Long story short, followed by a long analysis.
They installed speed bumps in La Ecovilla. People donated their time and worked on it, ****which is always appreciated.
But ...
The bumps' curvature is wrong. They force cars to a full stop, instead of allowing the flow of traffic. They cause sound and air pollution at the same time.
They are not painted, so depending on the time of day bland too much into the environment. Cars hit them accidentally, which is an accident waiting to happen.
Since no one wants to hit them with 2 wheels at the same time, they force one car into the middle, creating choke-points on the otherwise 2-lane streets.
I threw some research agents at it, and this is what I got.
(Agents: Hermes, mix of Kimi-k2.6 and GLM-5.1 open source, cloud - this is not ChatGPT slop copy pasted, agents churned on it for 15 minutes and collected that was asked for.)
They have gathered sufficient technical data from engineering standards, peer-reviewed literature, and design guides. Here is a synthesis of the research on optimal speed hump geometry for 15 km/h flowing traffic.
Executive Summary
For 15 km/h (≈4.2 m/s) flowing traffic, the optimal device is technically on the boundary between a speed bump (parking-lot style, abrupt) and a short speed hump (street style, gradual). Because you specified flowing traffic — implying continuous movement without a full stop — the design should be a low-amplitude, sinusoidal or parabolic profile rather than a steep parking-lot bump. A standard speed bump at this speed would force an uncomfortable stop-start motion; a properly dimensioned hump can maintain ~15 km/h flow while still providing vertical deflection.
1. Dimensional Design Parameters for ~15 km/h
2. Profile Shape Analysis
Research (D'Apuzzo 2023, Alshabibi 2025, Ewing) identifies four fundamental cross-sections:
Key research finding: Chandra & Sekhar (2022, Transport) found that the average speed difference between circular and parabolic humps is ~15 km/h — confirming that profile shape alone can shift target speeds by this magnitude. For 15 km/h, parabolic is strongly preferred over circular.
Mathematical formulation for a sinusoidal profile:
$$y(x) = \frac{H}{2}\left(1 - \cos\left(\frac{2\pi x}{W}\right)\right)$$
Where:
- $H$ = 0.05 m (50 mm)
- $W$ = 2.0 m (total traverse width)
This yields a maximum slope angle of ~8.9° and a peak vertical acceleration well within ISO 2631 ride comfort limits at 15 km/h.
3. Vehicle Dynamics Considerations
At 15 km/h ($v = 4.17$ m/s), the critical dynamic constraints are:
- Vertical acceleration: Should remain under ~1.5–2.0 m/s² (0.15–0.2 g) for passenger comfort. A 50 mm sinusoidal hump over 2.0 m produces ~1.2 m/s² peak vertical acceleration.
- Suspension compression: Standard passenger car suspension (natural freq ~1.2–1.5 Hz) can absorb this without bottoming.
- Ground clearance: Low-clearance vehicles (sports cars, lowered suspensions) require the approach/departure ramps to be flush with the road surface — avoid sharp edges.
4. Standards & Guidelines Cross-Reference
Conclusion: To achieve 15 km/h with flowing traffic, you need a profile that is shorter and slightly steeper than a standard street hump, but much longer and lower than a parking-lot bump. The 50 mm height is the sweet spot.
5. Recommended Optimal Design for 15 km/h Flow
Based on the synthesis of the above research, the optimal geometry is:
Why this works: The 50 mm height provides enough vertical deflection that drivers perceive the need to slow, but the 2.0+ m sinusoidal width ensures the slope is gentle enough to traverse at 15 km/h without stopping. A circular profile with these same dimensions would produce a speed closer to 25 km/h (per Chandra's 15 km/h delta finding); the sinusoidal/parabolic profile "absorbs" that difference and brings the target speed down to the desired 15 km/h while preserving ride quality.
6. Additional Considerations
- Spacing: If multiple humps are used, spacing should be 20–40 m apart to maintain the 15 km/h corridor average (per FHWA and Auckland Transport guidelines).
- Drainage: Maintain cross-slope or provide gaps to prevent ponding.
- Emergency vehicles: At 15 km/h, even ambulances with patient loads can traverse a 50 mm sinusoidal hump safely; no special gaps required.
- Snow plows: Flat-topped or very low-slope transitions at the edges help plow blade clearance.
Sources consulted: D'Apuzzo et al. (2023, Sustainability); Alshabibi (2025, Infrastructures); Chandra & Sekhar (2022, ICE Transport); ITE Speed Hump Guide; NACTO Urban Street Design Guide; FHWA Traffic Calming ePrimer; Ewing traffic calming literature; Wikipedia engineering summaries; Vanguard Group NZ; Auckland Transport Engineering Design Code.
Still here? Fell asleep?
All right. Here is the
SOLUTION
Add some material to the existing ones. Make them longer (following the documents) so they are not stopping, but slowing traffic.
Make them as wide as the street, so vehicles do not attempt to go in the middle, because that's an accident waiting to happen.
Space them 20-40 meters apart and traffic will still be flowing without the constant crashing sound.
(for our street, my guess-timate is 20 meters).
Paint them yellow, or yellow/black stripes. Yes, it's ugly. Ugly is visible.
Have a clear sign indicating the speed limit. One that looks like a speed sign.
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