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Old 05-23-2009, 10:33 AM
 
1,040 posts, read 782,071 times
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More on Flashing Yellow Arrows (FYA):

A. Over half of the states now contain at least one FYA installation. My current list includes:

AR AZ CA CO DC
DE FL GA IA ID
KY LA MD MI MN
MO MS MT NC NH
NJ NM NV OR TX
UT VA VT WA WI

B. The Federal Highway Administration has given interim approval of FYA, and is expected to make it a part of the 2009 Manual of Uniform Traffic Control Devices (MUTCD).

C. When properly implemented, FYA eliminates yellow trap.

D. The elimination of yellow trap allows traffic engineers to use lagging left turns more often (the green left turn arrow appears after the opposing straight ahead green).

E. FYA can NOT be used with lanes sharing left turn and straight ahead traffic. The doghouse display must be used for that. Shared lanes must not receive a green arrow without the circular green being on at the same time.

F. With the permissive/protected lagging left turn available, more streets can have progressed green lights (lights turn green as you come to them).

G. There will be fewer of those left turn collisions late at night where the two drivers don't agree on what color the light is (caused by yellow trap).

H. The period for permissive left turn is longer than when the circular green is used:

With the circular green "doghouse" signals:
1. Both directions have green left turn arrow.
2. Left turn A ends with yellow arrow.
3. Left turn B continues, with circular green B also on. Approach A has circular red.
4. Left turn B ends with yellow arrow.
5. Both directions have circular green, allowing permissive turns.
6. Both directions receive circular yellow, then red.

With FYA:
1. Both directions have green left turn arrow. Straight-ahead signals are circular red.
2. Left turn A ends with yellow arrow.
3. Left turn B continues, with circular green B also on. Left turn A has FYA, with circular red A also on.
4. Left turn B ends with yellow arrow.
5. Both directions have FYA, allowing permissive turns. Straight ahead signals are circular green.
6. Both directions receive yellow arrow and circular yellow, followed by red arrow and circular red.

I. FYA is the only display that can be legally programmed to change operating mode by time clock or computer control for different traffic conditions at different times of day:

- Exclusively permissive with light traffic, or when the cycle has no time for a minor movement (The green arrow never shows).
- Protected and permissive during medium traffic.
- Exclusively protected when traffic is such that a permissive turn is not safe (The flashing yellow arrow never shows).

Last edited by Troubleshooter; 05-23-2009 at 10:58 AM..
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Old 05-23-2009, 01:09 PM
 
Location: Charleston, SC
5,615 posts, read 14,232,046 times
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yep, they're all over the place in everett, wa! of course, none on any routes i travel regularly but there's always hope.

in san antonio i'd nominate bitters and huebner rd
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Old 05-25-2009, 12:11 PM
 
Location: San Antonio
1,314 posts, read 3,030,937 times
Reputation: 846
Quote:
Originally Posted by Troubleshooter View Post
More on Flashing Yellow Arrows (FYA):

C. When properly implemented, FYA eliminates yellow trap.

D. The elimination of yellow trap allows traffic engineers to use lagging left turns more often (the green left turn arrow appears after the opposing straight ahead green).
The doghouse display using Dallas phasing or one of its variants can also solve the yellow trap. But that nessecitates the use of louvres to screen the left-turn circular green from the through lanes, and the circular green being displayed for the left movement while the adjacent through movement has a red has proven quite confusing to motorists, especially when the left turn is not protected. The FYA solves that.

Quote:
E. FYA can NOT be used with lanes sharing left turn and straight ahead traffic. The doghouse display must be used for that. Shared lanes must not receive a green arrow without the circular green being on at the same time.
Here in SA, if there needs to be a protected turn in a shared-lane situation, it's usually done with a split-phase using a four-section stacked display.

Quote:
I. FYA is the only display that can be legally programmed to change operating mode by time clock or computer control for different traffic conditions at different times of day:
The City used to have a few intersections with a doghouse display where the protected left would only be available during certain times (i.e. the morning or evening rush hour or school hours). This was indicated by an adjacent sign reading "PROTECTED LEFT 4-6PM WEEKDAYS" or similar. The one at EB Braun at Old Tezel was switched to full-time operation about 6 months ago. The other one I'm aware of was on SB Nacogdoches at El Charro, which still appears to be there on Google StreetView. I'll have to take a drive over there one day soon.
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Old 05-25-2009, 10:02 PM
 
1,040 posts, read 782,071 times
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Quote:
Originally Posted by TexHwyMan View Post
The doghouse display using Dallas phasing or one of its variants can also solve the yellow trap. But that nessecitates the use of louvres to screen the left-turn circular green from the through lanes, and the circular green being displayed for the left movement while the adjacent through movement has a red has proven quite confusing to motorists, especially when the left turn is not protected. The FYA solves that.
I am quite familiar with it. That circular green can be confusing when the thru signals are red. There were also other attempts to create a signal that eliminates yellow trap, including:

- Inserting an all red period before the lagging left turn
- Using phase inhibit and call redirection to prevent an accidental lagging left turn due to phase skip
- Flashing circular red permissive after stop on left turn signal (MD, MI)
- Flashing red arrow for the same purpose (DE, CA)
- Flashing circular yellow permissive turn (WA)

Quote:
Here in SA, if there needs to be a protected turn in a shared-lane situation, it's usually done with a split-phase using a four-section stacked display.
We used to have some of those. Right now, we have one with the doghouse display and split phase on all 4 legs.

The new rule prohibits the flashing yellow arrow display where there is a shared use lane. The three section all arrow display, and the equivalent with a circular red, are prohibited except where the signal is operated split phase.

Quote:
The City used to have a few intersections with a doghouse display where the protected left would only be available during certain times (i.e. the morning or evening rush hour or school hours). This was indicated by an adjacent sign reading "PROTECTED LEFT 4-6PM WEEKDAYS" or similar. The one at EB Braun at Old Tezel was switched to full-time operation about 6 months ago. The other one I'm aware of was on SB Nacogdoches at El Charro, which still appears to be there on Google StreetView. I'll have to take a drive over there one day soon.
This is permitted. We have such a signal here that shuts off two left turn signals during rush hour.

What is not permitted with the doghouse display is the exclusively protected left turn (with no permissive turn). The circular display of a shared display must always show the same color the thru signals show.

Another new rule is that no display with a circular green in it can be placed to the left of an extension of the lane line between the left turn lane and the thru lane.
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Old 05-28-2009, 05:26 AM
 
27 posts, read 56,993 times
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Yeah, I was going to Mama Margies on 10 and Wurzbach. Saw this and freaked the heck out. I had been up in Lubbock for the past 9 months and didnt know what the heck it meant.

I realize now that I could have caused some accidents... seeing that it was 2:00am and all the bars in that area were letting out.
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Old 05-28-2009, 11:15 AM
 
1,040 posts, read 782,071 times
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Quote:
Originally Posted by cr1039 View Post
I still do not get why they don't just use a solid green light. That means unprotected left turn...

Anyway, I did see a few of these in Dallas last month, they had signs that indicated what the blinking yellow meant...I think it read:

"Unprotected left turn on blinking yellow arrow"

Genius...
They can't use the steady circular green, because the straight ahead (thru) traffic also sees and obeys that. They need a new indication, because they need to allow the permissive left turn at times when the thru signals are red. Without the flashing yellow arrow, there is no way to do this.

There are four cases:

- When the green arrow turns yellow, but the thru signals are still red (and may be red for a while), they can go ahead and allow the permissive turn through gaps in the opposing thru movement (which has just turned green). But they can't display a circular green then, because the opposing left turn still has a green arrow. But they can display a flashing yellow arrow then.

- If both directions on the street have circular greens, and the signal is told to cut off one of the circular greens to give an emergency vehicle special right-of-way, the left turn for the direction facing the resulting circular yellow MUST be shown an indication that will not cause drivers to quickly try to turn across opposing traffic that still has a circular green. Such a turn will cause an accident, because each driver believes the other will stop.

- If both directions on the street have circular greens, and the signal is pre-empted to cut off one of the circular greens to clear out a drawbridge or a railroad crossing, the left turn for the direction facing the resulting circular yellow MUST be shown an indication that will not cause drivers to quickly try to turn across opposing traffic that still has a circular green, for the same reason as above.

- If both directions on the street have circular greens, and the signal wants to cut off one of the circular greens to give the other direction a green left turn arrow, the left turn for the direction facing the resulting circular yellow MUST be allowed to continue turning left through gaps until the opposing circular green also turns yellow. If the left turn is given a yellow and red, the drivers will try to quickly turn across opposing traffic that still has a circular green. Because this causes an accident, this sequence must by law (2008) be prohibited, signed, or given a flashing yellow arrow.

The warning that the opposing traffic may have a green says "ONCOMING TRAFFIC MAY HAVE EXTENDED GREEN" on a yellow sign.

Last edited by Troubleshooter; 05-28-2009 at 11:31 AM.. Reason: clarity
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Old 07-18-2009, 10:17 PM
 
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I just got a peek at the latest trial revision of the next version of the Manual of Uniform Traffic Control Devices (MUTCD). There are some surprises:

- Separate left turn faces can no longer contain a circular green indication. This means the Dallas phasing system will no longer be allowed.

- Shared (thru and left) left turn faces can not be used in the exclusively protected mode unless the circular green and the green arrow begin and end at the same time. This requires separate phases for each approach (split phasing). It also prevents using exclusively protected as a left turn mode in a signal that changes left turn modes for different times of the day.

- A right turn can not have a green arrow if the opposing left turn is allowed by a circular green, flashing yellow arrow, or flashing red arrow. An exception is if the right turn is channelized into its own lane.

- Circular red is no longer allowed for a left turn signal face that is used in an exclusively protected mode. It must have a red arrow.

- Flashing yellow arrows can not be used with shared (thru and left) signal faces, or if one lane is shared between left turn and straight ahead.

- Turns on red are allowed if the right turn signal has a circular red, but not if it has a steady red arrow.

- Shared signal faces must be lined up with the lane line or divider between the left turn lane and the thru lane. Exclusive left turn faces must be lined up with the center fo the left turn lane.

- There will be a U-turn signal face.

- Strobes in signal lenses are prohibited, as are countdown vehicle indications.

- No clearance intervals shorter than 3 seconds.

With the same flashing yellow arrow face, the left turn mode can be switched among up to 6 different left turn modes, as is needed:

- Exclusively protected
- Protected/permissive with flashing yellow arrow
- Exclusively permissive with flashing yellow arrow
- Protected/permissive with flashing red arrow requiring stops
- Exclusively permissive with flashing red arrow requiring stops
- Prohibited turn (used to prevent a turn across an approaching train)

The following left turn phase patterns for one street can be implemented safely with flashing yellow arrows. These can also be varied by time of day:

- No left turn phase, but has fire, railroad, or drawbridge pre-emption
- Single lead (left turn before circular greens, opposing has flashing yellow arrow too, but no green arrow)
- Single lag (left turn after circular greens, opposing has flashing yellow arrow too, but no green arrow)
- Dual lead (both left turns before circular greens, turns end at same time)
- Dual split lead (both left turns before circular greens, turns end at different times)
- Dual unsplit lead-lag (split phasing - each approach has its own exclusive phase)
- Dual single-split lead (one left turn before circular greens, the other is after them)
- Dual double-split lead (one approach goes first, left and straight end at different times, other approach goes after them)
- Dual split lag (both left turns after circular greens, turns start at different times)
- Dual lag (both left turns after circular greens, turns end at same time)

Big changes are coming.

More states are now using Flashing Yellow Arrows. The total is now 35:

AK AL AG AZ CA
CO CT DC DE FL
GA IA ID KS KY
LA MD MI MN MO
MS MT NC NH NJ
NM NV OR TX UT
VA VT WA WI WY

Australia has them now too, as does South Africa.

Six states now require flashing yellow arrows for all new installations where they can be used:

AK MI MN OR TX WA

Last edited by Troubleshooter; 07-18-2009 at 11:08 PM..
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Old 11-19-2009, 02:56 PM
 
1,040 posts, read 782,071 times
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A couple of changes to this last post:

There is a typo in this paragraph:

Quote:
Originally Posted by Troubleshooter View Post
- Shared (thru and left) left turn faces can not be used in the exclusively protected mode unless the circular green and the green arrow begin and end at the same time. This requires separate phases for each approach (split phasing). It also prevents using exclusively protected as a left turn mode in a signal that changes left turn modes for different times of the day.
It should read

Quote:
- Shared (thru and left) left turn lanes can not be used in the exclusively protected mode unless the circular green and the green arrow begin and end at the same time. This requires separate phases for each approach (split phasing). It also prevents using exclusively protected as a left turn mode in a signal that changes left turn modes for different times of the day.
Even more states are now using Flashing Yellow Arrows. The total is now 38:

AK AL AR AZ CA
CO CT DC DE FL
GA IA ID KS KY
LA MD ME MI MN
MO MS MT NC NH
NJ NM NV NY OR
SC TX UT VA VT
WA WI WY

Guam also has them.

Australia has them now too, as does South Africa.

Six states now require flashing yellow arrows for all new installations where they can be used:

AK MI MN OR TX WA[/quote]
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Old 11-20-2009, 12:36 PM
 
Location: San Antonio
1,314 posts, read 3,030,937 times
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They're spreading throughout SA. The latest two I've spied are at Babcock/Prue and UTSA/Valero.
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Old 11-20-2009, 12:59 PM
 
Location: Charleston, SC
5,615 posts, read 14,232,046 times
Reputation: 2555
Still waiting for them at Bitters / Huebner. There's good visibility there... ideal location IMO.
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