Quick Answer
Lighting Maintenance Factor (MF) is the depreciation allowance used in road lighting design. It converts “day-one” illuminance into maintained illuminance—so your road still meets the required lux/uniformity after LED aging, dirt, and failures, not only on commissioning day.
✅ If you are preparing an EPC/government submission and need an audit-ready deliverables pack (DIALux/Relux PDF report + IES/LDT files + BOQ mapping), request here:
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What’s Inside a Tender-Ready Deliverables Pack (1 Table)
| Deliverable | What reviewers check | Most common failure |
|---|---|---|
| BOQ + mapping | Model/qty/specs are traceable | BOQ cannot map to IES/DIALux |
| IES/LDT photometric files | Exact model + optics + tilt | Generic / wrong optics / wrong mounting |
| DIALux/Relux report (PDF) | Lux + uniformity + layout proof | MF/assumptions missing |
| Datasheets & drawings | Spec proof + install feasibility | Missing attachments / unclear mounting |
Note: final criteria always follow the tender-stated standard and reporting format (e.g., EN 13201 or IESNA RP-8).
Who This Guide Is For (Road Projects)
Use this guide if you are:
- Reviewing a roadway / municipal / area lighting design and want results that still hold after depreciation.
- Doing DIALux/Relux calculations and need a defensible MF assumption for approval.
- Preparing an EPC/government submission and want to avoid rejection + redesign loops.
- Comparing suppliers and need audit-proof logic, not marketing claims.
What the Maintenance Factor Means (Road Lighting)
Maintenance Factor (MF) is the ratio of maintained illuminance to initial illuminance.
It indicates how much light remains after time-dependent losses: LED lumen depreciation, dirt accumulation on optics, and component failures.
Road projects fail acceptance not because “the calculation is wrong,” but because MF is set unrealistically (or not documented). In tender submissions, MF must be:
- stated clearly in the report,
- consistent with environment + maintenance plan,
- traceable to luminaire choice and expected field conditions.
Design Basis & Standards (Audit-Friendly)
We follow the tender-stated standard first. If the tender does not specify, road lighting submissions commonly align to accepted roadway references such as:
- EN 13201 (Road lighting, Europe) — lighting classes, calculation grids, evaluation metrics.
- IESNA RP-8 (Roadway lighting, North America) — roadway lighting practice and evaluation approach.
In every DIALux/Relux report we document:
- Target criteria (lux/uniformity/glare if required)
- Geometry inputs (road width, lanes, pole height, spacing, arm length, tilt)
- Calculation settings (MF, grid, surface assumptions)
- Photometric reference (IES/LDT file name + model/optics mapping)
- Pass/Fail summary against the criteria
MF Formula for Road Lighting (No Confusion)
For road lighting, MF is normally expressed as:
MF = LLMF × LMF × LSF
Where:
- LLMF (Lamp Lumen Maintenance Factor): LED lumen depreciation over time (thermal + driver stability impacts).
- LMF (Luminaire Maintenance Factor): dirt/dust/insect ingress reducing optical transmission between cleanings.
- LSF (Lamp Survival Factor): percentage of luminaires still operating (driver/wiring/environment failures).
Note: RSMF (room surface maintenance factor) mainly applies to enclosed indoor spaces. For roadway projects it is typically not used—unless the tender explicitly requires a room-like reflectance assumption.
Typical MF Values for Road Lighting (Quick Table)
These are practical ranges used to avoid over-optimistic designs. Your final MF should reflect environment + cleaning plan + luminaire sealing.
| Road environment | Typical maintenance reality | Typical MF range |
|---|---|---|
| Clean urban roads (planned cleaning) | low dust, regular maintenance | 0.80 – 0.90 |
| Normal roads (mixed traffic + seasonal dust) | periodic cleaning | 0.75 – 0.85 |
| Dusty roads / industrial outskirts | heavy dust, limited cleaning | 0.65 – 0.80 |
| Coastal roads (salt + dirt + humidity cycles) | higher optical soiling risk | 0.65 – 0.80 |
Audit note: reviewers will ask “What cleaning interval and luminaire protection level does this MF assume?”
State it in one sentence in the report.
Worked Example (Maintained Lux vs Initial Lux)
If your target is maintained 20 lux and you choose:
LLMF = 0.90
LMF = 0.80
LSF = 0.95
MF = 0.90 × 0.80 × 0.95 = 0.684
So the required initial illuminance is approximately:
Initial ≈ Maintained / MF = 20 / 0.684 ≈ 29.2 lux
This is why “designing exactly to target on day one” often fails later.
Where to Set MF in DIALux/Relux (Step Guidance)
MF is set in the calculation / standards parameters of your project.
Exact menu labels vary by software version, but the principle is the same:
DIALux evo (typical path)
- Project / Standards / Calculation parameters → Maintenance factor (MF)
- Ensure the MF value is also printed in the exported PDF report (assumptions section).
Relux (typical path)
- Calculation settings → Maintenance factor (MF)
- Confirm the MF value appears in the report header/assumptions.
Tender tip: include a 1-line justification:
“MF = 0.75 based on dusty road environment + quarterly cleaning + IP66 optical chamber.”
Need an audit-ready DIALux/Relux report output set?
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How to Justify MF in Tender Review (Audit Notes)
A defensible MF statement references:
- Road environment (dust level / coastal humidity / industrial pollution)
- Cleaning interval (none / annual / quarterly)
- Luminaire sealing and optical chamber design (e.g., IP rating)
- LED lumen maintenance basis (e.g., L80/L90 claim with conditions)
- Failure allowance (driver reliability + warranty + service plan)
Most MF-related rejections are caused by missing assumptions and mismatch between BOQ, IES/LDT, and report.
Common reviewer red flags: - MF = 0.90 claimed for dusty roads with no cleaning plan
- “MF not stated” in the report (assumptions missing)
- BOQ model does not map to the exact IES/LDT used in the simulation
MF in Solar Road Lighting (Common Tender Failure Points)
MF disputes in solar road lighting tenders usually come from:
- Using generic IES files that don’t match actual optics or mounting tilt
- Not stating assumptions (MF, tilt, grid, road surface, spacing)
- “Marketing brightness” without traceable deliverables (IES + report + datasheet mapping)
That’s why we package submissions as:
BOQ mapping → IES/LDT references → DIALux/Relux report → datasheets/drawings
Start here if you need the full pack:
FAQ (Road Lighting)
1) What is a typical MF for road lighting?
It depends on dust level, coastal humidity, cleaning frequency, and luminaire sealing. In many road environments, 0.70–0.85 is typical.
2) MF vs LLMF — what’s the difference?
LLMF covers LED lumen depreciation over time. MF combines LLMF with dirt (LMF) and survival (LSF).
3) Why do tenders get rejected because of MF-related issues?
Usually because the submission is inconsistent: BOQ doesn’t map to IES, IES doesn’t match optics/tilt, or MF/assumptions are missing from the report.
Get a Tender-Ready Pack in 24H (CTA)
If you want to shorten review time and reduce redesign cycles, request a complete pack:
✅ BOQ mapping
✅ IES/LDT photometric files
✅ DIALux/Relux report (PDF)
✅ Datasheets + drawings
Request Engineering Deliverables (24H) →
