Apache Technology for Road Conditions: Less Noise, More Sound

With the advent of electric vehicles, one might think that the noise pollution generated by automobiles is about to be resolved. However, 80% of the noise of a car is generated by its contact with the road, the degraded state of a road exponentially increases this noise pollution inside and outside the vehicle. It is with this in mind that Thomas Antoine, Expert Leader in Noise & Vibration Technology at Renault Group, developed the Apache program which consists of mapping the state of roads to indicate the places where a repair would do most good. In terms of noise pollution of course, but also in terms of economy and public health. Thomas Antoine and Fadila Hrird, a Master's student in geomatics applied to urban studies and risks at CY Cergy Paris Université, explain to us how this technology works, their working methodology and describe the many expected benefits.

For Thomas Antoine, the observation is clear: noise pollution is a major societal and environmental problem that he has decided to combat through his work and expertise. The figures speak for themselves: according to the World Health Organisation, 20 million Europeans complain about noise and 8 million sleep poorly. While Ademe, the Agency for Ecological Transition, points out the social cost of road noise in France, estimated at 80 billion euros per year in 2021.

To combat noise pollution on board vehicles (particularly road and air noise), car manufacturers are increasingly using a technology that is very widespread in audio headphones: active sound control. This active control is activated by sound sensors placed around the vehicle that listen to the road and sense the variations in noise it causes. When the noise increases, the sensors inject a sounds wave into the passenger compartment that will sooth the sound spectrum in the vehicle to cancel out the noise heard by passengers and make the journey on board much more pleasant. A manufacturer such as Renault Group could stop there, but the culture of innovation that it holds dear pushes its engineers to go further.

The Apache program, or how to map road conditions

It was while studying active control sensors that Thomas Antoine wondered if it would not be possible to use the signals they generate differently. This is how the idea of the Apache program was born. Apache is a box that analyses the road, like the needle of a vinyl player, and makes it possible to establish maps of the acoustic state of the road network. This data is then compiled to give a very precise analysis of the places where a road is particularly degraded, and therefore noisy. "It is a technology that not only improved the acoustics inside our vehicles, but also allows communities to make more accurate decisions for their road repair budget. So in fact, everyone wins." explains Thomas Antoine.

To create more comprehensive maps, Thomas called on Fadila Hrird. Fadila uses a specific program to create maps with layers of various information such as proximity to senstitive locations (schools, hospitals, retirement homes, etc.) to determin the level of impact that a road can have on local residents.
"We get a huge amount of data from these sensors, but then we need to turn it into useful information. For these maps to be correlated with road usage, we need traffic, and that's where our partnership with Bruitparif comes in handy." - Fadila Hrird.

Partnership with BruitParif, the key to offering a complete service
From the very beginning of the project, Thomas Antoine understood that this detailed analysis of the state of the roads could be of great help to cities and communities for whom the repair strategy is a major issue and a significant part of their budget. This will allow them to very precisely target the sections of roads to be repaired. But for this analysis to be complete, one essential element was missing: their traffic. This data is crucial because it makes it possible to determine the speed at which a road deteriorates and to what extent it generates noise pollution.

This is how Thomas Antoine contacted BruitParif, the Noise Observatory for the Île de France region, which was looking to obtain more information on the acoustic state of the roads. BruitParif quickly joined the project by providing the necessary data and facilitating a test program in the Saint-Quentin en Yvelines area. It was a success and the program has now been extended to the entire Île de France region with around thirty vehicles equipped with the Apache box on the region's roads. The project has now received expressions of interest from several cities in France and abroad. The Apache program is an innovation patented by Renault Group and awarded a Golden Decibel by the National Noise Council, an award that had not been given to a car manufacturer since Renault's Vel Satis in 2001.

Link between noise and energy consumption, the essential data
Thomas and Fadila's in-depth analyses confirmed that a direct link between noise and CO₂ emissions or the range of electric vehicles did indeed exist. The Apache program can precisely quantify the costs and environmental savings related to road resurfacing, and even in how many days the cost of the resurfacting work is offset by a drop in emissions. BruitParif calculated that 1 Euro invested in the road represented 17 to 20 Euros saved on the social cost of noise. To give a concrete example, the resurfacing of the Paris ring road, the busiest road in Europe, would divide the noise level by four and would become a "white" carbon operation after 3.5 years due to an annual gain of 16,000t in CO₂. For Thomas Antoine, this project is a source of pride and a real shift in business. By taking an interest in non-traditional areas of the automotive industry, it is possible to create new value chains for Renault Group. As for Fadila Hrird, who represents a new generation of engineers who have understood that technology can concretely solve problems related to the environment, she is now impatiently awaiting new applications of artificial intelligence to process an ever-increasing quantity of data that will give projects such as Apache ever more relevance.