Noise
The effects of transport noise are not very well understood. There is no fully satisfactory
measurement of noise and the nuisance it causes. The most common unit -- the dbA -- is a relative
measurement, since according to certain authors, there is a difference of 5 dbA between railway noise and
road noise producing the same nuisance. The duration, frequency and regularity of noise all make
contributions to the noise problem that are difficult to evaluate, and even more difficult to measure in situ.
Neither is the monetary evaluation of these effects is very far advanced. The most common
methods of evaluation are:
• Assessing the effects on the market value of buildings. Unfortunately, these methods tend to
disregard the effects of the noise on premises other than dwellings; they also imply that the
economic agents are fully aware of the effects of noise, which is not entirely true.
• Evaluation of actions which would have to be taken to eliminate or attenuate the noise.
Compared with the "market value" method mentioned above, this approach does, in fact,
incorporate the poorly perceived effects of noise, but setting the standard to be achieved is a
highly uncertain and arbitrary business.
• Evaluating the damage caused by noise and the cost of corrective action. This consists
essentially of damage to health, which is itself difficult to assess.