Quick Answer: What Is ANSI/IES RP-43-25?
ANSI/IES RP-43-25 is the Illuminating Engineering Society's 2025 Recommended Practice for Lighting Design for Outdoor Pedestrian Applications.
IES describes its purpose as providing pedestrian-oriented illumination recommendations for reassurance, safety, comfort, amenity and enjoyment in outdoor environments within lighting zones LZ-1 through LZ-4.
The intended audience includes lighting practitioners, architects, engineers and the general public.
What Changed in ANSI/IES RP-43-25?
The 2025 edition replaces RP-43-22 and expands the standard into a more comprehensive exterior-lighting resource. IES says the updated edition incorporates content from earlier IES material on quality lighting and environmental outdoor lighting.
Lighting Zones
Refined zone definitions help match the expected nighttime luminous environment to the actual setting.
Color
Color is explicitly included because nighttime visual quality cannot be described by illuminance alone.
Controls
Controls are part of the outdoor-lighting design discussion rather than an afterthought.
Glare Metrics
The current edition includes new glare content and a dedicated glare annex.
The published standard is 103 pages and includes main chapters plus annexes on illuminance recommendations, lighting-zone background, glare and temporal light modulation.
Lighting Zones LZ-1 Through LZ-4: Why They Matter
IES emphasizes that not all nighttime environments are the same. A quiet rural path, suburban commercial walkway and busy urban plaza should not automatically be designed to the same luminous character.
IES has continued educating designers and reviewers about the revised lighting-zone framework because it influences design decisions, light levels and responsible use of light at night.
RP-43-25 Starts With What Pedestrians Need to See
Outdoor pedestrians need more than enough light to see the pavement directly in front of them. Good pedestrian lighting can support orientation, wayfinding, recognition of other people, detection of terrain changes, comfort, reassurance and transitions between different brightness environments.
Glare Is a Core RP-43-25 Issue
The 2025 edition adds updated glare content and includes a dedicated annex on glare in outdoor applications. More lumens can actually reduce useful visibility when a bright source sits directly in the viewer's field of view.
Controlled Source
The person sees the path, people and surrounding objects without staring into a bright LED source.
Bright Source in the Eye
Measured illuminance can increase while contrast and visual comfort get worse.
For fixture-distribution terminology, see the Outdoor Lighting ANSI Standards Guide.
Environmental Considerations Are Built Into RP-43-25
The IES Outdoor Nighttime Environment Committee addresses pedestrian vision and glare along with nighttime environmental factors such as sky glow and wildlife preservation. RP-43-25 is therefore not simply about making outdoor spaces brighter.
- Does the light have a useful purpose?
- Is it aimed where the task occurs?
- Is output appropriate for the lighting zone?
- Can it be dimmed or shut off when not needed?
- Is unnecessary uplight or spill being created?
- Is the spectrum appropriate for the environment?
Controls Are Part of the Lighting Design
The 2025 edition explicitly includes controls among its updated content. The correct light level at 8:00 p.m. may not be the correct level at 3:00 a.m.
- Scheduled shutoff
- Late-night dimming
- Occupancy or activity response
- Zoned control
- Different event and normal-operation settings
Design principle: light should respond to actual nighttime need.
Color and Spectrum Matter More Than a CCT Number
The 2025 edition adds explicit color content. Color temperature is useful shorthand, but CCT alone does not fully describe a source's spectrum or how objects and people appear under it.
For outdoor pedestrian spaces, the useful question is not simply “2700K or 3000K?” It is whether the source supports the visual task, fits the nighttime setting and avoids unnecessary environmental impact.
Temporal Light Modulation: Why Flicker Appears in the Standard
RP-43-25 includes an annex on temporal light modulation, commonly called flicker. Modern LED systems can vary output rapidly because of driver or control behavior even when the variation is not obvious to every observer.
Its inclusion is another example of RP-43 moving beyond a simple “how many foot-candles?” approach to outdoor lighting quality.
RP-43-25 vs Electrical Code
RP-43 tells you how to think about quality and performance of outdoor pedestrian lighting. It does not tell you everything required to install the electrical system safely.
Lighting Performance
Pedestrian vision, glare, environment, lighting zones, controls and design.
Electrical Installation
Wiring methods, GFCI, grounding, burial, branch circuits and wet-location installation.
For installation rules, use the Landscape Lighting Electrical Code & Safety Guide.
RP-43-25 and ASHRAE 90.1 can affect the same exterior project, but they serve different purposes. RP-43 helps designers address pedestrian visibility, glare, lighting zones, and nighttime lighting quality, while Standard 90.1 controls energy use through exterior lighting power limits and automatic controls. Our ASHRAE 90.1 exterior lighting requirements guide explains how the energy-code side works and why a project may need to satisfy both standards rather than choosing one or the other.
RP-43-25 vs ADA Accessibility
RP-43 can help with pedestrian visibility, comfort and nighttime usability. ADA standards address physical accessibility such as accessible routes, ramps, parking, entrances, slopes and clearances.
A compliant accessible route can still have poor lighting, and a beautifully lit route can still be physically inaccessible. Strong site design handles both. See the School Campus Lighting Accessibility Guide and Parking Lot Lighting ADA Guide.
A Practical RP-43-25 Design Workflow
- Define nighttime use. Who is there, when, and what do they need to see?
- Identify the lighting zone.
- Map pedestrian tasks. Routes, entrances, faces, signs, hazards and destinations.
- Choose the minimum useful light.
- Control glare.
- Review environmental effects.
- Add controls.
- Check bright-to-dark transitions.
- Verify quantitative criteria in the official standard.
- Coordinate electrical compliance.
Common RP-43-25 Mistakes
Using the highest lighting zone to justify more light
The zone should describe the context, not be selected to support a desired fixture output.
Treating horizontal illuminance as the entire design
Pedestrian vision includes faces, objects, signs, terrain, adaptation and glare.
Ignoring glare because the photometric average looks good
A bright source can make the environment harder to see even when a meter reports adequate illuminance.
Running fixtures at full output all night
Controls are part of the current design framework.
Using RP-43 for roads without checking RP-8
Roadways and parking facilities are handled separately.
What This Guide Does Not Reproduce
ANSI/IES RP-43-25 is a copyrighted professional standard sold by the Illuminating Engineering Society. This page explains its scope, structure and design concepts in plain language, but it does not reproduce the standard's detailed illuminance tables, formulas, figures or copyrighted text.
For formal design or specification work, obtain the current standard directly from IES.
ANSI/IES RP-43-25 Chapter Map
↔ Swipe horizontally to see the complete map.
| Section | Topic | Practical Question |
|---|---|---|
| 1 | Introduction and Scope | Is this standard appropriate for the project? |
| 2 | Pedestrian Considerations | What does the person using this space need to see? |
| 3 | Visual Considerations | How do contrast, adaptation and glare affect performance? |
| 4 | Environmental Considerations | How can unnecessary nighttime impact be limited? |
| 5 | Five Principles for Responsible Outdoor Lighting | Is the light useful, targeted and appropriately controlled? |
| 6 | Community Planning | How should lighting fit the broader nighttime character? |
| 7 | Lighting Zones | What luminous environment is appropriate? |
| 8 | Outdoor Lighting Design Process | How should the project be worked through? |
| Annex A | Illuminance Recommendations | What quantitative recommendations apply? |
| Annex B | Lighting Zone Summary | How do zone definitions relate? |
| Annex C | Glare | How should glare be understood outdoors? |
| Annex D | Temporal Light Modulation | What role can flicker/modulation play? |
RP-43-25 vs RP-47-23 vs RP-8-25
↔ Swipe horizontally to compare standards.
| Standard | Primary Application | Good Fit For | Not the Main Standard For |
|---|---|---|---|
| ANSI/IES RP-43-25 | Outdoor pedestrian applications | Walkways, plazas, building approaches, pedestrian-oriented exterior spaces | Roadway design |
| ANSI/IES RP-47-23 | Landscape lighting | Landscape elements, gardens, plantings and landscape-lighting techniques | Roadway photometrics |
| ANSI/IES RP-8-25 | Roadway and parking facilities | Roads, intersections, parking lots, garages and vehicle-focused facilities | General landscape aesthetics |
A large site can use more than one standard. A campus may use RP-8 for parking areas, RP-43 for pedestrian paths and RP-47 for landscape-lighting features.
Official Sources Used for This Guide
ANSI/IES RP-43-25 FAQ
What does RP-43-25 stand for?
ANSI/IES RP-43-25 is Recommended Practice: Lighting Design for Outdoor Pedestrian Applications, published by the Illuminating Engineering Society in 2025.
What happened to RP-43-22?
RP-43-25 is the updated edition; IES identifies RP-43-22 as the previous edition.
What lighting zones does RP-43-25 use?
The standard uses LZ-1 through LZ-4 and includes refined definitions intended to better describe expected nighttime luminous environments.
Does RP-43-25 provide foot-candle recommendations?
IES identifies Annex A as containing illuminance recommendations. This page does not reproduce the copyrighted tables; obtain the official standard for exact project values.
Does RP-43-25 include glare?
Yes. The 2025 edition includes updated glare content and a dedicated annex discussing glare in outdoor applications.
Does RP-43-25 address flicker?
Yes. Annex D covers temporal light modulation, commonly referred to as flicker.
Is RP-43-25 for parking lots?
Pedestrian areas can overlap with parking sites, but roadway and parking-facility lighting is addressed more directly by ANSI/IES RP-8-25.
Is RP-43-25 legally required?
That depends on whether it has been incorporated into a law, ordinance, code, project specification, contract or other enforceable requirement.
Bottom Line
ANSI/IES RP-43-25 is best understood as a framework for designing outdoor places for people, not merely for light meters. Start with the pedestrian task and nighttime context, choose the correct lighting zone, control glare, consider environmental effects, use controls intelligently, and then verify the standard's quantitative recommendations. Pair RP-43 with the appropriate electrical code, product requirements and application-specific standards.