4.7 Bicycle Signal Faces & MUTCD Flashing Operation

4.7 Bicycle Signal Faces & MUTCD Flashing Operation

[!NOTE] Why this section exists: IMSA's Level III reference list requires familiarity with the current MUTCD in full, not just the warrant and display chapters. Two chapters are routinely skipped in signal training and routinely tested: Chapter 4H (Bicycle Signals), which the 11th Edition added as a full chapter, and Chapter 4G (Flashing Operation), which governs every flash event a technician will ever respond to.

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1. Bicycle Signal Faces (MUTCD Chapter 4H)

A bicycle signal face is a signal face whose indications are bicycle symbols rather than circular or arrow indications. It exists to give a bicyclist movement its own right-of-way assignment, separate from the adjacent motor vehicle movement.

When a Bicycle Signal Face May Be Used

Section 4H.01 makes the use of a bicycle signal face an Option, not a requirement. The decision should be made during the engineering study required by Section 4C.01, Paragraph 1, for a new signal, or by engineering judgment at an existing signal. Two Standards bound the Option:

• A bicycle signal face shall only be used to control bicyclist movements from a designated bicycle lane or path.
• It shall only be used where the bicyclist movements it controls are separated from the movements it does not control.

Guidance in Paragraph 10 adds the operational test: where motor vehicles can make the same movement, a bicycle signal face should be used only if the bicyclist movement is sometimes allowed to proceed or is sometimes required to stop when the parallel motor vehicle movement is not. If the bicycle always does exactly what the adjacent through movement does, the bicycle face adds cost and clutter without adding control.

Prohibited Uses (Section 4H.02, all Standards)

Prohibition 2 is the one field crews violate most often, usually by retrofitting a bicycle face onto a shared through/bike lane where a bicycle box was striped.

Signing, Layout, Size & Placement

• Bicycle Signal sign (Section 4H.03): an R10-41 series Bicycle Signal sign shall be installed immediately adjacent to — including above or below — every bicycle signal face. Minimum size is 24 in × 36 in next to an overhead face and 12 in × 21 in next to a post-mounted face. It may be omitted next to a supplemental near-side face.
• Layout (Section 4H.06): a bicycle signal face shall consist of all bicycle symbol signal indications. Circular or arrow indications shall not be mixed into a bicycle signal face.
• Size (Section 4H.07): three nominal sizes are recognized — 4, 8, and 12 inches — all indications in a face shall be the same size, and 4-inch indications shall not be used for any bicycle signal face other than a supplemental, post-mounted, near-side face. This is the only place in Part 4 where a 4-inch indication is legitimate.
• Placement (Section 4H.08): Sections 4D.05 through 4D.08 apply, with three exceptions:
  1. A minimum of one primary bicycle signal face is required, not two — an explicit exception to the two-face Standard of Section 4D.05.
  2. The primary bicycle face shall have 8-inch or 12-inch indications, even at the near side.
  3. When the primary face is more than 120 feet beyond the stop line, a supplemental near-side bicycle signal face shall be provided. Guidance adds that between 80 and 120 feet, a supplemental near-side face should be provided.
• Separation (Guidance): a bicycle face should be separated from the nearest vehicular face on the same approach by at least 3 feet, measured horizontally between face centers or vertically between the nearest indications.

Steady and Flashing Operation of Bicycle Faces

Section 4H.04 mirrors vehicular logic: a steady RED BICYCLE prohibits entry, a steady YELLOW BICYCLE shall follow a GREEN BICYCLE in the same face and shall be followed by a RED BICYCLE, and a steady GREEN BICYCLE is displayed only when the movement is permitted.

Section 4H.05 is the rule technicians most often get wrong: the mode of operation of the bicycle faces shall be the same as the mode of the other faces at that location. Bicycle faces operate steady when the intersection is steady and flash when the intersection flashes. A bicycle signal face shall not be placed in a dark mode while other vehicular faces are operating. Wiring a bicycle face so it goes dark on flash is a Standard violation, not an agency preference.

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2. Flashing Operation (MUTCD Chapter 4G)

Flashing mode is not a failure state — it is a defined operating mode with its own Standards, and it is the state a cabinet enters on every monitor trip, every manual flash switch throw, and every scheduled late-night flash program.

Flash Rate and Mechanism (Section 4G.01, Standards)

That last Standard is the design intent behind the flash transfer relay: flash must be a de-energized, fail-safe state that survives pulling the controller out of the cabinet. If a cabinet returns to steady operation when the controller is removed, it is non-compliant and unsafe.

Paragraph 7 is an Option: based on engineering study or judgment, a signal may be operated in flashing mode on a scheduled basis during one or more periods of the day.

Indications During Flash (Section 4G.03)

• Guidance: use flashing yellow on the major street and flashing red on the other approaches, unless flashing red is used on all approaches.
• Standard: all green indications shall be dark — not steady, not flashing — except a single-section continuously displayed GREEN ARROW used alone for a continuous movement, which shall remain continuously displayed during flash.
• Standard: flashing yellow may be used on more than one approach only if those approaches do not conflict with each other.
• Standard: one and only one indication in every signal face shall flash, except that a face with two identical CIRCULAR RED or RED ARROW indications may flash both.
• Standard: if a face contains both circular and arrow indications of the colour to be flashed, only the circular indication shall be flashed.
• Standard: all faces flashed on an approach shall flash the same colour, except that a separate turn face may flash RED ARROW while the adjacent through faces flash yellow. A shared turn face shall not flash CIRCULAR RED while the adjacent through movement flashes yellow.

Transitions Into and Out of Flash (Sections 4G.02 and 4G.04)

Entering flash from a monitor trip or a manual switch may happen at any time (Option). A programmed change into flash is constrained by Standard: it shall occur either at the end of the common major-street red interval, or directly from CIRCULAR GREEN to flashing CIRCULAR YELLOW, or from GREEN ARROW to flashing YELLOW ARROW, or from one flashing YELLOW ARROW section to another. And in every programmed change, no green or flashing yellow indication shall be terminated and immediately followed by a steady or flashing red without first displaying the steady yellow.

Leaving flash is equally constrained. From red-red flash, the flashing reds change to steady red, then to the green that begins the major-street green interval; Guidance sets the steady red clearance during that change at a minimum of 6 seconds. From yellow-red flash, the minor-street flashing reds go steady red immediately, and the major-street flashing yellows either go green in both directions or go steady yellow followed by a steady red clearance before green.

[!CAUTION] A cabinet that jumps from flashing yellow straight to red, or from flash straight to a green on the side street, is a Standard violation and a right-angle crash generator. When commissioning a scheduled flash program, always watch a full entry and exit sequence on site rather than trusting the controller's flash configuration screen.