Roadway Lighting Design Calculator

Roadway Lighting Inputs

Calculation mode

Arrangement type

Road length (m)

Road width (m)

Number of lanes

Target average illuminance (lux)

Proposed spacing (m)

Used only for evaluation mode.

Luminaire lumens

Luminaire wattage (W)

Utilization factor

Maintenance factor

Mounting height (m)

Luminaires per pole

Operating hours per day

Electricity rate per kWh

Reset

Formula Used

1) Recommended spacing for target design
S = (n × Φ × CU × MF) / (E × W)

2) Actual average illuminance
Eavg = (n × Φ × CU × MF) / (W × Sactual)

3) Pole count along the road
Positions = ceil(L / S) + 1

4) Installed load
kW = (Total luminaires × Wattage) / 1000

5) Annual energy
Annual kWh = Installed kW × Hours per day × 365

6) Annual cost
Cost = Annual kWh × Electricity rate

Here, n is the effective number of luminaires per spacing interval, Φ is luminaire lumen output, CU is utilization factor, MF is maintenance factor, E is target illuminance, W is roadway width, L is road length, and S is spacing. Uniformity is shown as a planning estimate from spacing-to-height ratio. Final designs should use photometric files and local standards.

How to Use This Calculator

Choose whether you want a new design or an existing spacing check.
Enter roadway length, width, lane count, and target illuminance.
Fill in luminaire lumens, wattage, utilization factor, and maintenance factor.
Set mounting height, arrangement type, and luminaires per pole.
Enter operating hours and electricity rate for energy estimates.
Click Calculate Design to place the result block above the form.
Review spacing, illuminance, pole count, power, and annual cost.
Use the CSV or PDF buttons to export the result summary.

Example Data Table

Road Length (m)	Road Width (m)	Arrangement	Lumens	CU	MF	Target Lux	Recommended Spacing (m)	Actual Lux	Total Supports
1000	12	Single side	28000	0.38	0.80	20	35.47	20.57	30

Frequently Asked Questions

1. What does this calculator estimate?

It estimates spacing, pole count, luminaires, average illuminance, energy demand, annual energy use, annual cost, and a preliminary uniformity indicator for roadway layouts.

2. Is this enough for a final lighting specification?

No. It is a preliminary engineering tool. Final approval should use manufacturer photometric files, local roadway classes, glare checks, and any required lighting standard.

3. What is the utilization factor?

Utilization factor is the share of emitted lumens that effectively reaches the target road surface. It depends on optics, geometry, road width, and mounting arrangement.

4. What is the maintenance factor?

Maintenance factor accounts for lumen depreciation, dirt, aging, and real operating losses. Lower values make designs more conservative and closer to maintained conditions.

5. Why does opposite arrangement increase support count?

Opposite layouts place poles on both sides at the same station. That doubles supports for each spacing interval and often improves coverage and transverse light balance.

6. Why is spacing-to-height ratio important?

It is a quick indicator of distribution quality. Very large spacing relative to mounting height often produces darker gaps and weaker uniformity between luminaires.

7. Can I use this for LED or other light sources?

Yes. Enter the actual luminaire lumen output and wattage for the selected fixture. The calculator is source-neutral when reliable input data is available.

8. What should I verify before installation?

Verify pole setbacks, foundations, wind loading, optics, glare limits, road classification, dimming strategy, circuit design, and local code or agency requirements.