Sign and Billboard Lighting
Billboards and signs are out there for only one reason; to catch peoples’ attention so they will read the message. And, it seems, what better way to get peoples’ attention than to bathe the message with excessively bright or flashing light or to have it displayed on a giant animated TV screen? But there’s a time and a place for everything. Having such visual blight in a residential zone or use can spoil residents’ quality of life. Similarly, having such a distraction on a limited-access highway near exit or entrance ramps or merging lanes should be questioned from a safety point of view. Having a sign or billboard lighted all night can be a waste of energy, an environmental blight, a visual eyesore, and a creator of unnecessary sky glow. It’s a big price to pay for the few drivers who might see the message after, say, midnight.
What’s the solution? Municipalities need to have ordinances in place that regulates what kinds of lighted signs and billboards are permitted where in the community, what kind of lighting will be permitted, how glare and light trespass will be controlled and at what time of day and how the lighting is to be extinguished.
Where – Assuming that lighted billboards and signs have their place in the community, the ordinance should specify where that place is or isn’t. As an example, their use could be limited to commercial and industrial zoning districts or highway zoning districts. Their use could be prohibited where the message face is visible from a residential use or within 400 feet of a residential use. Their use might be prohibited in environmentally sensitive areas near astronomical observatories. Their use within 1,000 feet of a limited access highway interchange or merging lane location could be prohibited.
What – Most conventional billboards and signs are lighted from the bottom of the sign and aimed up toward the sign. While this is typically done in the name of convenience of the folks who have to maintain the lighting, such an arrangement creates considerable sky glow caused by the light that does not hit the sign and thereby projected past the sign and by light that reflects off of the face of the sign and travels up into the air above. To avoid the consequences of that stray light, the ordinance consider the following language:
"Externally illuminated billboards and signs shall have luminaires mounted at the top of the billboard or sign and aimed downward. The luminaires shall be designed, fitted and aimed to shield the lamp and its reflective surfaces from off-site view and to place the light output onto and not beyond the sign or billboard. Lighting shall be by linear fluorescent unless it can be demonstrated to the satisfaction of the Municipality that equal or more superior results with respect to glare, light trespass and light pollution control can be achieved with another source"
To control the brightness of the sign, especially in or near residential and environmentally sensitive venues, consider requiring the following language:
"At no point on the face of the sign or billboard and at no time shall the illumination exceed 30-vertical footcandles during hours of darkness. For Internally illuminated signs, they shall have a dark field and light message and the aggregate output of the light sources shall not exceed 500 initial lamp lumens per square foot of sign face per side. Channel letter signs shall have dimming capability to allow adjustment of sign brightness when required by the Municipality to accommodate local ambient conditions. Rotating, traveling, pulsing, flashing or oscillating light sources, lasers, beacons, searchlights or strobe lighting shall not be permitted. The use of highly reflective signage that creates nuisance glare or a safety hazard shall not be permitted."
LED, solid-state or digital billboards and signs, as they are variously called, present a particular problem because they are typically animated and high brightness. Allowing conventional signs to be converted to digital should require a building permit application and or special-exception Zoning Hearing Board review. Consider the following additional requirements: Static message or image shall last no less than 8 seconds. Maximum transition time between successive static messages shall be 1 second and blending of static messages shall not be permitted. In the event of a malfunction, a default mechanism shall freeze the message in one position. At no point on the face of the billboard shall the luminance be in excess of 1,000 nits. Signs shall be dimmed automatically from 30 minutes after sunset to 30 minutes before sunrise to 5% of their daylight luminance setting. A sign shall be separated a minimum distance of one thousand two hundred (1,200) feet from any other outdoor advertising LED billboard.
When - Short of not allowing lighted billboards and signs, the next best way of controlling them is to require that lighted signs and billboards be extinguished at an appropriate hour. Consider the following language: "Off-premises billboards and signs shall be extinguished automatically by a programmable controller, with astronomical control and spring or battery power-outage reset, by no later than 11:00 each evening until dawn, except that signs for establishments (not companies) that operate or remain open past 11:00 p.m. may remain lighted no later than ½ hour past the time of the close of the establishment."
Submission Requirements - To assure that the municipality is getting what has been promised by the installer, the following language should be considered: "Applications for the lighting or relighting of signs and billboards shall be accompanied by a point-by-point plot of initial vertical illuminances on the sign or billboard face, catalog cuts of proposed lighting fixtures and any glare reduction devices and a description of lamps, mounting locations, aiming angles and proposed hours of operation and method for automatically extinguishing the lighting by the proposed hour."
For additional information:
Digital Billboard Recommendations and Comparisons to Conventional Billboards by Ian Lewin Ph.D., FIES, L.C.
(84 KB PDF file)
"Digital billboards operating at the luminance levels recommended in this report produce much
fewer lumens into the night sky than conventional bottom mounted lighting systems."
Information Sheet No. 35 from IDA on Billboard Lighting (PDF file)
