Wisconsin Department
of Transportation
Intelligent Transportation Systems (ITS)
Design Manual
CHAPTER 14
ELECTRONIC BLANK-OUT
SIGNS
December, 2000
Wisconsin Department
of Transportation
14.
Intelligent Transportation Systems (ITS)
Design Manual
Electronic Blank-Out Signs
14.1.
Introduction and Usage
In urbanized areas motorists require clear and highly legible messages for safe guidance along
freeways and arterial streets. Electronic Blank-Out Signs installed at strategic locations can
significantly enhance message importance when compared to traditional static signs due to
inherent operational characteristics. Electronic Blank-Out Signs incorporate a variety of
different message types and can be controlled through various methods. Fiber Optic and Light
Emitting Diode (LED) Electronic blank sign technology have emerged as industry standards.
Each sign technology has a variation of characteristics.
14.2.
Blank-Out Sign Types
Electronic Blank-Out Signs are used in Wisconsin and other areas of the world for various
traffic management and traveler information applications. Figure 14-1 and Figure 14-2 highlight
current applications of Electronic Blank-Out Signs in Wisconsin and a representative listing of
other uses on other areas of the world.
14.3.
Blank-Out Sign Design Considerations
Blank-Out Sign Message Content and Size
Most manufacturers are capable of manufacturing Blank-Out signs incorporating standard
FHWA legends available in single or multi-message overlay. Message content and character
sizing should follow practices associated with the MUTCD.
Sign Location
Installation of Electronic Blank-Out Signs are specific to each application and location. Location
of Electronic Blank Out Signs should be consistent with sound signing practices of the MUTCD.
Constraints that need to be considered during field investigation an plan developed are:
•
•
•
•
Location of Electronic Blank-Out Sign with respect to other signing, lighting and
utilities.
Assumed cone of vision of the proposed Blank-Out sign
Minimum vertical and lateral clearance requirements
Proximity to existing or proposed traffic management cabinets that will provide power
and communications to the sign.
Mechanical Construction
The mechanical construction portion of the report has been broken into three sections. A
housing section applies to both fiber optic and LED Electronic Blank-Out Signs. The second
and third sections highlights components internal and specific to fiber optic and LED Electronic
Blank-Out Signs, respectively.
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Wisconsin Department
of Transportation
Application
Ramp Metered
August, 2000
Intelligent Transportation Systems (ITS)
Design Manual
Description
Ramp Metered Blank Out Signs are incorporated
into the design of ramp meters when two highspeed roadway facilities intersect (e.g., freeway to
freeway, etc.). The Ramp Metered Electronic
Blank-Out Sign is typically integrated with the
installation of existing or new Type I Overhead
Freeway Signs. Also, Ramp Metered Blank-Out
Sign is installed in combination with two yellow
beacon wig-way lights (See Ramp Meter Design
Chapter for additional information).
Picture
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Wisconsin Department
of Transportation
Too Fast For
Curve
August, 2000
Intelligent Transportation Systems (ITS)
Design Manual
A single Too Fast for Curve Signs has been
installed at a location that has historical record of
truck rollovers. Specifically it is installed on the
approach to a freeway to freeway loop ramp. If a
vehicle approached the ramp too fast, the
Electronic Blank-Out Sign is activated. Also, the
Too Fast for Curve Blank-Out Sign is installed in
combination with two yellow beacon wig-way
lights
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Wisconsin Department
of Transportation
Intelligent Transportation Systems (ITS)
Design Manual
Weigh Station
Open / Closed
At weigh station locations throughout Wisconsin,
an Electronic Blank-Out Sign has been added to
an existing Type I Ground Mounted Freeway
Sign (3 per weigh station, typ.).
Do Not Cross to
<Hwy Name>
At entrance ramp locations where there is 1)high
mainline and ramp volume and 2) is in close
proximity to a major freeway system interchange
with left hand exits, Do Not Cross to <Highway
Name> Electronic Blank-Out Signs have been
installed. Specifically the signs have been
installed 100-200 ft. After the ramp meter stop bar
on multiple wood posts.
Merge Right
At dual lane loop ramps a Form Single Line
Electronic Blank-Out Signs have been installed to
minimize the potential of side swipe traffic
incidents during non metering periods. The signs
are typically installed near the ramp terminal and
are mounted on multiple wood poles.
Dynamic
Trailblazer
Signing
To assist in routing traffic through a corridor,
dynamic trailblazer signing provide a method to
change signing to freeway entrance ramps. (See
Dynamic Trailblazer Signing Design Chapter for
additional information – next submittal).
Figure 14-1: Electronic Blank-Out Sign Applications within Wisconsin.
Application
Reversible Lane Systems
Description
Allows agencies to manage intermittent
traffic congestion. Examples include
reversing lanes during peak inbound
and outbound periods and loading and
discharging of special events.
Picture
Toll Booth Traffic Control
and Guidance
Overheight Detection /
Warning and Tunnel
Traffic Control
Allows toll agencies to indicate which
collection booths are open and closed
Since an empty load or a slight increase
in tire pressure could push a truck’s
height just above an allowable clearance,
overhead detection / warning signing
can minimize the occurrence of
potentially catastrophic traffic incidents.
Parking Ramp Blank-Out Signing can
assist in guiding motorists to parking
ramp excess capacity. The signing can
assist in minimizing traffic congestion,
especially during special events.
HOV related Blank-Out Signing can
<picture forthcoming>
Parking Ramp Signage
HOV Systems
August, 2000
<picture forthcoming>
<picture forthcoming>
<picture forthcoming>
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Wisconsin Department
of Transportation
Variable Speed Limit Signs
Traffic Management Lane
Control Systems
Intelligent Transportation Systems (ITS)
Design Manual
inform motorists of lane use restrictions
and and availability.
Variable Speed Limit Signs can be used
for various applications such as work
and school zones.
When placed at ¼ to ½ mile intervals, a
series of lane control signs over each
travel lane can assist motorists in
determining appropriate lane
assignments during traffic incidents.
Lane Control Signs usually include a red
“X”, green and amber arrows.
<picture forthcoming>
Others
Figure 14-2: Representative International Electronic Blank-Out Signs Usage
Housings
Critical to the construction of any Electronic Blank-Out Sign is the housing that protects
internal components from the environment. Figure 14-3 provides guidelines when specifying
an enclosure for an Electronic Blank-Out Sign.
Fiber Optic Signs
Figure 14-4 provides guidelines when specifying internal components of a fiber optic Electronic
Blank-Out Sign.
LED Signs
Figure 14-5 provides guidelines when specifying internal components of an LED Electronic
Blank-Out Sign.
Sign Mounting
Electronic blank-out sign mounting is very dependant on sign manufacturer. However, all
mounting hardware must accommodate sign weight and wind loading of 80 mph. Other
Considerations for Sign mounting include:
•
•
Hardware Material – usually stainless steel hardware is required. In some cases,
hardware may need to be modified to accommodate aesthetic requirements (e.g.,
painting, ornaments, etc,)
Maintenance - Can the horizontal and vertical pitch of the sign be easily adjusted?
14.4.
Underground Infrastructure
When the Electronic Blank-Out Sign(s) and other supporting field elements (e.g.,
cabinets, power sources, etc.) have been placed, underground conduit infrastructure can be
designed. Issues to keep in mind when designing Electronic Blank-Out Sign conduit
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Intelligent Transportation Systems (ITS)
Design Manual
infrastructure include:
•
•
•
•
Pull Box Spacing - Pull boxes should be spaced within 200 feet.
Terrain - Conduit infrastructure should be designed on relatively flat (4:1 slope or
flatter) terrain. For steeper sloped terrain (3:1 or greater) , conduit may be run
perpendicular to (i.e., up or down) the slope to locations where the terrain is more
suitable for conduit installation.
Conduit Size - 3-Inch conduit is typically used for conduit raceways, since a) cost
savings between 3-inch and smaller diameter conduits is minimal, and b) 3-inch
conduit may provide for greater future expansion depending on the number of
cables and % fill of the conduit. 2-inch conduit must be used when entering
electrical service (meter) pedestals.
Conduit Fill - The size and number of conduits along a run is dependent on
percentage of fill as established by the National Electric Code (NEC). For new
conduit installation, the percent fill must not exceed 31%. For installation of cable in
existing conduit, 40% of the available area may be used.
14.5.
Sign Control
Each Electronic Blank-Out Sign requires power cabling and an activation device. Power
cable requirements are largely dependent on sign manufacturer, sign type, and power
consumption. Several existing Electronic Blank-Out Signs in Wisconsin have been integrated
into existing traffic management systems via model 170 traffic controllers or similar switchbased interfaces. Also, in some cases photocontrol devices can be integrated with a system of
Electronic Blank-Out Signs to automatically adjust brightness.
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Wisconsin Department
of Transportation
Intelligent Transportation Systems (ITS)
Design Manual
Blank-Out Sign Housing Checklist
Housing body and inside framework permanently attached to form a single unit
designed to withstand minimum 80 pounds per square foot as specified in
AASHTO publication entitled “Standard Specification for Structural Supports for
Highway Signs, Luminaires, and Traffic Signals”.
Housings constructed of extruded aluminum with a flat aluminum back welded
into the housing.
Housing NEMA 4 rated (protects from moisture, dust, dirt, and corrosion)
All corners and seams of the housing heli-arc welded to provide a weatherproof
seal around the entire case.
Continuous internally mounted stainless steel hinges connect the housing and
doors.
Extruded aluminum doors have one side removable to gain access to sign face
(not required for routine maintenance).
Neoprene door gaskets to provide weatherproof seal.
Flat aluminum sign face with fiber optics or LED assembly mounted to it.
Sign has one or more stainless steel, 1/4-turn link-locks per door to tightly secure
the door onto the gasket.
Mounting hubs of cast aluminum alloy with standard pipe thread.
(For Fiber Optic Enclosures) Front of the housing finished with an anti-glare
material
(For LED Enclosures) The housing includes a single sheet, UV stabilized, and UV
filtering polycarbonate front panel. The front panel employs a flat black antiglare sheeting substance, with appropriate cut outs for light emission.
Drainage provided by a minimum of one screened hole located at the housing
bottom.
The housing has a visor attached to protect the message from UV exposure.
If a clear Lexan thermodynamically-engineered forced-air housing ventilation
Figure 14-3: Blank-Out Sign Housing Checklist
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Wisconsin Department
of Transportation
Intelligent Transportation Systems (ITS)
Design Manual
Fiber Optic Blank-Out Sign Internal Component Checklist
All messages clearly legible, attracting attention under any lighting conditions.
At full intensity the sign will be highly visible anywhere within an approximate
60 degree cone centered about the optic axis.
The sign shall completely blank out when not energized. No phantom words or
legend seen under any ambient light conditions.
Messages are displayed by a single or double row of glass fiber bundles
(depending upon application).
In most applications bundles are arranged so that in the event of failure of one
light source, the other shall continue to provide a discernible message.
The color of any message may be changed in the field by replacement of the
color filters without removing the sign from the case.
Nominal 50 watt lamps are used and operated at appropriate DC voltage. The
lamps sustain an average 8,000-hour life.
Transformers are used to reduce the incoming 120 volts AC to appropriate DC
voltage. The transformers shall contain Class A insulation and weatherproofing
and shall be rated at 48.5 volt-amps.
The sign is capable of continuous operation over a range in temperature from -35
F to +165 F (-31 C to +75 C).
Fiber optic modules and associated components are assembled directly to the
sign face and have an inside back cover to provide protection to the module. The
fiber consists of step-indexed fiber optic glass bundles arranged to define the
required message. The fiber optic bundles are ground smooth and optically
polished at the input and output ends for maximum light transmission.
Glass bundles are mounted through the sign face from the inside. Number of
bundles varies according to message.
Door panels and bundle termination holders are colored flat black to minimize
legibility when deactivated and maximize legibility when activated. No color
appears when deactivated regardless of ambient light conditions.
Message color is provided by a tempered, optically correct glass color filter in
conformance with applicable ITE specifications.
Electrical connection of field wires are made via barrier-type terminal strip.
All fasteners and hardware shall be corrosion-resistant stainless steel. All
components are readily accessible for maintenance when the door is open.
With standard hardware and locks, no tools are needed for lamp replacement.
Figure 14-4: Fiber Optic Blank-Out Sign Internal Component Checklist
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Wisconsin Department
of Transportation
Intelligent Transportation Systems (ITS)
Design Manual
LED Blank-Out Sign Internal Component Checklist
All messages clearly legible, attracting attention under any lighting conditions.
At full intensity the sign will be highly visible anywhere within an approximate
60 degree cone centered about the optic axis.
The sign shall completely blank out when not energized. No phantom words or
legend seen under any ambient light conditions.
Messages are displayed by a single or double row of glass fiber bundles
(depending upon application).
In most applications bundles are arranged so that in the event of failure of one
light source, the other shall continue to provide a discernible message.
The color of any message may be changed in the field by replacement of the
color filters without removing the sign from the case.
Nominal 50 watt lamps are used and operated at appropriate DC voltage. The
lamps sustain an average 8,000-hour life.
Transformers are used to reduce the incoming 120 volts AC to appropriate DC
voltage. The transformers shall contain Class A insulation and weatherproofing
and shall be rated at 48.5 volt-amps.
The sign is capable of continuous operation over a range in temperature from -35
F to +165 F (-31 C to +75 C).
Fiber optic modules and associated components are assembled directly to the
sign face and have an inside back cover to provide protection to the module. The
fiber consists of step-indexed fiber optic glass bundles arranged to define the
required message. The fiber optic bundles are ground smooth and optically
polished at the input and output ends for maximum light transmission.
Glass bundles are mounted through the sign face from the inside. Number of
bundles varies according to message.
Door panels and bundle termination holders are colored flat black to minimize
legibility when deactivated and maximize legibility when activated. No color
appears when deactivated regardless of ambient light conditions.
Message color is provided by a tempered, optically correct glass color filter in
conformance with applicable ITE specifications.
Electrical connection of field wires are made via barrier-type terminal strip.
All fasteners and hardware shall be corrosion-resistant stainless steel. All
components are readily accessible for maintenance when the door is open.
With standard hardware and locks, no tools are needed for lamp replacement.
Figure 14-5: LED Blank-Out Sign Internal Component Checklist
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Wisconsin Department
of Transportation
14.6.
Intelligent Transportation Systems (ITS)
Design Manual
Blank-Out Sign Construction Details
Construction details previously used during construction of blank-out signs in District 2
are found in Figure 14-6. These details can be found in Appendix A. Electronic Microstation
versions of these files can be obtained by contacting the Freeway Operations Unit.
* Construction details are currently being refined, and will be updated in the next
submission.
File Name
trailblz
speedsign
dontcross
Description
DYNAMIC TRAILBLAZER ASSEMBLY
LED SPEED SIGNS
LED BLANK-OUT SIGN
Figure 14-6: Blank-out Sign Construction Details
14.7.
Blank-Out Sign Special Provisions
Special provisions for items used in contracts containing blank-out signs are listed in
Figure 14-7. These special provisions can be found in Appendix B. Electronic files of the
special provisions (Microsoft Word version 7.0) can be obtained by contacting the Freeway
Operations Unit. * Special provisions are currently being refined, and will be updated in the
next submission.
Filename
dontcrosssign
relayassembly
trailblazer
Description
FIBER OPTIC BLANK-OUT SIGN, ITEM 90005
RELAY ASSEMBLY, ITEM 90005
DYNAMIC TRAILBLAZER J3 ARROW ASSEMBLY, ITEM 90005; DYNAMIC
TRAILBLAZER J2 ARROW ASSEMBLY, ITEM 90005; DYNAMIC
TRAILBLAZER BY-PASS ASSEMBLY, ITEM 90005
Figure 14-7: Blank-out Sign Special Provisions
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