1. Define the Roadway Task First
Street lighting must support drivers, cyclists and pedestrians while respecting adjacent properties. Begin with road classification, conflict areas, pedestrian activity, pole positions and the authority’s maintained-lighting criteria.
Average illuminance alone is incomplete; uniformity, veiling luminance or luminance criteria, vertical visibility and disability glare may also govern. A retrofit that keeps old poles must account for their spacing and setbacks before a luminaire is selected.
For related planning resources, review the CPS Lighting product center.
2. Compare Photometry, Not Wattage
Wattage describes input power, not where the light lands. Request an IES photometric file and model the exact mounting height, arm length, tilt and road geometry.
Compare maintained results using an appropriate light-loss factor. A narrow optic may reach farther but becomes sensitive to pole position and aiming; a broad optic can improve near-pole coverage but increase backlight. Fixture lumens and efficacy are useful screening values, not substitutes for a roadway calculation.
| Metric | What it tells you | What it does not prove | Required check |
|---|---|---|---|
| Input watts | Electrical demand | Road coverage | Photometric model |
| Fixture lumens | Total initial output | Glare or uniformity | Candela distribution |
| BUG rating | Zonal backlight/uplight/glare limits | Compliance with every ordinance | Local code review |
| Surge rating | Defined test withstand level | Complete field reliability | Protection coordination |
| Rated life | Claim under stated conditions | Driver or system life by itself | Test basis and warranty |
For related planning resources, review the lighting case library.
3. Manage Glare, Spill and CCT
High-angle intensity can create glare even when the pavement receives enough light. Review the luminaire’s BUG rating, cutoff behavior and candela near critical viewing directions.
Limit uplight and backlight where ordinances or property boundaries require it. Warmer CCT can reduce short-wavelength content, but color choice must still support the visual task and local policy. The DarkSky/IES principles call for light that is useful, targeted, low level, controlled and warm-colored where possible.
For related planning resources, review the lighting news center.
4. Protect Drivers and Electronics
Outdoor drivers face heat, moisture and switching surges. Specify operating-temperature limits, surge protective devices, ingress protection, corrosion resistance and cable-entry details for the environment.
Surge ratings should be stated with test method and configuration, not as an isolated number. Thermal design matters because high internal temperature accelerates electronic aging. Ask whether the driver, SPD and photocontrol receptacle are field replaceable and whether opening the housing affects the seal or warranty.
For related planning resources, review the CPS Lighting company profile.
5. Controls and Network Decisions
Photocells, scheduled dimming and networked controls can reduce operating hours and provide fault data. They also add compatibility, cybersecurity, commissioning and long-term support questions.
Decide whether each point needs individual control or whether group control is enough. Define the dimming interface, fail-safe behavior, time synchronization, data ownership and replacement process. Verify low-level stability at night; a product that dims on a bench may still flicker when combined with field wiring and controls.
For related planning resources, review the project consultation team.
6. Evaluate Supplier and Lifecycle Cost
Compare bids through a compliance schedule covering photometry, construction, test evidence, warranty, spare parts, lead time and change control. Model lifecycle cost with local energy price, annual hours, dimming profile, cleaning, failure rate and access cost.
Avoid unsupported claims that every LED conversion saves the same percentage. The saving depends on the baseline system and control strategy. A strong supplier should provide samples, current test files, traceable model numbers and engineering support for the final calculation.
For related planning resources, review the CPS Lighting.
For tender comparisons, require every bidder to calculate the same road segment, maintenance factor and control schedule. Otherwise, superficially similar results may rely on incompatible assumptions.
7. Technical Sources
DarkSky/IES — Five Principles for Responsible Outdoor Lighting
U.S. DOE — Commercial and Industrial LED Luminaires
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