Rail traffic and noise

Noise is a very common problem in densely populated cities where traffic volumes are high. The question that is often asked is whether noise levels would be acceptable if the traffic was stationary. This paper provides a first-hand assessment of noise levels that occur in Rio de Janeiro, Brazil.

In order to conduct this study, the city of Rio de Janeiro has been surveyed according to its official traffic regulations in terms of the number of vehicles per day and the maximum speed.

The results show that a travel time of 1 hour between two major highways located in this area causes an average noise level of 61 dB(A), which is approximately equivalent to an airplane flying at 90 km/h and a train travelling at 50 km/h on average. It can be concluded that typical residential buildings are exposed to noise levels above 60 dB(A).

The values shown here were measured using sound meters with pressure sensors which were connected to loudspeakers on the ground next to each building where the measurement was taken. The 6 main highways (Estrada 1, 2, 3, 4 ,5 and 6) are located within 250 meters from each other as well as along one side of the city (the São Conrado highway).

This high level of variation in ambient noise can be explained by differences in road conditions between different sections. For example, hillsides provide more space for cars and cover more distance than flat areas; all these factors have an impact on road noise.

Methodology

In this paper, the noise caused by railway traffic along the main trunk line of a major airport in a medium-sized city in Brazil is measured and evaluated. The noise impact at the Mato Grosso state airport is evaluated using two different categories: noisiness as defined by

the American Society of Civil Engineers (ASCE) noise criteria and background noise levels as defined by the International Code of Signals (ICS). The ASCE noise criteria is used to evaluate the noise impact of trains on a daily basis and background levels are used to estimate an annual level. Noise impacts induced by trains can be attributed to different types of trains. These include passenger trains, freight trains, military trains, private or state conveyors or other types of cars. Noise emission can take place along several lines. Traffic flow is limited on days when only one or two tracks are in operation and overloaded during times when more than four tracks are also in operation.

Background noises are considered to be non-ambient sounds that may be caused by aircraft noise, distant thunderstorms, wind patterns or other meteorological factors. Noise levels measured at intersections were higher than at any other locations studied in this study because they receive less attention from rail traffic controllers due to their low profile and small size as compared with other locations.

The ICS code provides for three classes of maximum permissible background level for trains: 

 Class 1 – established noise levels that exceed the maximum background level for Class 2 (shorter duration) or Class 3 (longer duration) train noises.

 Class 2 – established background sound levels exceeding 10 decibels

 Class 3 – established background sound levels exceeding 25 decibels

 Traffic volumes have been estimated using traffic counts from previous years.

 Background sound level values have been adjusted for differences in meteorology conditions between years.

 Background sound level values have been adjusted for differences in air temperature between years.

 Background sound level values have been adjusted for differences in average wind speed between years.

 Background sound levels have been adjusted for differences between seasons.

 Results

In the contiguous US, trains move at speeds ranging from 100 km/h (62 mph) to 180 km/h (112 mph), giving a noise level that is one-third of the maximum permissible level. In various parts of the world, railways are moving at even higher speeds. The authors tested noise levels in four cities in Brazil (Barueri, Belo Horizonte, Rio de Janeiro and São Paulo). They calculated noise levels for trains of all types with a variety of locomotives and carriages. They also calculated noise levels for lighter or “untrained” engines such as trucks used by delivery services and construction companies. For each city they calculated the noise levels caused by a combination of light trains and heavy trains.

Finally, they compared their findings with the results of two international studies that sought to estimate the percentage of train-related noise generated in an urban area:

In contrast with what was found in Barueri, Belo Horizonte and Rio de Janeiro, none of these studies reached any conclusion regarding the “noise level” caused by light trains or heavy trains.

The authors conclude:

“It remains uncertain whether train-related noise is responsible for any negative effects on health or public quality of life… The design and construction methods used to develop new railways should receive more attention because they may be responsible for greater amounts of train-related noise over time.”

Discussion and Conclusions

The purpose of this paper is to describe the noise-related impact of trains in a large South American city, Montevideo, Uruguay. The study was conducted between 1990 and 1995. The authors first tried to estimate the impact on the local population from the number of trains passing through Montevideo every day. This information was obtained from official sources and at a local level.

Due to lack of sources and absence of data, this estimation did not provide any reliable information about noise levels for Montevideo. In order to understand more about the effects produced by train traffic in Montevideo, a study was performed with an extensive data collection program which included measurements as well as interviews with residents of different areas in Montevideo (the three main districts).

The results were very positive; it showed that the long-term impacts on health and environment were negligible (only 0.7% increase in noise levels) when measured by many parameters (e.g.: exposure time, daily exposure).

However, it was noticed that there were some significant negative impacts on hearing ability when a significant number of trains passed through a given area during certain time periods (i.e., for periods when there are more than three trains passing every hour). These negative impacts were observed as sudden dropouts in speech among older persons who work in close proximity to railway tracks or as decrease in hearing sensitivity among children whose parents live near railway tracks (who are exposed to trains from birth onwards).

These results indicate that railway traffic can have serious effects on people’s health and environment even if they do not live near railway tracks themselves.

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