Example Data Table
| Scenario | Total Load | Length | Setback | Spread Width | Impact | Safety | Curb Capacity |
|---|---|---|---|---|---|---|---|
| Pallet staging | 60 kN | 4.0 m | 0.5 m | 1.2 m | 1.10 | 1.50 | 22 kN/m |
| Small equipment share | 110 kN | 6.0 m | 0.8 m | 1.5 m | 1.20 | 1.60 | 28 kN/m |
| High-impact handling | 90 kN | 3.0 m | 0.4 m | 1.0 m | 1.35 | 1.75 | 25 kN/m |
Formula Used
- Convert to line load: qline = (W × IF) ÷ L
- Setback spreading: SFspread = 1 + (S ÷ B)
- Effective curb load: qeff = qline ÷ SFspread
- Allowable: qallow = C ÷ SF
- Utilization: U% = (qeff ÷ qallow) × 100
- W=load, IF=impact factor, L=length, S=setback, B=spread width, C=capacity, SF=safety factor.
How to Use This Calculator
- Enter the total staged load and select its unit.
- Measure the contact length parallel to the curb.
- Measure setback from the curb face to the load center.
- Set a realistic spread width for mats or footprints.
- Choose impact and safety factors for your activity.
- Enter the curb line-load capacity from your project rule.
- Press Calculate to see utilization and required adjustments.
- Use CSV or PDF downloads for site communication.
Why Curbside Loading Controls Matter
Curb edges are not designed for unlimited storage. Concentrated staging can crack curbs, disturb bedding, and create trip hazards for pedestrians. Treat curbside areas as temporary working zones with defined capacities. When you quantify loading, you can plan smaller drops safely, longer staging lines, or more setback, reducing peak demand. This calculator reports utilization so crews can see whether a setup is within an agreed limit.
Turning Vehicle and Material Loads Into Line Load
Field planning often starts with a total load: pallets, bundled rebar, or a portion of a delivery truck. The calculator converts that total into a line load by dividing by contact length. For example, 80 kN spread over 4 m is 20 kN/m before factors. A longer contact line reduces stress, when using dunnage or mats to increase bearing length.
Setback and Distribution Width Effects
Loads placed away from the curb face spread through base and pavement before reaching the curb. The spreading factor uses setback and an assumed distribution width to reduce the effective line load. Increasing setback from 0.3 m to 0.9 m can lower demand when the spread width is about 1.2 m. Use realistic widths: narrow wheels behave differently than wide timber mats.
Choosing Impact and Safety Factors
Impact factors capture bumps, placement drops, and vehicle braking. Typical planning values range from 1.05 for steady placement to 1.35 for rough handling. Safety factors add margin for unknowns such as voids, weak subgrade, or uneven contact. Many site rules fall between 1.3 and 2.0. If you lack a verified curb rating, increase the safety factor and confirm with engineering.
Documenting Results for Site Coordination
Clear documentation prevents rework. Export a CSV to log multiple scenarios and a PDF to attach to permits, traffic plans, or toolbox talks. Record the load source, measured contact length, setback, and the capacity basis used. If utilization exceeds 100%, the calculator suggests a required length or setback so teams can adjust without guessing.
FAQs
What does “line load” mean in this calculator?
Line load is the load per unit length along the curb contact. The tool converts your total staged load into kN/m using the contact length, then applies impact and setback spreading before comparing to the allowable capacity.
How do I estimate contact length for stacked materials?
Use the length of the footprint parallel to the curb, including dunnage or mats. If pallets are staged end-to-end, add their lengths. When in doubt, measure the planned layout on the ground.
What spread width should I enter?
Use the effective width that distributes load toward the curb: mat width, skid width, or the width of the load base. Wider distribution reduces effective demand. Avoid optimistic widths that do not match the actual support.
How should I choose an impact factor?
Use 1.05–1.15 for controlled placement and low traffic. Increase toward 1.25–1.35 for rough handling, braking, or bumps near the curb. If you cannot control operations, assume a higher value.
Where do I get curb capacity values?
Use the project’s temporary works criteria, local authority guidance, or an engineer’s curb/pavement assessment. If you only have a conservative site rule, enter that number and apply an appropriate safety factor.
What if the utilization is over 100%?
Reduce staged load, increase contact length, or increase setback to improve spreading. The tool also estimates the length or setback needed to meet the allowable. If limits are tight, consult engineering for alternatives.
Important Notes
- This is a screening check, not a substitute for engineering design.
- Confirm local restrictions, permits, and utility clearances before staging.
- If conditions are uncertain, increase the safety factor and re-check.