It is most interesting that the NRA (National Roads Authority)/ TII (Traffic Infrastructure Ireland) continue use a design goal of Lden=60dB as part of the process to decide if noise mitigation ‘is or is not required’ on new road schemes as part of the Environmental Impact Assessment process, given conflicting views in other research based documents.
When we examine the European Environment Agency’s document titled ‘Good practice guide on noise exposure and potential health effects, EEA Technical report No 11/2010‘, it would appear that there are conflicting views on what might be a healthy exposure level to traffic noise and what is being used by the NRA/TII.
In the EEA Technical Report 11/20110, it sets out endpoints that can be qualified as intermediary effects in relation to noise exposure. These endpoints can be used to assess special situations where the uncertainty in relation to the endpoints in terms of health and well being is large (e.g. noise sources for which exposure‑response relationships have not been established).
If we compare the NRA/TIIs design goal Lden=60dB, it would appear that there is a substantial gap between what has been proposed by the NRA/TII and what the EEA suggests. See Table 2 below extracted from EEA Technical Report 11/20110.
It would appear that the EEA document suggests that and Lden=60dB is at the threshold that gives rise to the effect of ‘Ischaemic heart diseases’. It would appear also that Lden=50dB is at the threshold of hypertension, which is at a level which is some 10dB, Lden lower than the NRA/TII design goal.
It would be our view that it would make sense to apply some of the SFI and EPA research funding to areas like this to determine if the NRA/TII’s design goal of Lden=60dB is appropriate or fit for purpose given the conflict with the EEAs guidance on the known effects of noise on heath and well being.