Roadside Hardware

MassHighway is keenly aware of the effect highway traffic noise can have on those people who live in close proximity to major highways. MassHighway has reMained sensitive to these issues and has tried to address those most critical areas as funding and other transportation priorities allow. In order to address noise issues in a fair an equitable manner, MassHighway's Noise Barrier program is founded on FHWA noise abatement criteria and policies and MassHighway's noise abatement guidelines. There are essentially two programs; Type I and Type II.

The Type I Noise Abatement Program
The Type I program covers noise barrier construction coincidental with construction of major highways on new location, or physical alteration of an existing highway such as substantial realignment or widening to increase the number of through traffic lanes thereby increasing capacity. Such major projects usually require either an Environmental Impact Statement (EIS) or Environmental Impact Report (EIR) to satisfy the National Environmental Policy Act and the Massachusetts Environmental Policy Act. As part of this analysis, the need for a noise barrier is evaluated for each individual highway project. Under the Type I program, if a noise barrier is determined to be reasonable and feasible, it must be constructed as part of the project. As defined this Type I program is not part of this policy.

The Type II Noise Abatement Program
The Type II Program is a voluntary effort by state highway departments to construct noise barriers along existing Interstate roadways where reasonable and feasible and as funding priorities allow. In order to fairly and equitably assess the needs of the program, MassHighway completed a statewide noise attenuation study of all Interstate highways in March 1989, that prioritized locations to be considered for noise barriers. The study determined, through noise monitoring and modeling, those sites that were predicted to exceed 78 decibels during the loudest hour of the day. At each location, the ability to mitigate noise through construction of a barrier was then assessed. Finally, a list of 53 priority sites</a> (18 at 81 decibels, 10 at 80 decibels and 25 at 79 decibels) was established in accordance with MassHighway policy in the areas of the loudest segments of Interstate highway statewide. These priority locations then need to be further analyzed to determine the feasibility and reasonableness of constructing such a barrier. At this juncture the level of noise reduction that can be achieved, the number of residences benefited, environmental considerations such as wetlands, constructability issues and overall cost are examined.

Validity of the Type II Study
MassHighway believes that the Type II Study and corresponding priority list compiled in 1988 is still valid. The reason for this is two fold. First, traffic volume fluctuations across the state tend to occur on a uniform basis. Therefore, any increases in noise levels due to increased traffic tend to occur on a uniform statewide basis and thus the relative position of sites on the priority list are not likely to change significantly. Second, the nature of highway traffic noise is such that it takes a three-decibel increase to be perceptible to the average human ear. In order to increase by 3 decibels the traffic volume must double and maintain the same speed and a constant percentage of heavy trucks. On most of the Commonwealth's Interstates, if one were to double the traffic volume that produces the loudest hour conditions, the roadways would become so congested that the traffic would slow down and actually reduce noise levels. Therefore additional analysis is a redundant effort that would not yield any new information and funds are better spent on appropriate mitigation.

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