Example data table
| Design speed (km/h) | Auto height (mm) | Comfort limit (m/s²) | Profile | Estimated length (m) | Ramp each side (m) |
|---|---|---|---|---|---|
| 20 | 65 | 1.50 | Sinusoidal | 5.14 | 2.57 |
| 30 | 55 | 1.50 | Sinusoidal | 7.09 | 3.54 |
| 40 | 45 | 1.75 | Parabolic | 5.04 | 2.52 |
| 25 | 65 | 1.25 | Parabolic | 4.48 | 2.24 |
These examples use the same equations as the calculator and are not a substitute for local design requirements.
Formula used
The calculator estimates vertical acceleration using the road profile curvature and travel speed. With speed v, height h, and length L:
- Sinusoidal hump: a ≈ (2π² · h · v²) / L²
- Parabolic hump: a ≈ (8 · h · v²) / L²
In Design mode, the calculator solves for L (or h if a target length is given) using the selected comfort limit a. This is a simplified estimator and should be checked against project specifications and site conditions.
How to use this calculator
- Select Design to size a new hump, or Check to evaluate an existing one.
- Pick a profile and enter a comfort limit to match the project’s traffic calming goal.
- Enter design speed; in Check mode you may leave speed empty to estimate comfort speed.
- Provide height or length if you already have a constraint from the site layout.
- Enter lane geometry to generate a crossing width note for marking and setting-out.
- Press Calculate to view results above the form, then export CSV or PDF.
Always confirm signage, drainage, visibility, emergency access, and local authority standards before construction.
Professional notes for speed hump dimensions
1) Purpose and performance targets
Speed humps are used to reduce operating speeds on local streets and within controlled sites. A practical target is to slow typical passenger vehicles to a chosen design speed (often 15–40 km/h), while keeping ride comfort acceptable. This calculator uses a comfort limit in m/s² to translate the target speed into workable height and length.
2) Profile and comfort relationship
Profile shape affects curvature and therefore vertical acceleration. Sinusoidal shapes generally distribute curvature smoothly, while parabolic shapes are simpler to set out. The calculator applies a profile constant K to estimate acceleration using a ≈ (K · h · v²) / L², where h is height (m), v is speed (m/s), and L is length (m).
3) Typical dimension ranges
For preliminary planning, hump heights commonly fall between 40–80 mm, with total lengths roughly 3.0–4.5 m for urban calming. Lower heights may be appropriate for sensitive routes; higher heights increase the calming effect but can increase noise and discomfort. Always verify that drainage paths remain clear and that the hump does not trap water at the gutter line.
4) Site geometry and construction notes
Crossing width should cover the traveled way and any intended shoulders, and side tapers may be required near channels to protect drainage. Markings and signs should be placed to maintain visibility in day and night conditions. Where heavy vehicles are frequent, confirm that the selected length and profile do not cause excessive chassis strike risk.
5) Quality checks and documentation
After installation, measure height at the crown and length along the centerline, then compare against the planned values. Small deviations can change comfort noticeably because acceleration varies with h/L². Keep records for inspection: as-built dimensions, location chainage, pavement condition, and signage/marking completion, then export results for field packages.
FAQs
1) What comfort limit should I use?
For preliminary checks, 1.0–2.5 m/s² is commonly used for passenger comfort. Use a lower value for sensitive routes and a higher value for stronger calming. Confirm your agency or client criteria.
2) Should I choose sinusoidal or parabolic?
Sinusoidal profiles typically feel smoother at the same height and length. Parabolic profiles are easy to set out and can be compact. Use the profile that matches your detailing and local practice.
3) Why does length change so much with speed?
Vertical acceleration scales with speed squared. If speed increases, the hump must be longer or lower to maintain the same comfort. That’s why design speed is a critical input.
4) What if I know the available length on site?
Enter the target length in Design mode. The calculator will estimate the height needed to meet the comfort limit at the chosen speed. Review warnings if the computed height is unusually high or low.
5) How do lane width and shoulders affect the result?
They do not change the height–length calculation, but they affect crossing width notes for layout and markings. Use them to document the full hump extent across the traveled way.
6) Can this replace local standards?
No. It is an estimator for preliminary sizing and checking. Always confirm geometry, signing, markings, drainage, accessibility, and emergency access requirements using the applicable local guidance and approvals.
7) Does this account for vehicle suspension differences?
Not directly. The model uses a simplified acceleration relationship. Actual ride response varies by vehicle type, speed variation, tire pressure, and pavement stiffness. Use field trials or agency guidance for final tuning.