Illuminating signs, including electronic message centers (EMCs), at inappropriate lighting levels hurts everyone. If the LEDs that light the sign aren’t bright enough, then the sign won’t be legible at night, and the sign loses its nocturnal value. The energy used to light the sign is wasted.
Conversely, if the LEDs are lit too brightly, everyone also loses. The “sometimes more is less” axiom holds true, because when signs are lit too brightly, they become illegible. Plus the excessive brightness upsets people. Excessive energy use is coupled with ineffectiveness. Additionally, when LEDs are lit to intensities in excess of their intended use, their lifetime is exponentially shortened. And, once again, energy is wasted.
So, what is the “just right” illumination level?
The United States Sign Council commissioned The Thomas D. Larson Pennsylvania Transportation Institute at Pennsylvania State University to make this determination, specifically for LED illumination, in 2015. USSC has been working with Penn State (PSU) since 1996, and this collaboration subsequently produced 18 research projects directly related to optimum usage of on-premise signage.
PSU surveyed EMC manufacturing companies and asked their opinions about optimum lighting levels, but there was no consensus. Nor did prior research on the subject produce a consensus. So PSU set up two EMCs on its track at the Larson Institute and utilized 48 licensed drivers (an equal number of males and females). They read two words in 12-in.-tall letters from a distance of 360 ft. in eight sign-color combinations. http://www.ussc.org/wp-content/uploads/2017/07/USSC-National-On-Premise-Sign-Illumination-Guideline-Standards-7.10.17.pdf