It means that traffic turning in the direction the arrow points may turn, but must yield the right-of-way to conflicting traffic
No.
- For the left turning driver, the flashing yellow arrow and the circular green have the same meaning.
- But their meanings are very different for drivers who are not turning left.
- Those drivers must look at other signal faces instead of at the flashing yellow arrow.
This lets the signal completely separate control of the permissive left turn from control of the straight-ahead traffic.
No, it is not. That is not why the flashing yellow arrow is used.
Flashing yellow arrow provides an indication that can not otherwise be displayed. This indication lets drivers make permissive turns while the straight-ahead traffic is stopped with a circular red. The circular green can't possibly do this.
This new indication provides the following advantages:
- It prevents a hazard called yellow trap (caused by the circular green).
- It gives traffic engineers more choices of light sequences the signal can use.
- These sequences include a lead-lag sequence with permissive turns.
- The lead-lag signal allows traffic engineers to progress green lights on more two-way streets.
More permissive turns and more progression mean saving gasoline.
There are several possible reasons:
- As a layman in the field of traffic control, he probably does not understand either yellow trap or signal progression.
- He may have read the report on driver understanding of the flashing yellow arrow. Since a new indication was needed, it had to be tested for driver understanding, to prevent unexpected hazards. But this was not the intended purpose of the flashing yellow arrow.
- He might have been asked a question he didn't know the answer to. So, instead of saying, "I don't know," he guessed.
The flashing yellow arrow can allow the permissive turn to be made while the straight ahead signals are red. The circular green can't do that, because it also tells other movements to go.
For the following reasons:
- To prevent the hazard of yellow trap.
- To have a longer permissive turning period in the signal cycle.
- To have more signal sequences available without the hazard of yellow trap.
- To be able to put signal progression on more two-way streets.
- To make traffic use less gasoline.
Yellow trap occurs when all of these come together at the same signal:
- Left turns are allowed on the circular green on the affected street.
- The signals for both directions of the same street are showing circular green.
- The signals in one direction turn yellow, while the signals in the other direction remain green.
| 1 Circular Greens | 2 Signal Changes | 3 Yellow Trap |
|---|---|---|
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The driver getting the yellow light thinks both directions changed to yellow, and that the traffic coming from the other way will stop. He turns across live traffic that still has a green light. If he doesn't turn, he might be trapped in the intersection with a red light.
Yes and no. The problem is that each driver thinks a different law applies at the moment:
- The driver receiving the yellow light thinks both directions have a yellow light. The law he is concerned with is getting out of the intersection before the red light. And he expects the driver coming from the other direction to stop for a yellow light.
- The driver with the green light does not know the signal has changed. He still sees a green light. The law he is concerned with is that turning drivers must yield to oncoming straight ahead drivers.
The problem is that each driver expects the other driver to stop. When the other driver does not stop as expected, the accident occurs.
Signal progression is the timing of traffic signals relative to each other, so the lights on the progressed street turn green as the driver comes to them. Progression is beneficial, because drivers don't have to stop as often for red lights. This saves gasoline.
That works only when the street is an isolated one-way street.
The problem with doing that on a two-way street is that any timings set that way are wrong for traffic going the other way on the street. A complicated procedure is needed to cause progression to occur in both directions on a two-way street. Even with a one-way street, progression on the cross streets must also be considered.
One tool that can make progression work on more two-way streets is the lead-lag signal sequence. But without the flashing yellow arrow, the lead-lag sequence must have left turns stopped at red arrows, instead of allowing permissive turns through gaps in oncoming traffic.
A leading left turn arrow occurs before the oncoming traffic gets its circular green.
A lagging left turn arrow occurs after the oncoming traffic gets its circular green.
The lead-lag sequence (using flashing yellow arrows) operates in the following order:
| 1 Leading | 2 Thru | 3 Lagging | 4 Cross street |
|---|---|---|---|
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|
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The orange dashed arrows show left turns made using flashing yellow arrows.
If flashing yellow arrows are not used, the orange arrows would have to be deleted from diagrams 1, 2, and 3 to prevent yellow trap. Those turns would be stopped with red arrows, instead of being permissive. (In this case, the orange arrows in diagram 4 would show left turns made on the cross street circular green.)
The lead-lag sequence allows the traffic engineer to adjust the signal to meet the arrival times of the platoons of cars coming from each direction. In this case, the timing plan has cars arriving from the left coming earlier than the cars that arrive from the right.
There are several different reasons that different sequences are needed:
- The alignment of the intersection might not allow simultaneous left turns in both directions.
- If one or more approaches don't have exclusive left turn lanes, then the left turn signals facing them can't be green when the circular signals are red.
- Widely differing traffic demands on different approaches might demand another sequence.
- Different sequences are needed at different intersections in a progression system to optimize progression. This saves gasoline.
Why does the flashing yellow arrow face require two yellow arrows? Why not just flash the one used for clearance?
The Manual of Uniform Traffic Control Devices requires that the yellow arrow used for clearance must be above or to the left of the yellow arrow used for the flashing yellow arrow permissive turn. This is so the arrow changes sections in the signal face when the signal changes, in the same way that the lighted section moves when the circular green changes to circular yellow.
Look at the model at right. Notice how the arrow moves when the signal changes. It is much more visible than just stopping the flashing of the arrow.
It is operating correctly. This is the part of the sequence that prevents yellow trap and provides all of the other advantages.
The flashing yellow arrow flashes at all times when the oncoming circular green is lit. This is the only way to remove yellow trap from permissive turns.
This is the wrong way to install a flashing yellow arrow. It causes the same yellow trap the circular green causes.
In order for the flashing yellow arrow to prevent yellow trap, the flashing yellow arrow must be tied to the oncoming circular green, not the circular green facing the same way the flashing yellow arrow faces. The circular green facing the same way has the wrong timing, causing yellow trap.
NO!!! That is dangerous and illegal.
When a flashing yellow arrow face is installed, it is the only face controlling left turns. The circular indications often show indications that are wrong for the left turn driver to obey.
The entire purpose of the flashing yellow arrow is to separate the permissive turn from the circular green.
If you can't learn this simple addition to traffic signals, or drive anywhere signal sequences are different, you do not belong on the road.
It is broke. It has been broken for at least 80 years.
Yellow trap has been around as long as left turn signals have existed. And up until now, there has been no standardized fix that worked:
- The problem was not recognized until the mid 1950s. Officials and police assumed the accidents caused by yellow trap were caused by driver inattention, failure to yield, or someone in too much of a hurry.
- The original "fix" was to avoid lagging left turns. This is why many city signal systems are inefficient.
- Another "fix" was to prohibit the left turn from the direction opposite to the lagging left turn - inconvenient for other drivers.
- Indiana used a steady yellow arrow for a permissive turn in the 1950s. The arrow went out for a clearance period.
- Special circuitry had to be installed in most signal controllers to keep them from skipping phases into a yellow trap.
- The first real development was the flashing circular red used for permissive turns in Michigan. But it required each turning vehicle to stop. Maryland later used the same signal.
- Delaware, Maryland, and California used a flashing red arrow instead. It still required each turning vehicle to stop.
- Washington (state) adopted a flashing circular yellow in the position normally occupied by the circular green. It was very effective.
- In the late 1980s, Dallas Texas started using what is called "Dallas Phasing" to eliminate yellow trap. It showed the opposing circular green and yellow to left turning drivers, instead of the adjacent ones. Visibility-limited signals were used. But it confused drivers who saw their own left turn signal with a circular green, while the other signals had circular red. This, plus the fact that straight ahead drivers thought the circular green was burned out, caused many false maintenance calls.
- Nevada first experimented with the current flashing yellow arrow signal face in the 1990s.
- After a 10 year study period, the flashing yellow arrow signal was adopted into the US Department of Transportation's Manual of Uniform Traffic Control Devices (MUTCD) on December 12, 2009.
Yes:
- Some states used to define the flashing yellow arrow as the way to display a privileged movement when the signals are on night flash. People from those states got into accidents when they saw flashing yellow arrows while driving in other states.
- One flashing yellow arrow installation in Oregon was converted to exclusively-protected left turns, due to unusual intersection geometry causing accidents.
Yes. Flashing yellow arrows can not be used where any of the following conditions exist:
- A single approach lane
- Any approach where a lane is shared between the controlled turn and other traffic movements
- Where more than one permissive turn would turn into the same intersection leg
- Where the flashing yellow arrow movement would cross more than one other movement
- Where conflicts develop in multilane left turns
Fewer than ten states have not yet approved the flashing yellow arrow.
There are several factors:
- The 4-light flashing yellow arrow face costs less than the 5-light traditional shared left turn face.
- In most cases, the signal faces that are taken down can be reconfigured and used again. The lamp sections come apart for this purpose.
- The flashing yellow arrow face can not be used as one of the two required faces for straight ahead traffic.
- In a signal being converted from a 5-light shared signal, two more signal circuits per approach are needed. This might mean replacing cables.
- An older signal controller and/or conflict monitor may have to be replaced to get the ability to operate flashing yellow arrows.
- This is a job for a trained engineer, not a local politician, police chief, or electrical contractor.
A new installation where no signal existed before should cost less than the equivalent signal with a shared 5-light left turn display.
The main cost of converting an old signal is the labor. It would be equivalent to the cost of adding or removing a left turn phase.
Labor is also the main cost of a sign. A new stop sign ready to be installed costs under $50. After installation, the cost is over $200.
Only if it is carefully installed, with particular attention paid to the following:
- It must be installed correctly. If it is installed wrong, a flashing yellow arrow can cause yellow trap as badly as a circular green.
- Attention must be given to second yellow trap. This is where a right turn overlap can cause yellow trap for a permissive turn.
- Pre-emptions for fire, police, ambulance, railroad, drawbridge, queue discharge, or other special circumstances must be specially designed to prevent yellow trap. A common mistake is to value government workers more than the lives of others.
- Unusual intersection geometry, including offset legs, skewed approaches, and more than 4 legs, must be specially designed.
- The 4-arrow flashing yellow arrow face.
- A 3-arrow version with a dual color indication section that displays both a steady green arrow and a flashing yellow arrow.
- A 3-arrow version with no green arrow. This is used where yellow trap must be prevented, but the approach has no left turn phase.
- A 3-arrow face without a flashing yellow arrow can be used for an exclusively protected turn or a flashing red arrow face.
- The 5-light 2-arrow signal may be used where it doesn't cause yellow trap. It must be used where a shared left and straight lane exists.
- A 4-light 1-arrow face can be used for split phasing (each leg has its own green).
- Where no left turn phase exists and no yellow trap is possible, a 3-light no-arrow signal may be used for permissive left turns.
The federal government has already approved it in the 2009 MUTCD, as the preferred left turn signal where it can be applied.
If you don't like it, you don't really understand the benefits of having it. It appears to be the left turn signal of the future. The safety record proves that.
You are in the minority, and will not be able to stop it.