What are the differences between NEPA and 23CFR772?
There is a major difference between NEPA and 23 CFR 772 requirements for determining traffic noise impacts. Under NEPA, a proposed alternative is compared with a baseline (the no-build alternative) to determine whether traffic noise impacts will occur, i.e. the proposed project itself must create the traffic noise impact. However, 23 CFR 772 utilizes the opportunity provided by a proposed project to consider mitigating current as well as future noise problems. Therefore, under 23 CFR 772, if the predicted noise level approaches or exceeds the Noise Abatement Criteria, there is a traffic noise impact regardless of whether or not the proposed project causes it. Even if existing noise levels decrease in the future, e.g. from 72 dB(A) to 69 dB(A), at a Category B site, there is still a traffic noise impact. A noise analysis based on NEPA requirements may also be necessary in the extremely rare instance where the project itself is expected to create a noise impact (e.g., side-slopes are fla
