6. Track environment and maintenance

6.1 Environment

The term environment requires two constraints to be specified:

• influence of the environment on the track, through terrain and climate;

• influence of the track on the environment, through rolling noise.

Climate and the natural environment have a major impact on the track's performance. Atmospheric conditions, particularly precipitation (rain and snow), have a direct impact on ballast. Drainage therefore plays an essential role on the subgrade.

The major environmental impact of railroads is the rolling noise generated by passing trains. This is particularly important in residential areas. The main means of reducing noise on the track...