A parking lot photometric plan shows the proposed fixture layout and calculated light levels across a site. It helps the project team review coverage, uniformity and property-line conditions against the selected requirements before poles and fixtures are installed.
This guide explains how to read and design a parking lot lighting plan, what uniformity ratios mean, and which requirements matter most for architects, engineers, and contractors. A parking lot photometric plan is often required for permits and inspections, and it must be prepared accurately to meet local lighting codes and safety standards. If you need a professional photometric plan, Stetra Lighting provides permit-ready calculations for parking lots and site lighting.
Looking for recommended parking lot light levels? See the existing table of maintained average, minimum and Avg:Min values by activity. Confirm the applicable criteria for your project before using these recommendations.
Why a Parking Lot Photometric Plan Matters
Most lighting issues in parking lots start with an incomplete or low-quality design. Once poles are installed, fixing dark spots, glare, or neighbor complaints becomes expensive. A proper photometric plan helps you catch problems on screen before they appear on site.
See Lighting Performance Before Construction
A photometric study lets you compare predicted light levels, uniformity and spill light before equipment is ordered. Review the actual fixture distribution in Stetra IES Studio, then use a project model to evaluate locations, heights, aiming and site boundaries.
- Confirm minimum and average foot-candle levels for drive lanes and parking stalls based on recommended foot-candle levels for parking lots.
- Review uniformity ratios so there are no harsh transitions between bright and dark zones.
- Check light trespass and glare at property lines, neighboring buildings, and roadways.
For owners, a clean photometric plan builds confidence that their parking lot will feel safe and easy to navigate at night. For designers, it is the technical proof that fixture selection, pole heights, and spacing are correct as part of professional lighting design services.
Parking Lot Light Levels and Uniformity Values
Parking lot light levels need a named source: a minimum, an average and a maximum describe different things. The table below lists recommended maintained values by activity, with the source and application identified. Confirm the criteria for your project location. 1 foot-candle (fc) = approximately 10.764 lux (lx).
Recommended Parking Lot Light Levels by Activity
The table below groups parking areas by activity and includes pedestrian use. It retains the maintained illuminance recommendations from Louisville-Jefferson County’s published Appendix 4D. These source-specific recommendations are not nationwide requirements or a reproduction of the latest IES criteria.
| Parking activity and typical uses | Average fc | Minimum fc | Avg:Min ratio |
|---|---|---|---|
| Low: neighborhood shopping, industrial employee, school and church parking | 0.8 | 0.2 | 4:1 |
| Medium: community shopping, office parks, hospital, airport and residential-complex parking | 2.4 | 0.6 | 4:1 |
| High: regional shopping centers, major athletic events, major cultural or civic centers, and fast-food facilities | 3.6 | 0.9 | 4:1 |
Source: Louisville-Jefferson County Land Development Code, Appendix 4D: Maintained Horizontal Illuminance Recommendations. The uniformity metric is average divided by minimum. The source’s separate vehicle-use-only values form a different calculation category and should not be substituted for these parking-and-pedestrian recommendations. Confirm the activity category, adopted criteria and maintained calculation assumptions for the actual project.
Select the criteria before designing: Confirm the applicable standard, local requirements, owner criteria and initial or maintained calculation basis. A parking lot can satisfy an average target while still failing its minimum or uniformity limit.
Worked Example: The Same Average, Different Uniformity
The following maintained calculation summaries are illustrative, not measurements from a Stetra project. Both layouts average 1.5 fc, but their darkest points differ.
| Metric | Layout A | Layout B |
|---|---|---|
| Average illuminance | 1.5 fc | 1.5 fc |
| Minimum illuminance | 0.5 fc | 0.1 fc |
| Maximum illuminance | 5.0 fc | 6.0 fc |
| Avg:Min = average ÷ minimum | 1.5 ÷ 0.5 = 3:1 | 1.5 ÷ 0.1 = 15:1 |
| Max:Min = maximum ÷ minimum | 5.0 ÷ 0.5 = 10:1 | 6.0 ÷ 0.1 = 60:1 |
Layout A has a higher minimum and lower Avg:Min and Max:Min ratios than Layout B, despite both layouts having the same average. Compare each result with the selected project criteria. This illustration does not establish code compliance or glare performance.
Lower values indicate more even lighting for Avg:Min and Max:Min. Always name the ratio: a 4:1 Avg:Min limit and a 4:1 Max:Min limit are different criteria. If the report uses U₀ = minimum ÷ average, a 4:1 Avg:Min limit corresponds to U₀ ≥ 0.25; higher U₀ indicates greater uniformity. See our lighting uniformity ratio guide for more explanation.
Request the average, minimum, maximum and named ratios for each required calculation area, together with the plane, grid spacing and light-loss assumptions. Check vertical illuminance, glare and property-line light separately where the project requires them.
Key Metrics in a Parking Lot Photometric Plan
Review the calculated levels and ratios for each defined area, using the units and calculation plane stated in the report. US site-lighting reports commonly express horizontal illuminance in foot-candles at a specified plane; confirm that plane rather than assuming every calculation is at grade.
- Average foot-candles (Avg FC) – the overall brightness level across the calculation area.
- Minimum foot-candles (Min FC) – the darkest points on the grid, critical for safety and visibility.
- Max FC – the highest calculated illuminance on the grid. Check glare separately from the surface-lighting summary.
- Uniformity ratios – typically Avg:Min and Max:Min, used by many standards and AHJs.
- Calculation areas – separate grids for parking bays, drive aisles, entrances, and sometimes walkways.
Many designers reference Illuminating Engineering Society guidance when setting targets, but the final criteria should always be checked against the project requirements and the authority having jurisdiction.
Uniformity Ratios, Light Levels, and Glare Control
Uniformity ratios describe how even the lighting is across the lot. A good parking lot photometric plan balances average and minimum illumination, contrast, glare control, and the criteria that apply to the specific site.
- Avg:Min ratio – compare the average-to-minimum result with the criterion selected for the application.
- Max:Min ratio – compare the highest and lowest values on the same grid and with the specified project criterion.
- Glare and BUG ratings – shielding, optics, cutoff, aiming, and BUG performance may be reviewed depending on the project and local ordinance.
| Check | Record in the plan | Why it matters |
|---|---|---|
| Lighting criteria | Applicable authority, owner requirements, source and edition. | Shows which criteria the design is being assessed against. |
| Calculation areas | Parking, drive aisles, paths and other required zones. | A whole-site average can hide a weak task area. |
| Plane and grid | Height, orientation, boundaries and point spacing. | Different grids can produce different summaries. |
| Fixture inputs | Exact model, optic, output, IES file, height and aiming. | Substitutions can change the results. |
| Light-loss basis | Initial or maintained results and the stated assumptions. | Alternatives need a consistent basis for comparison. |
| Summary | Average, minimum, maximum and named ratio for each grid. | Compare results with the selected criteria. |
| Boundaries | Required property-line locations, planes and limits. | Boundary checks are project-specific. |
| Glare and shielding | Relevant optics, aiming, shielding and separate glare checks. | Uniformity alone is not a glare test. |
Important: The checklist above documents the calculation basis. Use the recommended values by activity to review light levels and uniformity, then confirm the criteria that apply to your project with the authority having jurisdiction (AHJ).
The IES Lighting Library lists ANSI/IES RP-8-25 for roadway and parking facilities. Confirm the edition and criteria applicable to the project with the reviewing team. Numerical requirements should come from the applicable source and project brief, not from an uncited summary table.
What Should a Parking Lot Photometric Plan Include?
A professional parking lot photometric plan should clearly show both the lighting layout and the calculated performance of the proposed fixtures. For permitting and design review, the drawing should make it easy for the owner, contractor, engineer, and authority having jurisdiction to understand how the site will perform before installation.
A typical parking lot photometric plan may include:
- Fixture locations and pole locations showing where each luminaire will be installed.
- Fixture schedule identifying the manufacturer, model, lumen output, wattage, optics, CCT, mounting height, and other relevant specifications.
- Point-by-point foot-candle calculations showing the predicted illumination throughout the parking area, drive aisles, pedestrian routes, entrances, and other required zones.
- Minimum, maximum, and average light levels for each calculation area.
- Uniformity ratios, such as Avg:Min and Max:Min, where required.
- Property-line calculations to evaluate light trespass onto neighboring properties.
- Iso-footcandle contours or false-color analysis when useful for showing how the light is distributed across the site.
- Glare and spill-light considerations, including shielding, fixture distribution, BUG ratings, and aiming where applicable.
- Project notes and design assumptions such as mounting heights, calculation-plane height, fixture output, and applicable local requirements.
The exact information required varies from project to project. For permit submissions, the local municipality or authority having jurisdiction should always be checked before the final calculation is issued.
What to send for a parking lot study
Send a scaled site plan, project city and state, fixture models and IES files if selected, pole heights, known property-line constraints, and any reviewer comments. Include the required delivery date so the scope and schedule can be confirmed. Review photometric plan cost factors and Stetra’s parking lot photometric examples before requesting a quote.
At Stetra Lighting, we prepare parking lot photometric plans using manufacturer photometric data and project-specific site information so the lighting layout can be evaluated before poles and fixtures are installed.
When Stetra Lighting prepares a parking lot photometric plan, we test several layouts and distribution types. The goal is to meet project standards with as few poles as practical while keeping the site comfortable, legible, and neighbor-friendly.
For a broader explanation of the drawing itself, see our guide to what a photometric plan is. If you need to review an existing plan, use our step-by-step guide on how to read a photometric plan.
How to Review a Revised Parking Lot Layout
When a layout shows dark corners or excessive contrast, compare the original and revised calculations on the same basis. Check the following items before treating a change as an improvement:
- Inputs: Confirm the fixture family, optics, mounting heights, site geometry, grid and light-loss assumptions for both options.
- Weak areas: Locate the low points and transitions that prompted the revision; do not assess only the average.
- Calculated results: Compare the minimum, average, maximum, uniformity and relevant boundary values for each required area.
- Equipment and energy: Record fixture count, input power and operating assumptions before claiming an energy or cost saving.
Record the design change and the corresponding calculation output together. For worked project examples, use the linked parking lot case studies; do not reuse another site’s criteria as a universal requirement.
For a dealership example, where the display lot needs brighter and more even light than customer parking, see our car dealership photometric plan.
Key Takeaways for Parking Lot Photometric Plans
A strong parking lot design starts with a clear, well-documented photometric plan. When you understand light levels, uniformity ratios, and how fixtures actually distribute light on the ground, you avoid surprises after installation.
| Before approving | Check | Next step if unclear |
|---|---|---|
| Inputs match the project | Fixture schedule, IES data, height and aiming agree. | Resolve differences before using the results. |
| Criteria are traceable | The report identifies the applicable source and project assumptions. | Confirm the criteria with the reviewing team. |
| All required areas are covered | Task areas and required boundaries have suitable grids. | Request the missing calculation coverage. |
| Results can be compared | Plane, grid and initial/maintained basis are consistent. | Recalculate or label differences clearly. |
| Submittal is coordinated | Notes, drawings and selected equipment agree. | Document revisions and any remaining review requirements. |
Before you order fixtures or pour foundations, make sure your parking lot photometric plan has the right targets, ratios, and calculations in place. If you need support, Stetra Lighting can prepare a professional, permit-ready design tailored to your site, fixtures, and local requirements.