The full assessment process detailed in NZS 6806 requires significantly more effort than previous assessments using the Transit guidelines. However, for many routine NZTA projects, noise mitigation is not warranted and neither is a full assessment using NZS 6806. To determine where NZS 6806 requires mitigation, the NZTA has adopted a three-tiered approach to noise assessment. For many projects the Tier 1 and 2 assessments can be quickly and simply conducted by NZTA project staff without the need for acoustics specialists. Tier 3 assessments are not required on all projects, but do require the use of acoustics specialists. The appropriate tier of noise assessment varies for each stage of a project depending on the risk associated with the project.

Tier 1 - Noise risk assessment

A Tier 1 assessment provides an indication of the 'noise risk' associated with a project option. The assessment is a simple process that can be completed in a matter of minutes by a non-specialist. It is based solely on the volume of traffic at the opening year and the number of Protected Premises and Facilities (PPFs) within 200 metres of the proposed alignment.

Tier 2 - NZS 6806 screening assessment

NZS 6806 only requires mitigation to be considered in clearly defined circumstances. The purpose of the Tier 2 assessment is to screen out those project options where mitigation is definitely not required. The Tier 2 assessment for each project option should take no more than 5 to 10 minutes to complete by a non-specialist using the screening tool on the Transport Noise website. The assessment is made on the basis of estimated details of the project (AADT, surface, gradient) and the relationship to the nearest PPF.

Tier 3 - NZS 6806 assessment

The purpose of a Tier 3 assessment is to determine the BPO. This requires an acoustics specialist.

Reporting

The NZTA form PSF/13 is to be used to document the Tier 1 assessment as part of the Social Environmental Screen, and the Tier 2 assessment as part of the Social Environmental Assessment.