Flashing yellow arrows

Ah, but the committee has justified its existance!

The real problem is that most people expect the green lights in both directions to end at the same time. They think opposing traffic is going to stop at the same time. Most signals do this. But then they come to a signal that doesn’t always do this.

And the way they allow intersections to be overloaded, most people turn on the yellow at most intersections, because it is the only way they can actually make the turn.

Another problem is if there is a small gap in the opposing traffic going straight. Then there is no visible indication of whether the traffic following the gap is slowing down to stop for a yellow light, or still has a green, because they haven’t begun to brake yet. You can’t assume a street full of cars, because yellow-trap usually occurs at night, when one street is totally empty (and the green lights for it are skipped).

When I encounter collisions caused by yellow trap, they are usually at night, when the signal is skipping unused phases (green lights), and the resulting sequence is out of the usual order. Most of the traffic signal equipment allows such phase skipping. It takes special equipment and programming to prevent certain resulting sequences from occurring.

The real issue is that the permissive turn is forced to end at the WRONG TIME in the signal cycle when a circular green is used to indicate a permissive turn. This is because the permissive turn is wrongly tied to the end of the straight-ahead green, because the same circular green indication is used for both. The correct time to end a permissive turn is when the OPPOSING straight ahead green light ends.

“Then there is no visible indication of whether the traffic following the gap is slowing down to stop for a yellow light, or still has a green.”

What are you talking about? I have one for you; the opposing traffic SLOWING DOWN. Are you saying that drivers should not be judging the speed, and changing speed, of the opposing vehicles?

If there is a small gap in traffic, the opposing cars are too far from the intersection to have started slowing down yet (if the opposing light is yellow or red), but they are too close to the intersection for the left turn to be made through the gap (if the opposing light is still green).

The driver in the case above is expected to make the decision based on information he does not have.

The correct implementation of the flashing yellow arrow gives the driver the information he needs:

  • If the flashing yellow arrow is still flashing, the opposing signal is still green, no matter what the adjacent visible circular indication the left-turning driver can see has changed to.

  • If the flashing yellow arrow changed to steady yellow clearance, followed by a red arrow, the opposing signal has also changed to yellow, and the oncoming traffic WILL stop for a red.

What your first paragraph is describing is a malfunctioning traffic signal. Adding another arrow won;t fix that.

In my area busy intersections simply have left turn arrows stay red when the opposing light is green and that turn green to allow left turns typically while the opposing light is still red and before it turns green again. It gives safe left turn opportunities.

While I know that in truth taffic laws and signals are regulated by state statutes and vary some, I still think this yellow trap setup is not a good solution.

The point is the ability to end the permissive turn at the correct (safe) time, not the incorrect (unsafe) time forced by the use of the circular green to control both left and straight ahead traffic with one indication.

If the circular green on one approach ends early, the permissive turn for that approach MUST be allowed to continue until the circular green for traffic going the other way ends. Otherwise, yellow trap occurs.

The yellow arrow can keep flashing until the correct time to end it. The circular green indication can’t be displayed until the correct time to end the permissive turn when the straight ahead traffic must be stopped earlier.

Alternately, we need to be able to show a circular green for left turns, while showing a red for straight ahead traffic on the same approach. That would be even more confusing. The Dallas display does this, by hiding the extra circular green from the straight ahead traffic with louvers.

The real problem is using circular green for two different indications that must end at different times. We need to remove the permissive left turn from the meaning of the circular green, and create a new indication for it. This is needed, so the permissive turn can be started and stopped at the correct times in the cycle, not the incorrect times dictated by the use of the circular green for this purpose.

More states are being added every day. Utah and Delaware are on the growing list, and New Jersey is thinking about it.

This change is already coming. The final approval for it is in the hands of the federal Department of Transportation, and all of the recommendations are positive. It gets rid of a problem we have had since green arrows were first used for left turn signals.

What your first paragraph is describing is a malfunctioning traffic signal. Adding another arrow won;t fix that.

It is not malfunctioning. It is being misused, because the traffic laws are wrong. The use of circular green for both straight ahead traffic AND permissive left turns IS the problem. This is now being changed.

In my area busy intersections simply have left turn arrows stay red when the opposing light is green and that turn green to allow left turns typically while the opposing light is still red and before it turns green again. It gives safe left turn opportunities.

Having the left turn signals stay red is the safest, but it is not energy-efficient, and it can’t move as much traffic. But note that signals do not cause yellow trap when used in this way. They can skip unused greens without causing any hazard when left turns are not allowed on a circular green.

In order for yellow trap to occur, left turns must be allowed to turn on a circular green. This can happen three ways:

  • The 5-section “doghouse” or inline left turn signals are used.

  • One approach has no left turn signal, while the other approach has one, no matter what type.

  • Preemption for emergency vehicles, a railroad, or a drawbridge turns the light red for three directions and green for one direction, whether or not there are any left turn signals.

Most jurisdictions, most politicians, and the EPA, prefer that left turns also be allowed to filter through oncoming traffic that has a circular green. So we have the “doghouse” or inline 5-light signal that controls both straight ahead and left turn traffic. This is where the yellow trap comes from. The circular green is used for the permissive turn, AND for the straight ahead movements. But a standard signal controller has to be modified to eliminate the yellow trap hazard that results if some unused green lights are skipped.

While I know that in truth taffic laws and signals are regulated by state statutes and vary some, I still think this yellow trap setup is not a good solution.

Yellow trap is never a good idea.

The purpose of the flashing yellow arrows is to ABOLISH yellow trap. They assure that the permissive turn ends at the correct time, NOT at the time dictated by the end of the circular green for straight ahead traffic.

Troubleshooter, you must have had a hand in the solution of this “yellow trap” problem, right? No one else would be arguing that this is a better solution then driver training and watching the road. Honestly, your entire argument is people aren’t obeying the current laws and traffic safety implements so lets make new ones.

No. In fact, I just found out about it last year. This research has been going on for 6 years. I like it, because it removes a hazard I have been endangered by too many times.

I don’t fall for the shortened yellow (I fell for it the first time it happened to me, in 1973, but I avoided the wreck). But if I am the straight-ahead driver, I have NO IDEA that anything is wrong until a left-turning driver going the other way turns in front of me. Then I have to jam on the brakes to keep from hitting him.

The original solution I favored was to prevent phase skipping with a dummy all-red phase, to keep the yellow trap from happening. But it doesn’t work for progression. Then I found out about Dallas Phasing, and it was better than anything else, but confusing. Now the flashing yellow arrow seems to be the real solution to this.

I originally tried to respond to a rant by one of the tappet brothers, but the thread was closed.

This is NOT a matter of driver training, because it takes very careful inspection to detect the yellow trap before it is too late. It is a rare event, and unless you are specifically looking for it, it sneaks up and bites you.

You have to look for the following to detect the onset of yellow trap:

  • No cars at all waiting on the side street (assuming a signal where the left turns normally go before the oncoming straight ahead green).

  • A stream of traffic going straight ahead on approach #1, with a gap in it too short to make the signal end the green.

  • At least one car stopped at the stop line in the left turn lane on approach #1, waiting to turn left through a gap in opposing traffic on approach 2.

  • A cessation of straight ahead traffic on approach #2.

  • One car approaching on approach #2, wanting to turn left across the stream going straight on approach #1.

If the signal changes to serve the car turning left on approach #1, yellow trap is about to happen. But the drivers do not know what is happening:

  • The driver going straight on approach #1 can’t see the signals for approach #2 - he can’t see anything different until the arrow comes on 5-6 seconds after the trap is sprung.

  • The driver on approach #2 doesn’t know if both sides turned yellow, or if a yellow trap happened and only his light turned yellow. If he never heard of yellow trap, he will probably turn, expecting the stream to stop for the light.

Even if your state has the best driver training in the world, and teaches the left-turning driver to look for the signs of an impending yellow trap, there is always the driver from another state that doesn’t train for it. And he might be from a jurisdiction that has no left turn signals.

Flashing yellow arrows removes this scenario. If the left turner on approach #2 gets a solid yellow arrow to end the flashing yellow arrow, the opposing straight ahead driver gets a circular yellow at the same time. The flashing yellow arrow flashes any time the opposing signal is circular green. They must always end at the same time, because they are wired together.

This can’t be done if the circular green is the indication for a permissive turn.

You won’t be able to stop this. It is already law in several states, because it eliminates the hazard without eliminating the permissive turn.

This is NOT a matter of driver training, because it takes very careful inspection to detect the yellow trap before it is too late.

Sorry, but whether or not there is a yellow trap, all drivers should know to yield to oncoming traffic with anything except a green arrow. At any time, on any day, I can show you people who don’t know to yield to oncoming traffic, especially when oncoming drivers are planing to turn right. In practice this is a problem even without the “yellow trap.” The “yellow trap” simply makes this lack of training more evident than it would be otherwise.

Did you start this thread to impose your will on everyone else or did you do it to discuss opposing view points?

I like your explanation, but here’s my problem with the new system: it overloads the meaning of a yellow arrow.

Today, anytime I see a yellow arrow, that means I can turn left exclusively…I have a protected left turn, and i do NOT need to worry about oncoming traffic (unless someone is running a red light).

Now, if i see a yellow left turn arrow, I don’t know if that’s a “turn left with caution, there might be oncoming traffic” or a “you have a protected left turn that’s about to end” signal.

Yes, one is flashing and the other isn’t, but if i’m trying to get through the intersection and glance up, see the yellow arrow, and glance down to continue my turn, i may not notice that that light was blinking, not solid.

We’ve added a second meaning to “yellow left turn” which completely contradicts the previous meaning… that is HUGE problem for safety in my mind. There are going to be cases of people seeing the yellow left turn light, assuming that means “protected left turn, about to end…better gun it through the intersection” and t-boning/being t-boned by the oncoming traffic that they assumed was stopped.

If you can address that concern for me, i’d be fine with this idea.

I started it to explain the flashing yellow arrow to the hosts, who complained about it in a now-closed thread.

Today, anytime I see a yellow arrow, that means I can turn left exclusively…I have a protected left turn, and i do NOT need to worry about oncoming traffic (unless someone is running a red light).

The yellow arrow NEVER had this meaning.

The steady yellow arrow had a meaning that you could turn, watching for conflict in the 1950s. It now means that a green arrow or flashing yellow arrow is ending.

The flashing yellow arrow used to have a redundant meaning the same as a flashing circular yellow - caution. But the government has already redefined the flashing yellow arrow to mean yield to conflict.

Now, if i see a yellow left turn arrow, I don’t know if that’s a “turn left with caution, there might be oncoming traffic” or a “you have a protected left turn that’s about to end” signal.

It depends on whether the yellow arrow is flashing or steady.

Yes, one is flashing and the other isn’t, but if i’m trying to get through the intersection and glance up, see the yellow arrow, and glance down to continue my turn, i may not notice that that light was blinking, not solid.

One is also higher in the signal face than the other.

We’ve added a second meaning to “yellow left turn” which completely contradicts the previous meaning… that is HUGE problem for safety in my mind. There are going to be cases of people seeing the yellow left turn light, assuming that means “protected left turn, about to end…better gun it through the intersection” and t-boning/being t-boned by the oncoming traffic that they assumed was stopped.

It means “left turn movement about to end, better stop.”

If you can address that concern for me, i’d be fine with this idea.

Usually the driver has seen the signal for some time before becoming too close to the intersection to be safe.

I actually did address it in a memo to the US DOT. They said that in practice, it was not a problem. The arrows are in different signal sections, arranged as listed:

Red arrow
Yellow clearance arrow
Flashing yellow arrow
Green arrow

The real trouble with this occurs at night, if the signal housing is painted a dark color. Then, the driver can’t tell which section the arrow is in. But again, observation over time tells the driver which arrow it is.

A suggestion is to place a retroreflective yellow border around the signal face. This is also being added as an option.

Note that, if the driver is not totally unobservant, what the signal previously indicated can also determine whether the light is flashing or steady.

  • A steady yellow arrow can’t follow anything except a green arrow, a flashing yellow arrow, or a flashing red arrow. It must follow them when the right-of-way is being reduced.

  • A steady yellow arrow must be followed by a flashing yellow arrow, a flashing red arrow, or a steady red arrow.

  • A flashing yellow arrow can’t directly follow anything except a steady yellow arrow or a red arrow.

  • A flashing yellow arrow must be followed by a steady yellow arrow or a green arrow.

  • A steady yellow arrow can’t be lit more than 6 seconds.

The yellow arrow NEVER had this meaning.

The steady yellow arrow had a meaning that you could turn, watching for conflict in the 1950s. It now means that a green arrow or flashing yellow arrow is ending.

certainly it has this meaning (can turn left exclusively) today. “green arrow ending” means the same thing as “can turn left exclusively (but not for much longer)”

You seem to acknowledge this point later in your post, discussing all the ways in which drivers can differentiate the two, and the rules about use to avoid confusion, so i’m not sure why you initially claim it doesn’t have this meaning (I wasn’t aware of what it meant in the 50s, i’m afraid I wasn’t around then, so that’s interesting that it has already changed meanings).

Further, even a flashing circular yellow today means “proceed with caution but you have right of way”. So the flashing left arrow does not really mimic a flashing circular yellow, because while you are proceeding with caution, you do NOT have right of way.

That said, I’m glad to hear that this issue has been considered and safeguards put in place to help avoid the confusion of meaning. I’m not sure i’m convinced it’s enough, or a good idea, but at least there is an acknowledgement of the issue.

Ending of the left turn exclusively is the meaning it has in Ohio. It is taught that way in drivers ed. I was raised by a 30 year Akron cop, I think I know what the lights mean, but I called out to the Ohio BMV to make sure and they confirmed it.

Check page 58 (63 if you count the covers)of the Ohio BMV handbook: http://www.bmv.ohio.gov/pdf_forms/HSY-7607.pdf
The yellow arrow is to clear a vehicle out of the intersection that is attempting to make a left turn.

Actually, the flashing yellow arrow was disused for most of the time. A few jurisdictions used it to indicate a continuous movement that had a conflict.

Flashing yellow arrow always had the meaning that left turns must yield to opposing traffic, but its use was restricted to times when the entire intersection was flashing (in low traffic periods). It was allowed to be used only where the signal face had no circular yellow to be flashed instead.

In the 1950s, Indianapolis IN had a nonconforming use of the yellow arrow. At the time, the Manual of Uniform Traffic Control Devices (MUTCD) defined green arrows, but not yellow or red arrows. Indianapolis used a steady yellow arrow to indicate a left turn that was protected from oncoming vehicles, but had a pedestrian conflict (due to the lack of pedestrian signals).

At the same time, St. Louis MO had a nonconforming use of the red arrow. It was used to require all vehicles seeing it to turn in the direction of the arrow.

In 1971, the MUTCD had a statement that a flashing arrow indication had the same meaning as the corresponding flashing circular indication. It prohibited flashing green indications.

The 2003 manual has the following list of meanings:

  • Steady circular red: Stop. After the stop, a permitted turn on red can be made if not prohibited by a sign (2 states do not allow the turn on red).

  • Flashing circular red: This is the same as a STOP sign. Stop, then go when the way is clear.

  • Steady red arrow: Absolute stop (for traffic intending to go in the direction of the arrow). No turns on red are permitted in the direction of the arrow. Note that a straight-ahead red arrow is not allowed.

  • Flashing red arrow: Stop (for traffic intending to go in the direction of the arrow). You may turn on red in the direction of the arrow when the way is clear. Note that a straight-ahead red arrow is not allowed.

  • Steady circular yellow: The right of way is ending. Stop if it is safe to do so.

  • Flashing circular yellow: Proceed, but watch for conflict. Left turning traffic must yield to opposing vehicles. All turning traffic must yield to pedestrians.

  • Steady yellow arrow: The right of way is ending. (for traffic intending to go in the direction of the arrow). Stop if it is safe to do so. Note that a straight-ahead yellow arrow is not allowed.

  • Flashing yellow arrow - 2000 and earlier MUTCD: Proceed, but watch for conflict. Left turning traffic must yield to opposing vehicles. All turning traffic must yield to pedestrians. This was used only when the traffic signals were in flashing mode - combinations of flashing and steady indications at the same intersection at the same time were prohibited. Note that a straight-ahead yellow arrow is not allowed.

  • Flashing yellow arrow - 2003 MUTCD: Not defined, due to ongoing research. Existing uses were required to be removed. Combinations of flashing and steady indications at the same intersection at the same time were prohibited. Note that a straight-ahead yellow arrow is not allowed. The flashing yellow arrow left turn signal was allowed by obtaining a research permit. In 2008, it was made generally available as a pending rule change.

  • Flashing yellow arrow - Forthcoming 2009 manual: Yield to conflicting traffic. Note that a straight-ahead yellow arrow is not allowed. The prohibition of mixing steady and flashing indications at the same intersection was removed.

  • Steady circular green: Proceed, but watch for conflict. Left turning traffic must yield to opposing vehicles. All turning traffic must yield to pedestrians.

  • Flashing circular green: This indication is strictly prohibited by the MUTCD.

  • Steady green arrow: Go (for traffic intending to go in the direction of the arrow). Conflicts are not allowed to be released by the signal. Turns on red are not allowed into the lane receiving the movement (not all jurisdictions are careful to obey this restriction on turn on red).

  • Flashing green arrow: This indication is strictly prohibited by the MUTCD.


The researchers trying to find a new indication for a permissive turn that could be displayed independently of the circular green considered and rejected several other options:

  • Louvered circular green: this is in use, but can’t be used with span wire or swinging mounts, because the wind might display it to straight-ahead traffic.

  • Circular green on the left turn signal, displayed at different times in the cycle (compared with the straight ahead circular green): Too confusing, especially at night. A wrong interpretation causes a crash. Requires a special sign.

  • Flashing green arrow: Would cause accidents with drivers from Canada, South Africa, New Zealand, and other countries where the steady green arrow requires all traffic to turn off in the direction of the arrow, and the flashing green arrow is a protected turn.

  • Flashing circular green: Would cause accidents with drivers from Canada and eastern Europe. Canada uses a flashing circular green as a protected left turn, and eastern Europe uses it as an indication the yellow is coming in 5 seconds.

  • Orange arrow: Orange is reserved for pedestrians. Confusing for the color blind. Other colors were rejected for the same reasons.

  • Yellow shapes were tried (particularly triangles), but the shape was often not discernible as a shape at night.

Many driving simulator and field studies were done before the flashing yellow arrow was chosen.


Actually, the only difference between a circular green and a flashing circular yellow is that cross street traffic going straight or turning left has a circular red, and is not allowed to move across traffic with a circular green. Such movements are usually shown a flashing circular red when a flashing yellow is displayed, and are allowed to move.

Do we need to go back to driving school? I see your point Troubleshooter, but people need to not drive into intersection to begin with, you’re sticking your hand into the lion’s pit. What if emergency vehicle and there’s a dunce in the intersection. I’ve basically had to relearn to drive with my profession, driving. It all boils down to impatient people. Calm down, slow down, listen to talk radio, chill, have a cigar, smile and wave randomly, and please respect our law enforcement officials. Move over when you see a traffic stop, do your part to ensure they go home to their families like you go home to yours.
Thanks for the replies that are not condescending, it’s great to hear everybody’s opinion.

Why do you think I am the one who is doing this?

The federal government is doing this. I am just explaining the inevitable change in the rules that is shortly to come. Be ready for it. It is being done because the yellow trap is causing too many avoidable accidents, and the lack of a separately terminated indication for permissive turns is responsible.

We are not going to have proper training as long as the people running the driving schools do not recognize the hazards. They are telling people to drive stupidly (I thought removing the government-run training from the schools was a mistake). They are telling people to wait in the intersection, or they won’t be allowed to make their left turns. They are also telling people to tailgate to make the driver ahead speed up. Both are extremely dangerous.

And it doesn’t help that the questions on the driver exam are ambiguous. Example:

“You are approaching a green traffic signal, and a policeman makes a signal for you to stop. You must obey the signal. TRUE FALSE”

Which signal???

We have had quite a few changes to the meanings of traffic control devices in the past:

  • Some states still prohibit the use of red arrows on signals. That will change shortly, because the 2009 federal standard will no longer allow the use of a circular red on an exclusively protected left turn signal. All states that do not comply will lose federal highway funds.

  • Beginning in 2003, left turn signals containing circular greens are not allowed to be placed to the left of the extension of the lane line separating the left turn lane from the adjacent straight ahead lane.

  • Beginning in 2009, the signal for an approach with a shared left turn and straight ahead lane is not allowed to begin or end the left turn and straight ahead phases at different times in the cycle.

  • Before 1971, yellow lines on the pavement or curb meant a prohibition of crossing or parking. Now yellow means that traffic in the other side of the line is going the other way, and a solid line means a prohibition of crossing the line except to turn left. Red paint means a prohibition of entering.

  • At one time, the state of Georgia placed the no-passing line at the right edge of the road.

  • At one time, there was no visible difference between a protected and a permissive turn at a signal. A green arrow merely permitted a turn in the indicated direction. It didn’t guarantee protection from other movements.

  • Stop signs used to be black lettering on a yellow octagon.

  • Many states didn’t have Yield signs until 1961.

  • Green arrows used to just disappear to indicate the protected movement ended. Sometimes there was no clearance period before the circular green was shown to opposing traffic. The yellow arrow was added for clearance in 1971, but not required until 1978.

  • Before 1971, whether a left turn was exclusively protected, or protected-permissive was indicated by a sign next to the signal: “LEFT TURN ON ARROW ONLY”, or “LEFT TURN GREEN OR ARROW”. Of course, government misused the English language and put the word “only” in the wrong place. I saw one of those signs the other day that had never been taken down.

  • At one time, every freeway entrance ramp had a YIELD sign on it. This caused numerous crashes. Now the merge sign appears on the main freeway instead, and the responsibility for a safe merge has been transferred to drivers in the lane the ramp is merging into.

  • At one time, traffic lights had only red and green, and both lights came on at the same time to indicate a change. This is now strictly prohibited.

  • Traffic signals used to turn the lights yellow in all directions to indicate a change. This is now strictly prohibited.

  • A green arrow used to be put in the signal face over a lane to indicate that the lane was required to turn, instead of using the (arrow) ONLY sign. They were often displayed in conflict with pedestrians crossing the street with a walk indication.

Akron police confirmed that the yellow arrow means that it is ending left turns right of way and clear the intersection, so does Ohio Highway Patrol. Are you saying that the Ohio BMV, their manual that they currently give out, Ohio’s driver ed, APD, and Ohio Highway Patrol are all wrong?

Link us to some of these rules and manuals you are quoting.