If your tender submission includes a DIALux/Relux report, optics choice behind the IES/LDT file is one of the fastest ways to get flagged.
Most “wrong optics” problems are not about wattage—they are about:
- wrong distribution type (Type II vs Type III vs Type IV)
- wrong mounting height / spacing assumptions
- missing maintained factor (day-one numbers only)
- broken traceability (BOQ ↔ IES ↔ DIALux cannot be audited)
✅ Start here (IES/LDT evidence hub)
✅ Need the full tender pack in 24H
Quick Answer (3 lines)
- Pick Type II/III/IV by road geometry (width + pole position), then prove it in DIALux/Relux.
- Run a spacing sanity check before you promise spacing.
- Submit a traceable chain: BOQ line → model/optic → IES/LDT filename → DIALux reference.
Need the full tender submission pack checklist (BOQ + IES + attachments)?
→ Solar Street Lighting Tender Pack Checklist →
A real tender failure we see (anonymous)
One EPC submission was delayed because the design used a Type II optic on a roadway that required wider lateral coverage.
The reviewer re-ran the same geometry and found a dark band near the lane centerline, so the team had to redo optics selection and update the IES + report pack under a tight deadline.
Lesson: optics type is not a label—it must match road width, pole position, and maintained assumptions.
Why optics mistakes trigger tender rejection
1) Uniformity fails first (not average lux)
Even if average lux looks acceptable, the wrong distribution often creates dark zones, causing:
- minimum illuminance failure
- poor uniformity ratio failure
- hotspot/glare concerns
2) “IES file mismatch” is an audit-trail problem
Reviewers don’t just ask “is it bright enough?”
They ask: Can I audit BOQ item → product → optic → IES/LDT file → DIALux outputs?
If any link is missing, they label the submission non-traceable.
What Type II / III / IV actually means (simple, field-friendly)
Roadway lateral distribution patterns are commonly designated as Types I–V. For edge-mounted roadway luminaires, the practical descriptions are:
- Type II: narrow streets
- Type III: streets of medium width
- Type IV: wide street applications
Important: do not pick optics by label alone. Use the label as a starting point, then confirm with geometry + DIALux.
Visual (recommended)
Add a simple beam pattern image so non-photometric reviewers can understand instantly.
Type II vs Type III vs Type IV roadway lighting distribution diagram lateral coverage comparison
Beam pattern comparison for edge-mounted roadway luminaires (visual aid—always verify in DIALux/Relux)
Quick comparison table
| Feature | Type II | Type III | Type IV |
|---|---|---|---|
| Best for | Narrow roads / walkways | Standard roads (common edge-mounted) | Wide streets / forward throw |
| Lateral coverage | Narrow-to-medium | Medium | Wide |
| Common risk if misused | Dark lanes on wider roads | Spill/hotspots if too wide | Glare/spill if not controlled |
| Must verify with | DIALux/Relux + real geometry | DIALux/Relux + real geometry | DIALux/Relux + tilt + spill limits |
A tender-safe decision method (Geometry → Optics → IES/LDT → DIALux)
Step 1 — Lock the geometry (no guessing)
Collect:
- roadway width (W), lane count
- pole position (edge / median / setback)
- mounting height (H), arm length/overhang
- target criteria (avg/min/uniformity)
- tilt limit (0° unless tender allows otherwise)
Step 2 — Choose candidate optics (Type II/III/IV)
Start with Type descriptions and shortlist 1–2 optics for comparison.
Step 3 — Run a spacing sanity check (before DIALux)
Spacing is constrained by optics + geometry; use a quick sanity check before committing to tender drawings.
Spacing is not a sales promise. Use a sanity check early.
Red flag rule:
If your proposal needs spacing far beyond typical practice for the same mounting height, expect reviewer questions unless your photometry and uniformity prove otherwise.
(We document spacing assumptions and the evidence chain on the IES/LDT hub page: /engineering-support/ies-photometric-files/)
Step 4 — Model “maintained”, not day-one
A tender-safe report states maintained factors clearly (LLD/LDD or maintenance factor). If maintained assumptions are missing, the design looks like “marketing lux.”
Maintained factors that reviewers recognize (LLD + LDD)
State maintained assumptions in tender packs to avoid “day-one only” objections.
Maintained lighting is what matters in acceptance and long-term compliance.
A practical roadway design reference uses:
- LLD = 0.90
- LDD = 0.90
- combined factor 0.81
- representing about 28% loss from initial to maintained output
Your tender pack should state these assumptions (or your justified alternatives) and show where they were applied.
Data example: Why spacing is not arbitrary
A classic spacing example calculates maximum spacing using:
- LL, CU, LLD, LDD, Eh, W
and yields a numerical spacing value (then uniformity must still be checked).
Key takeaway:
Spacing comes from photometry + maintained factors + target illuminance, and uniformity is then verified by photometric diagrams/software outputs.
Tender reviewer checklist: 7 “pass/fail” items
Reviewers typically verify the IES/LDT file name and maintained assumptions inside the report before accepting results
1) IES/LDT filename matches quoted model + optic + power package
2) Type II/III/IV choice matches road width + pole position
3) Mounting height/arm/spacing match drawings
4) Tilt stated and consistent (default 0° unless specified)
5) Maintained factors stated (LLD/LDD or MF)
6) DIALux/Relux report references the exact IES/LDT file used
7) BOQ mapping shows an audit trail:
BOQ line → model code → IES/LDT filename → DIALux page/reference
✅ Use this engineering support page as your tender “evidence hub”
A simple audit trail prevents “IES mismatch” claims and accelerates tender approval.
Common tender rejection reasons (and how to prevent them)
Wrong distribution type
- Symptom: minimum lux/uniformity fails after reviewer re-check
- Fix: compare Type II vs III vs IV under the same geometry and include a 1-page comparison summary.
File mismatch (model/optic/power)
- Symptom: reviewer says IES does not match BOQ or datasheet
- Fix: enforce file naming + provide a photometry index table.
Spacing too aggressive
- Symptom: hotspots and dark zones, uniformity fails
- Fix: document spacing assumptions, apply maintained factors, and show the audit trail.
Missing maintained factor
- Symptom: “day-one only” suspicion
- Fix: show LLD/LDD (or MF) and keep targets maintained.
What to submit (Minimal “Audit Trail Pack”)
If you want reviewers to approve faster, submit:
- IES/LDT files (by model + optic)
- DIALux/Relux report (lux + uniformity + layout proof)
- BOQ mapping table (item → file → report)
- 1-page reviewer notes (geometry + maintained assumptions)
✅ Get the pack structure / template here
Or request it in 24H →
Internal links (Related tender resources)
- Tender Documents & BOQ →
- IES Photometric Files →
- DIALux Simulation Outputs →
- Lighting Design Service →
CTA (End)
If your tender is urgent, send any of the following and we can start:
- road width + pole height/spacing range
- tender targets (avg/min/uniformity)
- drawings, BOQ, or site photos
✅ Request Engineering Pack (24H) →
