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Diagram of the NOISE PROCESS
Steps for conducting noise analysis, including the Idaho Transportation Department’s noise policy

Open PDF to see detailed view of the noise process diagram

Icon PDF Noise process.jpg
If a project is likely to increase sound levels (e.g., new road, adding travel lanes, substantially modifying a roadway), then a noise analysis is conducted. The steps are as follows: 

Step 1: Identify areas sensitive to traffic noise (e.g., residences, parks, churches, schools)

Step 2: Determine existing and future noise levels using Traffic Noise Model (software developed by Federal Highway Administration)

Step 3: Determine traffic noise impact (present when noise levels are high enough to interfere with normal conversation OR future noise levels substantially exceed existing noise level) 
- If noise impacts are identified, continue on to Step 4 
- If no noise impacts are identified, no noise abatement is needed

Step 4: Evaluate noise abatement measures using Traffic Noise Model (e.g., noise barrier)


We are here 

Step 5: Determine if noise abatement measures are feasible and reasonable (Based on ability to create appreciable reduction in noise, as well as viability and cost)


If noise abatement measures are determined as feasible and reasonable based on Steps 4 and 5, then the process continues to Step 6. If not, then no noise abatement is needed.


Step 6: Determine preference of adjacent property owners through noise balloting, which takes place during funded design projects 

ITD Noise Policy 

For a noise wall to be approved, ITD policy states that more than 50 percent of affected property owners must vote “yes.” If the property owner vote is 50 percent or fewer, then affected residents are invited to vote. Resident votes must be greater than 75 percent to overturn the owners’ “no” vote.

If noise abatement measures are determined to be desired through balloting, they will be installed with funded construction projects.
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