I love the promotional material that typically accompanies flashing yellow arrow installations (or at least did for a while). They act like it's the first type of signal to ever allow discretionary left turns.
Now it may be true that many of these have replaced fully protected left turns, but if they were looking to alleviate congestion, there have been ways to allow permissive lefts for as long as traffic lights have existed, and ways that included a protected phase for at least 50 years.
The reason why the flashing yellow arrow became necessary was a problem with five-section permissive heads called "yellow trap" that happened in configurations with a lead-lag left turn phase. Effectively, the direction that got the leading phase would have its green ball turn yellow, which would prompt those making a permissive left to make a left turn (as is normal on a yellow). However, oncoming traffic still had a green signal; the left-turners direction received a red signal because to allow the oncoming direction's left turn to receive a yellow signal. This would cause people to pull into oncoming traffic to make a left turn, with the assumption the traffic was stopped, only to be hit by cars that were given a green signal.
Flashing yellow arrow signals make lead-lag left turns safer, which is great, because lead-lag left turns are (as far as I know) the most efficient configuration. I don't know why we don't see more lead-lag left turn configurations though.
You also have to consider that flashing yellow arrow signals can serve as protected only signals for certain times of day, and can allow permissive left turns when the thru direction has a stop signal. These aren't possible on the traditional inline-five or doghouse, unless a very specific signal setup is laid out.
Pretty much, they're marketing the FYA so hard because people need to know how it works to take advantage of it. I personally like the inline five and doghouse signals, but the FYA just... does things they can't.
TLDR: The FYA signal isn't the first discretionary left turn device... it is an improvement on what we had that requires a little bit of education to understand.
I think I may not have fully explained my thoughts.
I understand why the FYA was created, it's certainly much more flexible in its deployment and operation than the traditional green ball setup (either fully permissive or protected-permissive using a four or five section signal with green and yellow arrows). But it's not a requirement for permissive left turns to "exist", per se.
For example, look at the tweet. The only point they make is that the flashing yellow arrow "alleviates traffic + queue time by allowing vehicles to turn when there is no traffic in the opposing direction". While that's true, if that was their only goal, they could have simply removed the old protected-only left turn signal heads that did not permit discretionary left turns, allowing for traffic turning left to simply proceed
when safe at the same time as through traffic. If necessary, the left turn signals could have been replaced with four or five section left turn signals (aka, a "doghouse" or "tower") that would have also allowed for a protected phase in addition to the permissive phase.
I'm not trying to be pedantic here, I'm just trying to say that FYAs don't really bring anything new to the table unless you are looking for more complex setups (time of day phasing, free lefts during an oncoming green arrow, LPIs, etc). If the expressed purpose was simply to allow traffic to turn through gaps, well, they could have fixed that issue a long time ago.
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Topic: Has the flashing yellow left turn signal made it to your state? (Read 469779 times)