Abstract
This paper details an analysis performed to support a decision made by the New Jersey Department of Transportation (NJDOT) and FHWA to deviate from the current state noise wall policy when designing replacement noise walls on the I-295-I-76-Route 42 Direct Connection project. Existing noise walls in this area were designed in the 1990s under an earlier NJDOT noise wall policy utilizing FHWA STAMINA2.0/OPTIMA. This model underpredicted noise wall effectiveness and required taller noise walls than necessary. As a result, noise levels behind existing noise walls were well below the abatement criterion of 64 dB(A) (Leq) in effect at that time. Several existing noise wall segments require replacement to accommodate proposed roadway widening. As part of this study, replacement noise walls were designed on the basis of current NJDOT noise wall policy utilizing the FHWA Traffic Noise Model Version 2.5. Although replacement noise walls would provide adequate protection [below the current abatement criterion of 66 dB(A) (Leq)], residences would experience a significant increase in noise levels above predicted no-build levels. These agencies decided that replacement noise walls should be designed to approach in-kind effectiveness, so that residences would experience noise levels similar to those predicted under no-build conditions. To achieve these results, proposed noise walls needed to exceed the height and cost restrictions set forth under the current noise wall policy. This paper includes a concise description of methods used to develop and to apply the unique mitigation plan.
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