A SECOND YELLOW TRAP HAZARD

WHAT CAUSES SECOND YELLOW TRAP?

Second yellow trap occurs only when there is a right turn green arrow on the right turn in conflict with the left turn that it traps. The conflict is a merging conflict, rather than a crossing conflict.

Second yellow trap occurs only under the following conditions:

  • The right turn signal is arranged to show a green arrow when the cross street left turn arrow is green.
  • The cross street left turn that overlaps this right turn is a leading left turn.
  • Any form of permissive left turn is used, including no left turn signals at all.
  • No clearance indication is displayed to the right turn.
  • The right turn is not channelized into its own exclusive lane
  • The law gives a right turn priority over an opposing left turn.

Second yellow trap does not occur if any of the following is true:

  • There is no right turn signal.
  • The right turn signal does not have an overlap phase with any cross street left turn.
  • The cross street left turn phase is not next (but watch for phase skip)
  • Exclusively protected* left turn phasing is used.
  • The right turn is channelized into its own exclusive lane.

The diagrams show the sequence of second yellow trap. Two second yellow traps on opposite corners are shown:

  1. The first diagram shows the most likely active phases before second yellow trap. The straight-ahead signals have circular green, and the left and right turns are permissive turns with either circular green or flashing yellow arrow.
  2. In the second diagram, the left-turn and straight-ahead signals receive yellow indications, but the right-turn signal is still either green or flashing yellow arrow. The left turns (red) are trapped by the right turns. These movement paths enter the same departure lanes, rather than crossing each other (as the primary yellow trap movements do).
  3. The third diagram shows the next phases, with the cross-street left turns overlapping the right turns with the green arrows.

The problem is in the MUTCD requirement that no clearance indication shall be displayed in the change from a permissive indication to a protected indication. This lack of a clearance indication means that traffic never stops flowing on that right turn. This can trap the left turning driver the same as regular yellow trap traps him.

permissive left turns

second yellow-trap occurs

cross lefts with overlaps

Notice in the following timing diagrams how this second yellow trap happens. The letters " YT " show where each second yellow trap happens:

Case 1: Exclusively Permissive*

The circular green left turn movement is yellow trapped by the right turn.
Time --->

2. Opposing circular
 2.
 2.
 2.
 2.
2. Opposing right turn
 2. Circular green
 2.
 3. Green arrow
 2. STOPPED
6. Left Turn circular
 6. Circular green
 6. YT 6. STOPPED
 6.
6. Adjacent circular
 6.
6.
 6.
 6.

--

Case 2: Exclusively Protected*

No yellow trap can occur.
Time --->

2. Opposing circular
 2.
 2.
 2.
 2.
2. Opposing right turn
 2. Circular green
 2.
 3. Green arrow
 2. STOPPED
1. Left turn arrow
 1. STOPPED
 1. STOPPED
 1. STOPPED
 1.
6. Adjacent circular
 6.
 6.
 6.
 6.

--

Case 3: Doghouse** Protected/Permissive

ANY circular green left turn movement is yellow trapped.
Time --->

2. Opposing circular
 2.
 2.
 2.
 2.
2. Opposing right turn
 2. Circular green
 2.
 3. Green arrow
 2. STOPPED
1. Left turn arrow
 6. STOPPED
 6. Circular greenYT 1. STOPPED
 6.
6. Adjacent circular
 6.

 6.
 6.
 6.

--

Case 4: Flashing Yellow Arrows Protected/Permissive

Flashing yellow arrow left turn movement is still yellow trapped.
Time --->

2. Opposing circular
 2.
 2.
 2.
 2.
2. Opposing right turn
 2. Flash yellow arrow
 2.
 3. Green arrow
 2. STOPPED
1. Left turn arrow
 2. Flash yellow arrow
 2.YT 1. STOPPED
 1.
6. Adjacent circular
 6.
 6.
 6.
 6.

--

Case 5: Flashing Yellow Arrows Protected/Permissive Lead-Lag

Flashing yellow arrow left turn movement is still yellow trapped.
Time --->

2. Opposing circular
 2.
 2.
 2.
 2.
2. Opposing right turn
 2. Flash yellow arrow
 2.
 3. Green arrow
 2. STOPPED
1. Left turn arrow
 2. Flash yellow arrow
 2.YT 1. STOPPED
 1.
6. Adjacent circular
 6.
 6.
 6.
 6.

CURING SECOND YELLOW TRAP

The following modifications will cure second yellow trap:

  • Remove the right turn signal. Use a shared face with only circular indications.
  • Change the right turn indication to a flashing red arrow during the circular green.
  • Channelize the right turn into its own lane.
  • Replace the right turn signal with an island and a YIELD sign.
  • Add a brief clearance and red indication (at least 5 seconds total) to the right turn.

The clearance and red indication added:

  1. The left-turn and right-turn movements have flashing yellow arrows while the straight-ahead movement has circular green.
  2. When the straight-ahead movements get circular yellow, the left turns and right turns get steady yellow arrows at the same time.
  3. The straight ahead and right turn yellows should change to red at the same time. The left-turn yellow arrow should be longer.
  4. All of these signals should be red together for at least 2 seconds.
  5. After the all-red period, the cross-street left turn can begin. The overlapping right turn should begin later.

The diagrams show how the modified sequence prevents second yellow trap:

  1. The first diagram again shows the most likely active phases before second yellow trap. The straight-ahead signals have circular green, and the left and right turns are permissive turns with either circular green or flashing yellow arrows.
  2. In the second diagram, the left-turn, straight-ahead, and right-turn signals all receive yellow indications. The left turns are not trapped by the right turns, because the right turns are stopped too. The left turns are allowed to stop or clear safely.
  3. The third diagram again shows the next phases, with the cross-street left turns overlapping the right turns with the green arrows.

The brief clearance and red indication  RC  are added to the right turn:

Permissive left turns

all red - yellow-trap prevented

cross lefts with overlaps

Case 1: Exclusively Permissive* - Fixed

The clearance and brief stop protects the circular green left-turn movement from second yellow trap.
Time --->

2. Opposing circular
 2.
 2.

 2.
 2.
2. Opposing right turn
 2. Circular green
 2.
RC 3. Green arrow
 2. STOPPED
6. Left Turn circular
 6. Circular green
 6.

6. STOPPED
 6.
6. Adjacent circular
 6.
6.

 6.
 6.

--

Case 7: Flashing Yellow Arrows Protected/Permissive Lead-Lag - Fixed

The extra clearance interval and brief stop prevents second yellow trap.
Time --->

2. Opposing circular
 2.
 2.

 2.
 2.
2. Opposing right turn
 2. Flash yellow arrow
 2.
RC 3. Green arrow
 2. STOPPED
1. Left turn arrow
 2. Flash yellow arrow
 2.

 1. STOPPED
 1.
6. Adjacent circular
 6.
 6.

 6.
 6.

* The phrases "permissive-only" and "protected-only" violate the grammar rules on the proper placement of the word "only" for the intended meaning. Government often misuses the word "only" by placing it in the wrong place. Correct usage places the word "only" (which is not an adverb) immediately before the word modified. My new usage substitutes the phrases, "exclusively permissive" and "exclusively protected."

** The term "doghouse" refers to the 5-section cluster shared left-turn signal face. But its good and bad properties also apply to the 5-section vertical and 5-section horizontal arrangements for shared left-turn faces. In this document, assume that any mention of the doghouse signal face also includes the other 5-section shared left-turn faces.

Links

  1. All Yellow Trap Links are here:
    YELLOW TRAP INDEX PAGE
  2. Preventing yellow trap in signal pre-emptions.
  3. Preventing Third Yellow Trap.
  4. Unusual Traffic Problems, Hazards, and Solutions
  5. Home