Reducing noise for quieter cities: the Decibel approach from Keolis

What is noise pollution?

Noise pollution refers to all unwanted sounds affecting users, residents, and the urban environment. It originates from transport (road, rail, air), industrial activities, construction sites, and urban life (restaurants, bars, neighborhoods).

Beyond causing auditory discomfort, noise pollution affects public health. Numerous scientific studies highlight the harmful effects of noise on physical and mental health. Prolonged exposure to high noise levels can lead to sleep disorders, increase cardiovascular disease risk, and cause mood disorders like anxiety and depression.

In addition to direct health effects, noise pollution exacerbates social inequalities. Vulnerable populations, often living in poorly insulated housing near noisy infrastructure, are most exposed, reinforcing their vulnerability and limiting access to healthy living conditions. Noise affects not only human health but also disrupts ecosystems, impacting wildlife and animal communication.

In public transport, noise pollution can come from various sources: the screeching of tram wheels on turns, bus engine noise, vibrations from railway infrastructure, or even repetitive announcements.

Decibel: an innovative response to noise pollution in public transport

Decibel relies on a rigorous methodology, structured in multiple stages, to effectively diagnose and address noise pollution. The first phase is based on in-depth diagnostics, combining quantitative and qualitative approaches to identify, measure, and analyze noise sources.

Different methods are used based on territory specifics and identified issues. Acoustic measurements and computer modeling quantify noise levels, map the most impacted areas, and predict the noise impact of new projects or optimizations of existing solutions.

This work is complemented by analyzing complaints and surveys conducted with users and residents, integrating an essential human dimension for a comprehensive evaluation of nuisances. This mix of technical data and local perception guides corrective actions with increased precision.

This structured diagnosis is the first step in the Decibel system, forming the foundation for implementing solutions tailored to residents' expectations and territory specifics.

In Bordeaux (France), confronted with the Mobility Authority's expectations regarding noise management linked to public transport, Keolis Bordeaux Métropole conducted a comprehensive noise diagnosis of its network. This process followed four key stages to assess the noise impact of transport infrastructure on communities and propose tailored solutions.

1. Data collection and analysis included network line paths, operating hours, rolling stock types, speeds, and user complaint history, allowing precise risk area mapping and understanding maintenance activities' impact on ambient noise.

2. Precise measurements were taken on buses and trams along lines and corridors to adjust modeling data to real-world conditions.

3. Maintenance effects on infrastructure were evaluated.

4. Teams modeled noise maps based on collected data.

A summary report provided recommendations for better future noise management. This comprehensive diagnosis shows the importance of a structured, methodical approach to identifying noise sources and proposing effective solutions tailored to local network specifics.

Keolis offers a wide range of options for reducing transport-related noise either at the source or limiting its spread. Depending on context and identified issues, possibilities include:

- Technical solutions like rail grinding and milling (effective on heavily worn rail sections), rail and wheel lubrication (recommended on tight tram network curves), noise barriers in sensitive areas near transport infrastructures, or road improvements (such as using road surfaces designed to absorb vibrations and noise emitted by buses or trams).

- Operational process adaptations like speed reduction in sensitive areas, stop and parking management, vehicle preventive maintenance.

- Adjusting transport offerings: reducing tram speed or rerouting to avoid sensitive areas.

In Nottingham, rail grinding and milling smoothed rolling surfaces, improving wheel-rail contact. The result was a significant reduction in noise emissions, particularly in sensitive areas where noise disturbances greatly affected residents.

With Decibel, Keolis goes further by engaging citizens about noise nuisances. The goal isn't just to reduce transport-related noise but to help residents understand issues and actions taken. This involves consultation devices, awareness campaigns, and information efforts to foster a better understanding of noise nuisances and adopted solutions.

Active listening to citizens and educational responses to complaints help address concerns transparently and inform diagnostics to design solutions truly adapted to field realities.

In London, a specific platform to report noise nuisances linked to the public transport network was established to better meet residents' expectations. This complaint centralization platform not only facilitates noise nuisances' reporting but also addresses acoustic requirements' non-compliance in the real estate sector. It streamlines complaint management and ensures new constructions meet sound standards.

Keolis not only complies with regulations but anticipates residents’ expectations with Decibel. By reducing noise, the company improves urban quality of life. Combining technical innovations and citizen participation, Keolis lays the groundwork for mobility more respectful of its environment.