Chapter 4K. Flashing Beacons
Section 4K.01 General Design and Operation of Flashing Beacons
A Flashing Beacon is a highway traffic signal with one or more signal sections that operates in a flashing mode. It can provide traffic control when used as an intersection control beacon or warning in alternative uses.
Flashing Beacon units and their mountings shall follow the provisions of Chapter 4D, except as specified herein.
Beacons shall be flashed at a rate of not less than 50 nor more than 60 times per minute. The illuminated period of each flash shall not be less than one-half and not more than two-thirds of the total cycle.
If used to supplement a warning or regulatory sign, the edge of the beacon signal housing should normally be located no closer than 300 mm (12 in) outside of the nearest edge of the sign.
An automatic dimming device may be used to reduce the brilliance of flashing yellow signal indications during night operation.
Section 4K.02 Intersection Control Beacon
An Intersection Control Beacon shall consist of one or more signal faces directed toward each approach to an intersection. Each signal face shall consist of one or more signal sections of a standard traffic signal face, with flashing CIRCULAR YELLOW or CIRCULAR RED signal indications in each signal face. They shall be installed and used only at an intersection to control two or more directions of travel.
Application of Intersection Control Beacon signal indications shall be limited to the following:
- Yellow on one route (normally the major street) and red for the remaining approaches; and
- Red for all approaches (if the warrant for a multiway stop is satisfied). Flashing yellow signal indications shall not face conflicting vehicular approaches.
A STOP sign shall be used on approaches to which a flashing red signal indication is shown on an Intersection Control Beacon (see Section 2B.04).
An Intersection Control Beacon should not be mounted on a pedestal in the roadway unless the pedestal is within the confines of a traffic or pedestrian island.
Supplemental signal indications may be used on one or more approaches in order to provide adequate visibility to approaching road users.
Intersection Control Beacons may be used at intersections where traffic or physical conditions do not justify conventional traffic control signals but crash rates indicate the possibility of a special need.
An Intersection Control Beacon is generally located over the center of an intersection; however, it may be used at other suitable locations.
Section 4K.03 Warning Beacon
Typical applications of Warning Beacons include the following:
- At obstructions in or immediately adjacent to the roadway;
- As supplemental emphasis to warning signs;
- As emphasis for midblock crosswalks;
- On approaches to intersections where additional warning is required, or where special conditions exist; and
- As supplemental emphasis to regulatory signs, except STOP, YIELD, DO NOT ENTER, and SPEED LIMIT signs.
A Warning Beacon shall consist of one or more signal sections of a standard traffic signal face with a flashing CIRCULAR YELLOW signal indication in each signal section.
A Warning Beacon shall be used only to supplement an appropriate warning or regulatory sign or marker. The beacon shall not be included within the border of the sign except for SCHOOL SPEED LIMIT sign beacons.
Warning Beacons, if used at intersections, shall not face conflicting vehicular approaches.
If a Warning Beacon is suspended over the roadway, the clearance above the pavement shall be at least 4.6 m (15 ft) but not more than 5.8 m (19 ft).
The condition or regulation justifying Warning Beacons should largely govern their location with respect to the roadway.
If an obstruction is in or adjacent to the roadway, illumination of the lower portion or the beginning of the obstruction or a sign on or in front of the obstruction, in addition to the beacon, should be considered.
Warning Beacons should be operated only during those hours when the condition or regulation exists.
If Warning Beacons have more than one signal section, they may be flashed either alternately or simultaneously.
A flashing yellow beacon interconnected with a traffic signal controller assembly may be used with a traffic signal warning sign (see Section 2C.29).
Section 4K.04 Speed Limit Sign Beacon
A Speed Limit Sign Beacon shall be used only to supplement a Speed Limit sign.
A Speed Limit Sign Beacon shall consist of one or more signal sections of a standard traffic control signal face, with a flashing CIRCULAR YELLOW signal indication in each signal section. The signal lenses shall have a nominal diameter of not less than 200 mm (8 in). If two lenses are used, they shall be vertically aligned, except that they may be horizontally aligned if the Speed Limit (R2-1) sign is longer horizontally than vertically. If two lenses are used, they shall be alternately flashed.
A Speed Limit Sign Beacon may be used with a fixed or variable Speed Limit sign. If applicable, a flashing Speed Limit Sign Beacon (with an appropriate accompanying sign) may be used to indicate that the speed limit shown is in effect.
Section 7B.11 contains additional Options for the use of Speed Limit Sign Beacons with SCHOOL SPEED LIMIT signs.
Section 4K.05 Stop Beacon
A Stop Beacon shall consist of one or more signal sections of a standard traffic signal face with a flashing CIRCULAR RED signal indication in each signal section. If two horizontally aligned signal lenses are used, they shall be flashed simultaneously to avoid being confused with a highway-rail grade crossing flashing-light signals. If two vertically aligned signal lenses are used, they shall be flashed alternately.
The bottom of the signal housing of a Stop Beacon shall be not less than 300 mm (12 in) nor more than 600 mm (24 in) above the top of a STOP sign (see Section 2B.04).