Inputs
Example Data Table
| Item | Value | Unit/Note |
|---|---|---|
| Load width | 3.20 | m |
| Load height | 4.10 | m |
| Trailer deck height | 1.20 | m |
| Overhead obstruction height | 5.80 | m |
| Roadway width | 7.30 | m |
| Curve radius | 60 | m |
| Computed total height | 5.45 | m (deck + load + tie-down) |
| Required vertical clearance | 5.70 | m (adds dynamic + safety) |
| Vertical margin | 0.10 | m (pass if ≥ 0) |
| Required straight width | 3.90 | m (adds side + sway) |
| Straight margin | 3.40 | m (using roadway width) |
Formula Used
How to Use This Calculator
- Measure the load width and height at the widest and highest points.
- Add trailer deck height and tie-down/cribbing thickness to build total height.
- Enter the lowest overhead clearance on the route segment being checked.
- Select roadway or lane width, depending on permits and traffic control.
- Set conservative allowances for lateral sway and vertical bounce.
- For tight turns, enter the smallest curve radius and vehicle wheelbase.
- Click Calculate Clearance and review PASS/FAIL margins.
- Use CSV/PDF export for permitting packages and briefings.
Professional Notes for Transport Clearance Planning
This short article explains how to interpret the calculator outputs and apply them to route screening and permitting.
1) Define the transport envelope
Clearance assessment starts with the true transport envelope, not just the equipment nameplate. The calculator builds Total Height from deck height, load height, and tie-down allowance, then adds dynamic and safety margins. For example, a 4.10 m load on a 1.20 m deck with 0.15 m tie-down produces a 5.45 m transport height before allowances.
2) Verify the governing vertical constraint
The lowest overhead feature controls the route: bridges, gantries, sign trusses, temporary scaffolds, and utility crossings. Enter the smallest measured obstruction height for the segment being reviewed. A positive margin indicates workable clearance, while a negative margin means the move requires rerouting, lowering the load, or controlled lifting of obstacles by authorized crews.
3) Check straight-line lateral clearance
Lateral checks compare the available width (roadway or lane basis) against the required width that includes side clearance and lateral sway. In practice, sway allowance covers suspension movement, steering wander, and minor positioning error. When margins are tight, treat shoulders, barriers, and kerbs as hard limits unless the permit explicitly authorizes encroachment.
4) Include curve swept-path effects
Tight curves can be more restrictive than straight sections. The calculator estimates low-speed swept width by adding inside offtracking (wheelbase² / 2R) and outside swing (front overhang² / 2R). With a 6.50 m wheelbase and 60 m radius, offtracking is about 0.352 m, which can materially change lane control needs.
5) Turn results into a route decision
Use the PASS/FAIL badges as an initial screen, then document the controlling segment and mitigation. Common actions include escort positioning, lane closures, timing windows, speed restrictions, and field verification. Export the CSV or PDF and attach it to permit submissions, toolbox talks, and stakeholder briefings so everyone understands the assumed clearances and allowances.
FAQs
1) What does “margin” mean in the results?
A margin is available minus required clearance. Positive means your inputs pass for that segment. Negative means you need route changes, smaller transport dimensions, or approved mitigation measures.
2) Should I use roadway width or lane width?
Use lane width when you must stay within one lane. Use roadway width when the permit and traffic control allow occupying multiple lanes or the full paved width.
3) Why add vertical dynamic and safety allowances?
Real moves include bounce, pavement irregularities, and measurement uncertainty. Allowances create a conservative envelope so you do not plan to “just fit” under an obstruction.
4) The curve result shows N/A. What does that mean?
N/A means the curve radius was not provided, so swept-path effects were skipped. Enter the smallest curve radius on the route to evaluate offtracking and outside swing.
5) Is the curve model accurate for all vehicles?
It is a practical low-speed approximation for screening. Complex multi-axle or steerable trailers may behave differently. For critical moves, validate with swept-path software and field checks.
6) Can this replace field measurement?
No. Use it to standardize calculations and document assumptions. Always confirm critical obstructions, temporary works, and roadway restrictions with on-site measurement and authority approvals.
7) What is a good workflow for permit packages?
Run the calculator per route segment, save outputs, and export CSV/PDF. Add drawings, photos, and mitigation steps. Submit the package with a clear list of controlling constraints and responsibilities.