexico and Minnesota highways: http://www.steve.riner.com

Well, this sucks, IMO.

Green ball means the same thing. Introducing a redundant signal for the
same movement traditionally allowed by another signal is not only
superfluous but potentially confusing. It would be reasonable for a
driver to assume flashing yellow means something he's never even heard
of and he wouldn't know how to respond to it.

Substituting a yellow flashing arrow for the green ball doesn't make it
any safer to turn and doesn't increase the driver's ability to perceive
whether there's a safe gap in oncomign traffic.

.