Derby Downtown Lighting & Signage Plan

EXISTING CONDITIONS
2. LIGHTING QUALITY
The existing luminaires in the Derby District are anything but consistent in their quality
of illumination. The inconsistencies in lamp type, color quality and distribution lead to
significant inconsistencies in the light levels found throughout the district. These disparities
make Derby feel like an uncomfortable and unsafe place to be at night.
The majority of the existing luminaires appear to utilize high pressure sodium sources,
which are often very yellow in appearance and have poor color rendering characteristics.
The yellow color and low color rendering index (CRI) make it difficult to discern colors. The
poor color rendition can be problematic in public and retail areas where its important to
be able to identify people, their clothing and the color of vehicles. Additionally, due to the
poor performance of the existing lighting systems, the light levels are not uniform which
creates areas where it is difficult to maintain visual acuity. Vertical light levels are lacking
given the inconsistent spacing and locations of luminaires limiting the ability to see and
visually define spaces and people. All of these elements factor into people’s perception of
safety, or rather the lack there of, within the District at night.
Night time photo of existing luminaires with warm color temperature in the
Derby District.
Night time photo of existing luminaires with cool color temperature in the
Derby District
3. OPTICAL PERFORMANCE
The existing luminaires within the Derby District appear to have been installed at various times over
the past several decades. Given the advances in light sources and luminaire technology, most of the
optical components on the existing luminaires are outdated and do not comply with current design
standards. Examples would be the high pressure sodium cobra head type luminaires which utilize
outdated sag glass or dropped lens technology. These types of luminaires do not have good optical
control of the light distribution, resulting in high angels of glare, poor uniformity and trespass issues
with spill light falling in unintended locations. As such, these luminaires do not comply with today’s
full cut-off BUG type ratings or the International Dark-sky Association (IDA) efforts.
Examples of existing luminaires of various types in the Derby District that utilize dated sag glass or dropped lens technology which is not compliant with current
Dark-Sky standards.
Derby Lighting & Signage Plan
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