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902.12 Rectangular Rapid Flashing Beacons (MUTCD Chapter 4L): Difference between revisions

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==902.13.1 Application of Lane-Use Control Signals (MUTCD Section 4M.01)==
[[Category:902 Signals|902.13]]
'''Support.''' Lane-use control signals are special overhead signals that permit or prohibit the use of specific lanes of a street or highway or that indicate the impending prohibition of their use.  Lane-use control signals are distinguished by placement of special signal faces over a certain lane or lanes of the roadway and by their distinctive shapes and symbols.  Supplementary signs are sometimes used to explain their meaning and intent.
 
Lane-use control signals are most commonly used for reversible-lane control, but are also used in certain non-reversible lane applications and for toll plaza lanes (see MUTCD Section 4K.02).
 
'''Guidance.''' An engineering study should be conducted to determine whether a reversible-lane operation can be controlled satisfactorily by static signs (see MUTCD Section 2B.26) or whether lane-use control signals are necessary.  Lane-use control signals should be used to control reversible-lane operations if any of the following conditions are present:
 
:A. More than one lane is reversed in direction;
 
:B. Two-way or one-way left turns are allowed during peak-period reversible operations, but those turns are from a different lane than used during off-peak periods;
 
:C. Other unusual or complex operations are included in the reversible-lane pattern;
 
:D. Demonstrated crash experience occurring with reversible-lane operation controlled by static signs that can be corrected by using lane-use control signals at the times of transition between peak and off-peak patterns; and/or
 
:E. An engineering study indicates that the safety and efficiency of the traffic operations of a reversible-lane system would be improved by lane-use control signals.
 
'''Standard.''' Pavement markings (see MUTCD Section 3B.03) shall be used in conjunction with reversible-lane control signals.
 
'''Option.''' Lane-use control signals may also be used if there is no intent or need to reverse lanes, but there is a need to indicate the open or closed status of one or more lanes, such as:


:A. On a freeway, if it is desired to close certain lanes at certain hours to facilitate the merging of traffic from a ramp or other freeway;
=={{SpanID|902.12.1}}902.12.1  Application of Rectangular Rapid Flashing Beacons (MUTCD Section 4L.01)==


:B. On a freeway, near its terminus, to indicate a lane that ends;
'''Option. '''A pedestrian-activated and/or bicyclist-activated rectangular rapid flashing beacon (RRFB) may be used to provide supplemental emphasis to pedestrian, school, and trail warning signs at marked crosswalks across uncontrolled approaches.


:C. On a freeway or long bridge, to indicate that a lane may be temporarily blocked by a crash, breakdown, construction or maintenance activities, or similar temporary conditions; and
'''Standard. '''An RRFB shall only be installed to function as a Warning Beacon (see  [[--|EPG 902.18.3]]). Except as otherwise provided in this Chapter, all other provisions of the MUTCD applicable to Warning Beacons shall apply to RRFBs.


:D. On a conventional road or driveway, at access or egress points to or from a facility, such as a parking garage, where one or more lanes of the access or egress are opened or closed at various times.
An RRFB shall only be used to supplement a post-mounted W11-2 (Pedestrian), S1-1 (School), or W11-15 (Trail) crossing warning sign with a diagonal downward arrow (W16-7P) plaque, or an overhead-mounted W11-2 , S1-1, or W11-15 crossing warning sign, located at or immediately adjacent to a marked crosswalk.  


==902.13.2  Meaning of Lane-Use Control Signal Indications (MUTCD Section 4M.02)==
Except for crosswalks across the approach to or egress from a roundabout, or crosswalks across free-flow turn lanes separated by a channelizing island, an RRFB shall not be used for crosswalks across approaches controlled by YIELD signs, STOP signs, traffic control signals, or pedestrian hybrid beacons.


'''Standard.''' The meanings of lane-use control signal indications shall be as follows:
'''Option. '''An additional RRFB may be installed on that approach in advance of the crosswalk, as a Warning Beacon to supplement a W11-2 (Pedestrian), S1-1 (School),  or W11-15 (Trail) crossing warning sign with an AHEAD (W16-9P) or distance (W16-2P or W16-2aP) plaque.


:A. A steady DOWNWARD GREEN ARROW signal indication shall mean that a road user is permitted to drive in the lane over which the arrow signal indication is located.
'''Standard. '''If an additional RRFB is installed on the approach in advance of the crosswalk, it shall be supplemental to and not a replacement for the RRFB at the crosswalk itself.


:B. A steady YELLOW X signal indication shall mean that a road user is to prepare to vacate the lane over which the signal indication is located because a lane control change is being made to a steady RED X signal indication.
=={{SpanID|902.12.2}}902.12.2  Design of Rectangular Rapid Flashing Beacons (MUTCD Section 4L.02)==


:C. A steady RED X signal indication shall mean that a road user is not permitted to use the lane over which the signal indication is located and that this signal indication shall modify accordingly the meaning of other traffic controls present.
'''Standard. '''Each RRFB unit shall consist of two rapidly-flashed rectangular-shaped yellow indications, each with an LED-array based pulsing light source. The size of each RRFB indication shall be at least 5 inches wide by at least 2 inches high.


==902.13.3  Design of Lane-Use Control Signals (MUTCD Section 4M.03)==
The two RRFB indications for each RRFB unit shall be aligned horizontally, with the longer dimension horizontal and with a minimum space between the two indications of at least 7 inches, measured from nearest edge of one indication to the nearest edge of the other indication. The outside edges of the RRFB indications, including any housings, shall not project beyond the outside edges of the W11-2, S1-1, or W11-15 sign that it supplements.


'''Standard.''' All lane-use control signal indications shall be in units with rectangular signal faces and shall have opaque backgrounds. Nominal minimum height and width of each DOWNWARD GREEN ARROW, YELLOW X, and RED X signal face shall be 18 inches for typical applications.  Each lane to be reversed or closed shall have signal faces with a DOWNWARD GREEN ARROW and a RED X symbol.
An RRFB unit shall not be installed independent of the crossing warning signs for the approach that the RRFB faces. If the RRFB unit is supplementing a post-mounted sign, the RRFB unit shall be installed on the same support as the associated W11-2, S1-1, or W11-15 crossing warning sign and plaque. If the RRFB unit is supplementing an overhead-mounted sign, the RRFB unit shall be mounted directly above the top of sign or below the bottom of the sign.


Each non-reversible lane immediately adjacent to a reversible lane shall have signal indications that display a DOWNWARD GREEN ARROW to traffic traveling in the permitted direction and a RED X to traffic traveling in the opposite direction.
'''Option. '''As a specific exception to the eighth paragraph of  [[--|EPG 902.18.1]], the RRFB unit associated with a post-mounted sign and plaque may be located between and immediately adjacent to the bottom of the crossing warning sign and the top of the supplemental downward diagonal arrow plaque (or, in the case of a supplemental advance sign, the AHEAD or distance plaque) or within 12 inches above the crossing warning sign, rather than the recommended minimum of 12 inches above or below the sign assembly.


If in separate signal sections, the relative positions, from left to right, of the signal indications shall be RED X, YELLOW X, DOWNWARD GREEN ARROW.
'''Standard. '''For any approach on which RRFBs are used to supplement post-mounted signs, at least two W11-2 , S1-1, or W11-15 crossing warning signs (each with an RRFB unit and a W16-7P plaque) shall be installed at the crosswalk, one on the right-hand side of the roadway and one on the left-hand side of the roadway.


The color of lane-use control signal indications shall be clearly visible for 2,300 ft. at all times under normal atmospheric conditions, unless otherwise physically obstructed.
'''Guidance. '''On a divided highway, the left-hand side RRFB assembly should be installed in the median, if practicable, rather than on the far left side of the highway.


Lane-use control signal faces shall be located approximately over the center of the lane controlled.
When a pedestrian refuge island is installed in the middle of an undivided highway, an RRFB assembly should be installed on the raised median, if practicable, in addition to on the far left side of the highway, for a total of three RRFB assemblies facing each direction of traffic.


If the area to be controlled is more than 2,300 ft. long, or if the vertical or horizontal alignment is curved, intermediate lane-use control signal faces shall be located over each controlled lane at frequent intervals.  This location shall be so that road users will at all times be able to see at least one signal indication and preferably two along the roadway, and will have a definite indication of the lanes specifically reserved for their use.
Where the median island width is less than 10’, a single RRFB assembly should be installed in the middle of the island with signs and beacons facing both directions of traffic.


All lane-use control signal faces shall be located in a straight line across the roadway approximately at right angles to the roadway alignment.
Where the median island width is greater than 10’ an RRFB assembly should be installed on each side of the median island. Each RRFB assembly should have a sign and beacon facing traffic nearest to it.


On roadways having intersections controlled by traffic control signals, the lane-use control signal face shall be located sufficiently far in advance of or beyond such traffic control signals to prevent them from being misconstrued as traffic control signals.
'''Standard. '''For any approach on which RRFBs are used to supplement an overhead-mounted sign, at least one W11-2 , S1-1, or W11-15 crossing warning sign (without a W16-7P plaque) located approximately over the center of the lanes of the approach (or where optimum visibility can be achieved) shall be installed at the crosswalk.


Except as provided in the Option below, the bottom of the signal housing of any lane-use control signal face shall be a minimum of 16 ft. and a maximum of 19 ft. above the pavement grade.
If used at intersections, the design of the RRFBs shall conform to the requirements for post-mounted or overhead placement described in the third paragraph of this Article.  


'''Option.''' The bottom of a lane-use control signal housing may be lower than 16 ft. above the pavement if it is mounted on a canopy or other structure over the pavement, but not lower than the vertical clearance of the structure.
'''Option. '''RRFBs may be installed at intersections with more than one crosswalk on the same uncontrolled approach (see Figure 4L-1).  


Except for lane-use control signals at toll plazas (see MUTCD Section 4K.02), in areas with minimal visual clutter and with speeds of less than 40 mph, lane-use control signal faces with nominal height and width of 12 in. may be used for the DOWNWARD GREEN ARROW, YELLOW X, and RED X signal faces.
If used at intersections with two crosswalks on an uncontrolled approach, post-mounted RRFBs may be installed to face only one direction of travel at the first crosswalk that traffic encounters (see Figure 4L-1).  


Other sizes of lane-use control signal faces larger than 18 inches with message recognition distances appropriate to signal spacing may be used for the DOWNWARD GREEN ARROW, YELLOW X and RED X signal faces.
'''Standard. '''The light intensity of the yellow indications during daytime conditions shall meet the minimum specifications for Class 1 yellow peak luminous intensity in the publication “Directional Flashing Optical Warning Devices for Authorized Emergency, Maintenance, and Service Vehicles J595,” 2005, Society of Automotive Engineers (SAE).


Non-reversible lanes not immediately adjacent to a reversible lane on any street so controlled may also be provided with signal indications that display a DOWNWARD GREEN ARROW to traffic traveling in the permitted direction and a RED X to traffic traveling in the opposite direction.
'''Option. '''If the RRFB indications are so bright that they cause excessive glare during nighttime conditions, an automatic signal dimming device may be used to reduce the brilliance of the RRFB indications during nighttime conditions.


The signal indications provided for each lane may be in separate signal sections or may be superimposed in the same signal section.
'''Standard. '''If pedestrian push button detectors (rather than passive detection) are used to actuate the RRFB indications, a PUSH BUTTON FOR WARNING LIGHTS/WAIT FOR GAP IN TRAFFIC (R10-25) sign (see  [[--|Section 2B.58]]) shall be installed adjacent to a pedestrian push button detector explaining the purpose and use of the pedestrian push button detector.


==902.13.4  Operation of Lane-Use Control Signals (MUTCD Section 4M.04)==
'''Support.  [[--|EPG 902.9.5]] contains further information about pedestrian push button detector location criteria.


'''Standard.''' All lane-use control signals shall be coordinated so that all the signal indications along the controlled section of roadway are operated uniformly and consistently.  The lane-use control signal system shall be designed to reliably guard against showing any prohibited combination of signal indications to any traffic at any point in the controlled lanes.
Section 4H.12 contains information about bicyclist push buttons.  


For reversible-lane control signals, the following combination of signal indications shall not be simultaneously displayed over the same lane to both directions of travel:
'''Guidance. '''An audible information device should be used with RRFBs to assist pedestrians with vision disabilities.


:A. DOWNWARD GREEN ARROW in both directions,
'''Option. '''A small light directed at and visible to pedestrians in the crosswalk may be installed integral to the RRFB or pedestrian push button detector to give confirmation that the RRFB is in operation.


:B. YELLOW X in both directions,
=={{SpanID|902.12.3}}902.12.3  Operation of Rectangular Rapid Flashing Beacons (MUTCD Section 4L.03)==


:C. DOWNWARD GREEN ARROW in one direction and YELLOW X in the other direction.
'''Standard. '''The RRFB shall be normally dark, shall initiate operation only upon pedestrian actuation, and shall cease operation at a predetermined time after the pedestrian actuation or, with passive detection, after the pedestrian clears the crosswalk.


A moving condition in one direction shall be terminated either by the immediate display of a RED X signal indication or by a YELLOW X signal indication followed by a RED X signal indication.  In either case, the duration of the RED X signal indication shall be sufficient to allow clearance of the lane before any moving condition is allowed in the opposing direction.
All RRFB units associated with a given crosswalk (including those with an advance crossing sign, if used) shall, when activated, simultaneously commence operation of their rapid flashing indications and shall cease operation simultaneously.
If an automatic control system is used, a manual control to override the automatic control shall be provided.


'''Guidance.''' The type of control provided for reversible-lane operation should be such as to permit either automatic or manual operation of the lane-use control signals.
'''Guidance. '''The minimum duration of a predetermined period of operation of the RRFBs following each actuation should be based on the procedures for the timing of pedestrian clearance times for pedestrian signals (see  [[--|EPG 902.9.6]]).


'''Standard.''' If used, lane-use control signals shall be operated continuously, except that lane-use control signals that are used only for special events or other infrequent occurrences and lane-use control signals on non-reversible freeway lanes shall be permitted to be darkened when not in operation.  The change from normal operation to non-operation shall occur only when the lane-use control signals display signal indications that are appropriate for the lane use that applies when the signals are not operated.  The lane-use control signals shall display signal indications that are appropriate for the existing lane use when changed from non-operation to normal operations.  Also, traffic control devices shall clearly indicate the proper lane use when the lane control signals are not in operation.
'''Support. '''One consideration for lengthening the duration of the predetermined period of operation of the RRFBs is adding the perception/reaction time for pedestrians to confirm that a vehicle will yield or stop.  


'''Support.''' MUTCD Section 2B.26 contains additional information concerning considerations involving left-turn prohibitions in conjunction with reversible-lane operations.
'''Standard. '''The predetermined flash period shall be immediately initiated each and every time that a pedestrian is detected either through passive detection or as a result of a pedestrian pressing a push button detector, including when pedestrians are detected while the RRFBs are already flashing and when pedestrians are detected immediately after the RRFBs have ceased flashing.


When activated, the two yellow indications in each RRFB unit shall flash in a rapidly flashing sequence. As a specific exception to the requirements for the flash rate of beacons provided in the fifth paragraph of  [[--|EPG 902.18.1]], RRFBs shall use a much faster flash rate and shall provide 75 flashing sequences per minute.


Except as provided in the eighth paragraph of this Article, during each 800-millisecond flashing sequence, the left and right RRFB indications shall operate using the following sequence:
:A. The RRFB indication on the left-hand side shall be illuminated for approximately 50 milliseconds.
:B. Both RRFB indications shall be dark for approximately 50 milliseconds.
:C. The RRFB indication on the right-hand side shall be illuminated for approximately 50 milliseconds.
:D. Both RRFB indications shall be dark for approximately 50 milliseconds.
:E. The RRFB indication on the left-hand side shall be illuminated for approximately 50 milliseconds.
:F. Both RRFB indications shall be dark for approximately 50 milliseconds.
:G. The RRFB indication on the right-hand side shall be illuminated for approximately 50 milliseconds.
:H. Both RRFB indications shall be dark for approximately 50 milliseconds.
:I. Both RRFB indications shall be illuminated for approximately 50 milliseconds.
:J. Both RRFB indications shall be dark for approximately 50 milliseconds.
:K. Both RRFB indications shall be illuminated for approximately 50 milliseconds.
:L. Both RRFB indications shall be dark for approximately 250 milliseconds.


The flash rate of each individual RRFB indication, as applied over the full flashing sequence, shall not be more than 5 flashes per second, to avoid frequencies that might cause seizures.


 
If an audible information device is used in conjunction with an RRFB, the audible information device shall not use vibrotactile indications or percussive indications. The audible information device shall include a speech message that says, “Warning lights are flashing.” The audible message shall be spoken twice.
[[Category:902 Signals|902.13]]

Revision as of 04:18, 11 August 2025


902.12.1 Application of Rectangular Rapid Flashing Beacons (MUTCD Section 4L.01)

Option. A pedestrian-activated and/or bicyclist-activated rectangular rapid flashing beacon (RRFB) may be used to provide supplemental emphasis to pedestrian, school, and trail warning signs at marked crosswalks across uncontrolled approaches.

Standard. An RRFB shall only be installed to function as a Warning Beacon (see EPG 902.18.3). Except as otherwise provided in this Chapter, all other provisions of the MUTCD applicable to Warning Beacons shall apply to RRFBs.

An RRFB shall only be used to supplement a post-mounted W11-2 (Pedestrian), S1-1 (School), or W11-15 (Trail) crossing warning sign with a diagonal downward arrow (W16-7P) plaque, or an overhead-mounted W11-2 , S1-1, or W11-15 crossing warning sign, located at or immediately adjacent to a marked crosswalk.

Except for crosswalks across the approach to or egress from a roundabout, or crosswalks across free-flow turn lanes separated by a channelizing island, an RRFB shall not be used for crosswalks across approaches controlled by YIELD signs, STOP signs, traffic control signals, or pedestrian hybrid beacons.

Option. An additional RRFB may be installed on that approach in advance of the crosswalk, as a Warning Beacon to supplement a W11-2 (Pedestrian), S1-1 (School), or W11-15 (Trail) crossing warning sign with an AHEAD (W16-9P) or distance (W16-2P or W16-2aP) plaque.

Standard. If an additional RRFB is installed on the approach in advance of the crosswalk, it shall be supplemental to and not a replacement for the RRFB at the crosswalk itself.

902.12.2 Design of Rectangular Rapid Flashing Beacons (MUTCD Section 4L.02)

Standard. Each RRFB unit shall consist of two rapidly-flashed rectangular-shaped yellow indications, each with an LED-array based pulsing light source. The size of each RRFB indication shall be at least 5 inches wide by at least 2 inches high.

The two RRFB indications for each RRFB unit shall be aligned horizontally, with the longer dimension horizontal and with a minimum space between the two indications of at least 7 inches, measured from nearest edge of one indication to the nearest edge of the other indication. The outside edges of the RRFB indications, including any housings, shall not project beyond the outside edges of the W11-2, S1-1, or W11-15 sign that it supplements.

An RRFB unit shall not be installed independent of the crossing warning signs for the approach that the RRFB faces. If the RRFB unit is supplementing a post-mounted sign, the RRFB unit shall be installed on the same support as the associated W11-2, S1-1, or W11-15 crossing warning sign and plaque. If the RRFB unit is supplementing an overhead-mounted sign, the RRFB unit shall be mounted directly above the top of sign or below the bottom of the sign.

Option. As a specific exception to the eighth paragraph of EPG 902.18.1, the RRFB unit associated with a post-mounted sign and plaque may be located between and immediately adjacent to the bottom of the crossing warning sign and the top of the supplemental downward diagonal arrow plaque (or, in the case of a supplemental advance sign, the AHEAD or distance plaque) or within 12 inches above the crossing warning sign, rather than the recommended minimum of 12 inches above or below the sign assembly.

Standard. For any approach on which RRFBs are used to supplement post-mounted signs, at least two W11-2 , S1-1, or W11-15 crossing warning signs (each with an RRFB unit and a W16-7P plaque) shall be installed at the crosswalk, one on the right-hand side of the roadway and one on the left-hand side of the roadway.

Guidance. On a divided highway, the left-hand side RRFB assembly should be installed in the median, if practicable, rather than on the far left side of the highway.

When a pedestrian refuge island is installed in the middle of an undivided highway, an RRFB assembly should be installed on the raised median, if practicable, in addition to on the far left side of the highway, for a total of three RRFB assemblies facing each direction of traffic.

Where the median island width is less than 10’, a single RRFB assembly should be installed in the middle of the island with signs and beacons facing both directions of traffic.

Where the median island width is greater than 10’ an RRFB assembly should be installed on each side of the median island. Each RRFB assembly should have a sign and beacon facing traffic nearest to it.

Standard. For any approach on which RRFBs are used to supplement an overhead-mounted sign, at least one W11-2 , S1-1, or W11-15 crossing warning sign (without a W16-7P plaque) located approximately over the center of the lanes of the approach (or where optimum visibility can be achieved) shall be installed at the crosswalk.

If used at intersections, the design of the RRFBs shall conform to the requirements for post-mounted or overhead placement described in the third paragraph of this Article.

Option. RRFBs may be installed at intersections with more than one crosswalk on the same uncontrolled approach (see Figure 4L-1).

If used at intersections with two crosswalks on an uncontrolled approach, post-mounted RRFBs may be installed to face only one direction of travel at the first crosswalk that traffic encounters (see Figure 4L-1).

Standard. The light intensity of the yellow indications during daytime conditions shall meet the minimum specifications for Class 1 yellow peak luminous intensity in the publication “Directional Flashing Optical Warning Devices for Authorized Emergency, Maintenance, and Service Vehicles J595,” 2005, Society of Automotive Engineers (SAE).

Option. If the RRFB indications are so bright that they cause excessive glare during nighttime conditions, an automatic signal dimming device may be used to reduce the brilliance of the RRFB indications during nighttime conditions.

Standard. If pedestrian push button detectors (rather than passive detection) are used to actuate the RRFB indications, a PUSH BUTTON FOR WARNING LIGHTS/WAIT FOR GAP IN TRAFFIC (R10-25) sign (see Section 2B.58) shall be installed adjacent to a pedestrian push button detector explaining the purpose and use of the pedestrian push button detector.

Support. EPG 902.9.5 contains further information about pedestrian push button detector location criteria.

Section 4H.12 contains information about bicyclist push buttons.

Guidance. An audible information device should be used with RRFBs to assist pedestrians with vision disabilities.

Option. A small light directed at and visible to pedestrians in the crosswalk may be installed integral to the RRFB or pedestrian push button detector to give confirmation that the RRFB is in operation.

902.12.3 Operation of Rectangular Rapid Flashing Beacons (MUTCD Section 4L.03)

Standard. The RRFB shall be normally dark, shall initiate operation only upon pedestrian actuation, and shall cease operation at a predetermined time after the pedestrian actuation or, with passive detection, after the pedestrian clears the crosswalk.

All RRFB units associated with a given crosswalk (including those with an advance crossing sign, if used) shall, when activated, simultaneously commence operation of their rapid flashing indications and shall cease operation simultaneously.

Guidance. The minimum duration of a predetermined period of operation of the RRFBs following each actuation should be based on the procedures for the timing of pedestrian clearance times for pedestrian signals (see EPG 902.9.6).

Support. One consideration for lengthening the duration of the predetermined period of operation of the RRFBs is adding the perception/reaction time for pedestrians to confirm that a vehicle will yield or stop.

Standard. The predetermined flash period shall be immediately initiated each and every time that a pedestrian is detected either through passive detection or as a result of a pedestrian pressing a push button detector, including when pedestrians are detected while the RRFBs are already flashing and when pedestrians are detected immediately after the RRFBs have ceased flashing.

When activated, the two yellow indications in each RRFB unit shall flash in a rapidly flashing sequence. As a specific exception to the requirements for the flash rate of beacons provided in the fifth paragraph of EPG 902.18.1, RRFBs shall use a much faster flash rate and shall provide 75 flashing sequences per minute.

Except as provided in the eighth paragraph of this Article, during each 800-millisecond flashing sequence, the left and right RRFB indications shall operate using the following sequence:

A. The RRFB indication on the left-hand side shall be illuminated for approximately 50 milliseconds.
B. Both RRFB indications shall be dark for approximately 50 milliseconds.
C. The RRFB indication on the right-hand side shall be illuminated for approximately 50 milliseconds.
D. Both RRFB indications shall be dark for approximately 50 milliseconds.
E. The RRFB indication on the left-hand side shall be illuminated for approximately 50 milliseconds.
F. Both RRFB indications shall be dark for approximately 50 milliseconds.
G. The RRFB indication on the right-hand side shall be illuminated for approximately 50 milliseconds.
H. Both RRFB indications shall be dark for approximately 50 milliseconds.
I. Both RRFB indications shall be illuminated for approximately 50 milliseconds.
J. Both RRFB indications shall be dark for approximately 50 milliseconds.
K. Both RRFB indications shall be illuminated for approximately 50 milliseconds.
L. Both RRFB indications shall be dark for approximately 250 milliseconds.

The flash rate of each individual RRFB indication, as applied over the full flashing sequence, shall not be more than 5 flashes per second, to avoid frequencies that might cause seizures.

If an audible information device is used in conjunction with an RRFB, the audible information device shall not use vibrotactile indications or percussive indications. The audible information device shall include a speech message that says, “Warning lights are flashing.” The audible message shall be spoken twice.

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