Those left-turn arrows going in at 160 new Los Angeles intersections will mostly be of the kind that switch to a full green light—"green ball" to traffic engineers—rather than a red arrow that makes left-turners wait for no reason. Sean Skehan of the city Department of Transportation told me this week that green-fading-to-green is the preferred way in L.A., since it moves traffic more efficiently. They typically use red arrows only at corners with more than one left-turn lane or a history of accidents. I wish more cities—are you listening, Santa Monica?—would be less crazy with the red arrows.

Many of the new green arrows will also be hooked up to sensors that only switch on the arrow if more than two cars are waiting to turn. Only invoking the arrows when needed helps reduce the traffic disruption that they cause at intersections. I talked to Skehan at a ceremony to unveil smart traffic signals along the Reagan Freeway in Northridge.

Even smarter signals?: Beaverton, Oregon and some other cities are experimenting with flashing yellow arrows to remind drivers to be alert when making left turns. I have noticed that when a left arrow fades to normal green, some drivers seem flummoxed and think they need to wait for another left arrow to come along. (Fullerton in Orange County has gone to the blinking yellows, I'm told.)

Blogged traffic: Curbed LA reported on the new arrows, and blogging.la has had some posts recently about the "compact" parking spaces that developers have been squeezing in to garages and lots.

* After the jump: Flashing yellow arrows are in Pasadena too, and some drivers just don't get it...

Jeff emails:

Kevin-

Pasadena, like Beaverton, just started installing signals with
flashing yellow left-turn arrows in the past few months (on Arroyo
Pkwy) and I've noticed a different problem than what you describe:
most drivers, especially during rush hour, when the left-turn light
changes from green to flashing-yellow do not proceed to turn at all,
even when the coast is clear and it is safe to do so. Drivers seem to
think that because the light is not green, they cannot go. They treat
the flashing yellow lights like solid red lights!!!

These new signals, oddly, have weird red flags sticking out of them. Why?

Cities that install these lights need a to include a public
information component to educate drivers on how to intepret these
signals. Otherwise, as in Pasadena, the signals just add to the time
and frustration of driving!

Hope all is well. Keep up the great work on your site.

Robert thinks they're a boon:

Hi Kevin,

Pasadena has the blinking yellow arrows on the Arroyo Pkwy. When a Gold Line Train is approaching (it runs parallel to the Arroyo Pkwy. half a block to the west), the left arrow flashes yellow for westbound traffic on cross streets, while the eastbound crossing traffic sees a green ball. That way, eastbound cars can move off the Gold Line track while allowing westbound drivers wanting to going south on Arroyo to make their turn when the eastbound cars clear.

Before the blinking yellow arrows, the westbound drivers waiting to turn south had to sit there under the red ball for all westbound traffic, as only the eastbound got a green while the Gold Line trains approached. It's definitely lowered my frustration level with the Gold Line as I drive out of Pasadena in the mornings.