EVALUATION OF NOISE EMITTED BY SPEED BUMPS ON ROADS

Philippe Dunez, Christine Bugajny, Geoffrey Pot, Pascal Balmefrezol

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Philippe Dunez, Christine Bugajny, Geoffrey Pot, Pascal Balmefrezol. EVALUATION OF NOISE EMITTED BY SPEED BUMPS ON ROADS. Forum Acusticum Euronoise 2025, SEA, Jun 2025, Malaga, Espagne, Spain. hal-05294105

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# EVALUATION OF NOISE EMITTED BY SPEED BUMPS ON ROADS

Philippe Dunez<fnref n="1" />* Christine Bugajny<fnref n="1" /> Geoffrey Pot<fnref n="1" /> Pascal Balmefrezol<fnref n="2" />

## ABSTRACT

Speed bumps are essential for reducing vehicles speed and so improving road safety but they can sometimes cause nuisances for road-side residents. The main objective of this project is to develop a methodology to evaluate noise emitted by vehicles when they drive on speed bumps and a guide for local authorities and managers in handling these devices. Safety and urban planning benefits of speed bumps can be in correlation with best road- sites residents' quality of life. The Cerema study focuses on common types of regulatory speed bumps, including Berlin cushions, raised platforms, and speed humps. The evaluation is based on measurements with controlled vehicles (light vehicles, heavy vehicles, and two-wheelers). Nearly 600 passages were analysed. Currently, there are no specific French regulations about noise emitted by speed bumps. Cerema proposes noise analysis using energetic and event-based indicators. The study results rank speed bumps based on their acoustic impact. The indicator [LAI<sub>max</sub> - LAF<sub>max</sub>] is proposed to quantify impulsive noise impact. In conclusion, this project enhances knowledges on speed bump noise impacts while applying a specific methodology to evaluate noise and in the possible perspective of future regulations for improving urban traffic management.

**Keywords:** speed bump, noise, impulse, methodology, indicator

## 1. INTRODUCTION

Improving the quality of life and road safety are major issues for citizens. Local authorities wish to limit vehicle speeds to 30 km/h to encourage soft modes of transport and reduce environmental pollution. Speed bumps are commonly installed to force drivers to slow down. However, these devices can generate noise and vibration pollution for local residents, particularly when vehicles slow down or accelerate crossing them, or drive over them inappropriately.

The most common speed bumps considered in this project are cushions, raised and trapezoidal platforms and speed bumps. Figure 1 illustrates these different devices.

<figure><img src="image_3.png" /><figcaption>**Figure 1.** Different speed bumps.</figcaption></figure>

A recent judgement by French court condemned a road infrastructure manager for excessive noise pollution caused by a speed bump. This decision highlighted the absence of rules for objectively assessing the acoustic impact of such devices.

In this context, the French ministry of the environment has commissioned Cerema to develop a measurement protocol

<footnote n="1">¹ Cerema Dter Hauts-de-France, 42 bis rue marais-Sequedin- 59482 Haubourdin, France</footnote>

<footnote n="2">² Cerema Dtec TV, 2 rue Antoine Charial 69426 Lyon, France</footnote>

<footnote>*Corresponding author: philippe.dunez@cerema.fr

Copyright: ©2025 First author et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 Unported License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</footnote>
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# FORUM ACUSTICUM
## EURONOISE 2025

and to find suitable indicators. The aim is to develop an acoustic assessment methodology, tested on several types of speed bumps installed in France, and to identify the specific noise of vehicles passing over them. The aim of the study is to provide a rigorous technical framework to help the authorities better understand these issues and anticipate any legal challenges.

## 2. PRESENTATION OF THE ASSESSMENT

First, a bibliographic research was conducted, highlighting the absence of studies on the impulsive nature of the noise of vehicles passing over speed bumps. Cerema proposed an experimental protocol to characterize noise pollution at emission and calculate the usual indicators and define new ones. Cerema based itself on an existing technical references (standards, guides, etc.), which had to be adapted to the urban context of the sites studied. To set up the project, Cerema made sure to study speed bumps that comply with the normative and regulatory references defining the geometric characteristics of speed bumps. The 1994 decree and the French standard NF P98300 relating to the geometric characteristics of speed humps and trapezoidal speed bumps [1,2] as well as the CERTU guides [3,4] regulate the dimensions and construction conditions. These devices must meet strict criteria in order to guarantee their effectiveness while minimizing nuisances. Geometries directly influence the acoustic and vibration impact of the devices and therefore their acceptability by users and local residents. The study conducted by Cerema is carried out on geometrically compliant speed bumps.

From a regulatory point of view, the noise emitted by speed bumps is not strictly regulated. The 1995 Order on noise from road infrastructure [5] proposes the definition of daytime and night-time levels. In order to characterize event-driven noise, Cerema used the NF EN ISO 11819-1 [6] rolling noise measurement standards, which had to be adapted to the urban context, with the source-receiver distance and reflections from the building.

## 3. TEST PROTOCOL

The test campaigns aimed to evaluate the different types of speed bumps present in France with: 3 Berlin cushions, 3 speed humps, 2 platforms and 1 trapezoidal speed bump. The tests consisted of carrying out controlled vehicle passages (2 Light Vehicles, Truck or Heavy Vehicle and Motorcycle) according to different scenarios (see Tab. 1) which variable crossing modes and speeds, i.e. nearly 600 vehicle passages and 10,000 data analysed.

<table><caption>Table 1. Scenarios studied.</caption><thead><tr><th></th><th></th><th>Berlin cushion</th><th>Speed hump</th><th>Trapezoidal & Plateau</th></tr></thead><tbody><tr><td></td><td>LV x2</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><td></td><td>HV</td><td>No</td><td>Yes</td><td>Yes</td></tr><tr><td></td><td>Motorcycle</td><td>No</td><td>Yes</td><td>Yes</td></tr><tr><td rowspan="3">Speed of passage</td><td>50 to 30 km/h</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><td>30 km/h</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><td>40 km/h</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><td rowspan="3">[Image: Car with wheels on the left and right side]</td><td>In the axis</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><td>Right wheels</td><td>Yes</td><td>No</td><td>No</td></tr><tr><td>Left wheels</td><td>Yes</td><td>No</td><td>No</td></tr><tr><td colspan="2">Number of passages per site (5 passages per scenario)</td><td>90</td><td>60</td><td>60</td></tr></tbody></table>

The instrumentation (see Fig 2.) consisted of:

* Determining a variable of the acoustic environment of the site (using a noise source and comparing it with a free-field site as a reference),

* Installing 3 microphones at the speed bump ramp (reference point) and ± 10 m from it (H: 1.50 m and 50 cm from the side of the road),

* Installing an accelerometer at the reference point,

* Installing a speed radar,

* Using an acoustic camera (searching for the source of the noise emitted),

* Installing a traffic camera,

* Putting sonometer class 1 (measurement over 24 hours near the speed bump),

* Weather records.

All data has been synchronized. The test vehicles used were identical for the 9 study sites, in order to guarantee the reproducibility of the tests, namely:

* A Renault Clio IV 1.5 dCi, LV (1071 kg),

* A Scenic II 1.5 dCi, LV (1375 kg),

* A Mercedes Actros 2042 S, HV (20 t),

* A Suzuki VS800 Intruder 2WD (219 kg).

The objective is to be able to acoustically qualify the speed bumps independently of the traffic conditions. Articulated vehicles (with trailer) and vehicles containing a load (e.g. LCVs) were not included at this stage.
<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /><figcaption>**Figure 2.** Example of an instrumented site (Berlin cushion).</figcaption></figure>

The acoustic indicators sought are: LAeq<sub>6-22</sub>, LAeq<sub>22-6</sub>, L<sub>den</sub>, LA<sub>max</sub>, LAFast<sub>max</sub>, LASlow<sub>max</sub>, LAImpulse<sub>max</sub> and ΔLA<sub>max</sub>. The 1/3 octave spectra, vibrations and traffic parameters were also analysed.

## 4. RESULTS

The 24-hour measurements and the associated indicators (LAeq<sub>6-22</sub>, LAeq<sub>22-6</sub> and L<sub>den</sub>) do not highlight any specific noise due to the crossing for local residents. The time evolutions (at the integration time Ti of 1s) do not allow any impulsive noise to be identified when passing the speed bumps. These indicators were calculated but were quickly abandoned in the characterization of the impulsive noise of speed bumps.

Figure 3 illustrates the temporal evolution of the passage of the 2 LV at the reference point for 4 event indicators (LA, LAF, LAS and LAI). The measurements confirm that the response of the LAS<sub>max</sub> indicator is too slow to characterize an intermittent or fluctuating noise such as an impulsive noise, which means that it should not be kept. The analysis of the other indicators continued by focusing mainly on the noisiest scenarios: crossing at 40 km/h (4 wheels on the speed bump for the Berlin cushions). The deceleration or acceleration scenarios were not included in the syntheses, being considered too dispersed and difficult to reproduce.

The ΔLA<sub>max</sub> allow to estimate the impact of the presence of speed bumps (see Fig. 4). They were calculated as the difference between the noise level at the reference point and the maximum noise level at ± 10m from the speed bump (without acceleration or deceleration). The LA<sub>max</sub> emerge well from 10 dB(A) compared to the ambient noise,

guaranteeing the measurement of the noise of the vehicle passing.

<figure><img src="image_7.png" /><figcaption>**Figure 3.** Example of time evolutions of the 4 event indicators of the passage of 2 LV at the reference point.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>**Figure 4.** Example of time evolutions (LA) of the passage of the 2 LV at the 3 microphones.</figcaption></figure>

Table 2 summarizes all the results obtained at the exit ramp and for a regulatory crossing speed of 30 km/h.

The ΔLA<sub>max</sub> are negative for LV and motorcycle, reflecting a decrease of the noise levels when crossing speed bumps, due to the vehicle speed reduction. The phenomenon is reversed for HV which emit more noise when passing speed bumps. These results are of the same order of magnitude as the results found in the literature, in particular the Cerema study report of 2014 [7], the Vademecum of urban road noise of the IBGE of 2005 [8] and the article "Traffic Noise Enhancement due to Speed Bumps" of the University of Colombo of 2011 [9].
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# FORUM ACUSTICUM
## EURONOISE 2025

<table><caption>**Table 2.** Average sound levels in dB(A), obtained per site and grouped by type of speed bump according to the indicators sought and the types of vehicles, crossing speed of 30 km/h.</caption><thead><tr><th>Speed bumps</th><th>Vehicles</th><th>LA<sub>max</sub></th><th>LAF<sub>max</sub></th><th>LAI<sub>max</sub></th><th>ΔLA<sub>max</sub></th></tr></thead><tbody><tr><td rowspan="3">Berlin cushion</td><td>LV x2</td><td>70.3 &lt; 75.9</td><td>71.9 &lt; 78.1</td><td>73.9 &lt; 81.1</td><td>-4.9 &lt; -4.0</td></tr><tr><td>LV x2</td><td>73.1 &lt; 79.4</td><td>74.4 &lt; 83.5</td><td>75.2 &lt; 86.9</td><td>-6.7 &lt; -1.5</td></tr><tr><td>HV</td><td>86.3 &lt; 87.2</td><td>87.7 &lt; 90.2</td><td>88.9 &lt; 91.3</td><td>-0.3 &lt; +0.4</td></tr><tr><td rowspan="2">Platform</td><td>Motorcycle</td><td>84.6 &lt; 87.1</td><td>87.0 &lt; 89.7</td><td>88.3 &lt; 91.4</td><td>-2.7 &lt; -1.8</td></tr><tr><td>LV x2</td><td>76.5 &lt; 78.3</td><td>81.0 &lt; 81.4</td><td>83.8 &lt; 85.6</td><td>-5.7 &lt; -1.4</td></tr><tr><td rowspan="2">Trapezoidal</td><td>HV</td><td>78.4</td><td>81.1</td><td>82.8</td><td>NA</td></tr><tr><td>Motorcycle</td><td>81.2</td><td>83.0</td><td>84.1</td><td>-3.6</td></tr><tr><td rowspan="2">Speed hump</td><td>LV x2</td><td>75.5 &lt; 78.1</td><td>78.3 &lt; 83.4</td><td>80.5 &lt; 88.1</td><td>-3.0 &lt; -1.0</td></tr><tr><td>HV</td><td>82.7 &lt; 84.9</td><td>85.7 &lt; 87.3</td><td>87.7 &lt; 89.7</td><td>+0.2 &lt; +2.8</td></tr></tbody></table>

In the case of crossing at 40 km/h, the conclusions are more heterogeneous.

Cerema has ranked speed bumps from an acoustic point of view for LV (with all precautions related to site constraints, vehicles and measurement), from the noisiest to the least noisy (for the 3 indicators LA, LAF and LAI):

### Speed hump > Platform & trapezoidal > Berlin cushion

The traffic camera readings indicate that the average speed of the flow of LV gives the same information on the aggressive nature of the speed bump. The average measures crossing speed for speed humps are the lowest one, compared to Berlin cushions and platforms. This suggests that the geometry of speed humps is more aggressive for vehicles and that they are likely to generate more noise than other types of speed bumps, at the same speed.

The LA<sub>max</sub>, LAF<sub>max</sub> and LAI<sub>max</sub> indicators, used alone without a reference value, make it difficult to conclude on the specific acoustic impact of crossing a speed bump and to compare different devices. Cerema suggests to use a relative indicator, in order to avoid ambient noise and site conditions. Cerema also highlights the impact of the vehicle on the noise emitted when passing the speed bump, particularly for speeds above 30 km/h. The front wheel deflectors, or even the bumper, are likely to come into contact with the roadway, generating additional noise (figure 5).

Vibration measurements at the speed bumps showed velocity levels of around 30 to 40 mm/s for LV, with extremes of 11 and 97 mm/s (N: 10 to 20 Hz). For HV,

vibration levels range from 180 to 364 mm/s. For each vehicle category, the vibration levels recorded are equivalent on the different speed bumps. The propagation of vibration waves must be studied on a case-by-case basis and depends on the nature of the soil, possible reflections with underground networks and therefore parameters requiring a specific assessment per site.

<figure><img src="image_10.png" /><figcaption>**Figure 5.** Illustration of a front wheel deflector and its contact with the road when exiting a speed bump (second view by acoustic imaging).</figcaption></figure>
<figure><img src="image_11.png" /></figure>

# FORUM ACUSTICUM
## EURONOISE 2025

### 5. APPLICATION OF NEW SPECIFICS INDICATORS

Cerema began by studying the audio signals recorded as vehicles passed over speed bumps. This type of analysis allows for a detailed examination of vehicle passages at the axle, with the possibility to determine the speed of passage and observe significant variations in sound pressure in case of an impulsive event. This type of analysis provides detailed information on passages but is not relevant for assessing the noise disturbance induced by a speed bump. Cerema focused on the indicator using impulsive time weighting ($LAI_{max}$). The $LAI_{max}$ level at time t was compared to the $LAI_{max}$ at time t - 100 ms (see Fig. 3) to quantify the nature of the impulsive noise when a vehicle passed. However, Cerema deemed this indicator difficult to identify on a temporal evolution, not very visual, and difficult for local residents to understand. In addition, it is necessary to perform the measurements with a short integration time (≤ 100 ms).

Figure 3 provides another interesting approach with the difference between the LAI and the LAF at the time of the noise peak when passing over the speed bump, i.e. [$LAI_{max}$-$LAF_{max}$]. The identified advantages are:

* The integration time at 1s is the integration time easily achievable with any class 1 sonometer,

* The data are retained at the instant of $LAI_{max}$, to avoid any misinterpretation with possible shifts due to time weightings,

* The environmental variable, reflecting the site conditions, is not considered in this relative calculation.

Another advantage is the possibility of highlighting the deflector-roadway contacts thanks to the study of this impulse indicator at +10 meters. Figure 6 shows, as an example, all 15 passages of a LV (acceleration upon exiting the speed bump, stable crossing at 30 km/h and 40 km/h) over a trapezoidal speed bump. The indicator makes it possible to identify impulse noise, particularly at the reference point.

The [$LAI_{max}$-$LAF_{max}$] indicator remains below one decibel at -10 meters upstream of the speed bump, showing the absence of impulsive noise. At the reference point, this indicator increases highly, ranging from 2.5 to 4 dB(A), and can exceed 5 dB(A) depending on the passages. The impulsive nature of the noise is demonstrated for this speed bump. Downstream of the speed bump, at +10 meters, the [$LAI_{max}$-$LAF_{max}$] indicator is also very marked depending on the scenario. This impulsive noise at +10 meters is

attributable to the noise of the deflector contacting the roadway (or the bumper) at the exit of the speed bump (see figure 5).

This indicator and this type of representation make it possible to determine if the noise emitted by the speed bump is impulsive or not and if it is significant. These results, measured in the immediate proximity of the speed bumps, do not, however, reveal the potential discomfort felt by local residents. The most acoustically aggressive devices could be identified by the indicator [$LAI_{max}$-$LAF_{max}$]. The analyses confirmed the initial classification of speed bumps based on $\Delta LA_{max}$.

<figure><img src="image_12.png" /><figcaption>**Figure 6.** [$LAI_{max}$ - $LAF_{max}$] of passages of a LV on a trapezoidal speed bump, at different speeds.</figcaption></figure>

The thresholds for this indicator and the number of exceedances remain to be defined and then validated by the relevant authorities before practical application.

### 6. LIMITATIONS OF THE STUDY

In this part, Cerema precise the limitations and choices made for this experimentation.

First, the vehicles selected for controlled crossings do not represent the entire vehicle fleet or vehicles with not well secured loads that could generate additional noise. They were chosen from Cerema's vehicle fleet and guarantee the reproducibility of the tests.

About the location of the measurement points, Cerema opted for three points, adjacent to the speed bump, as well as upstream and downstream. Similarly, while the 50 cm distance from the road does not comply with the regulations for rolling noise measurements (7.5 m), this choice made it possible to characterize the speed bumps regardless of the site configuration.

Regarding the crossing scenarios, and particularly the crossing speeds, Cerema is aware that they are not
<figure><img src="image_13.png" /></figure>

# FORUM ACUSTICUM
EURONOISE 2025

representative of typical road traffic with forced crossing speeds higher than the average traffic speed.
Measurement uncertainties must be considered too.

## 7. PERSPECTIVES

After this experimentation, Cerema has proposed a simplified test protocol incorporating:

* A geometric survey of the speed bump,

* Reproducible speed bump crossing measurements with controlled vehicles,

* Acoustic measurements at the exit of the ramp and at +10 m for microphones located 50 cm from the edge of the road and 1.20 m above the ground,

* LA, LAF, and LAI measurements,

* Knowledge of traffic (flow and speed at the speed bump),

* An analysis of $[LAI_{max} – LAF_{max}]$.

Cerema proposes adding an assessment of noise at the facade of the building affected by the speed bump. It is specified that the objective is not to ensure proper insulation of the façade with interior measurements, but to estimate noise as defined in the regulations relating to noise from road infrastructure and to assess the impact of the speed bump on the observed noise levels.

There are no acoustic regulation for speed bump implantation on roads.

In addition, vibration measurements can be carried out near the speed bump and on the building.

The study will continue in 2025 with an analysis of complaints handled by various infrastructure managers. This capitalization should result in an organizational chart describing the different stages of processing a complaint relating to noise from speed bumps and the various stakeholders: local residents, local authorities, infrastructure managers, and experts.

Cerema specifies that this study will need to be supplemented in the future by a perception assessment of local residents who are disturbed by noise pollution when vehicles are passing speed bumps. This study must be accompanied by measures to define the value of the indicator $[LAI_{max} – LAF_{max}]$ from which the disturbance could be perceived (considering the distance from the building to the speed bump). The number of passages that could cause disturbance could be taken into account via an indicator of the form $NA_{[LAI_{max} – LAF_{max}]}$ as in aeronautics. These thresholds must be discussed with French central administrations with a view to changing the regulations.

## 8. REFERENCES

[1] Decree No. 94-447 of May 27, 1994, relating to the characteristics and conditions of construction of speed humps or trapezoidal type speed bumps, France, 1994.

[2] Standard NF P98-300 Road speed bumps type speed hump or type trapezoidal - Geometric characteristics and construction conditions, France, 1994.

[3] Guideline CERTU, Speed humps and trapezoidal type speed bumps, France, 1994.

[4] Guideline CERTU, Cushion and platform Guideline, France, 2010.

[5] Order of May 5, 1995 relating to noise from road infrastructure, France, 1995.

[6] Standard NF EN 11819-1: Acoustics - Measurement of the influence of road surfaces on noise emitted by traffic - Part 1: statistical method on passage, France/CE, 2023.

[7] B. Soldano, "Noise measurements at the passage, Berlin cushion rue des Vanneaux, Strasbourg", Cerema, 2014.

[8] Vademecum of urban road noise, Local road developments and their influence on road noise, part II: sound influence of vertical drops, IBGE, Belgium, 2005.

[9] S.N. Wewalwala et D.U.J. Sonnadara, "Traffic Noise Enhancement due to Speed bumps", Journal of Physics-University of Colombo, Sri Lanka, 2011.