Road Engineering Journal
Road Engineering Journal
Copyright © 1997 by TranSafety, Inc.
December 1, 1997
TranSafety, Inc.
(360) 683-6276
Fax: (360) 335-6402
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An Evaluation Process for Gypsum Sight and Sound Screens Could Serve as a Model for Future Evaluations

New products, materials, and techniques are continually developed for the national highway system. Most state highway agencies require an unbiased performance demonstration of these products and technologies; this is cumbersome, costly, and time-intensive. To improve efficiency and reduce the time factor, the Federal Highway Administration (FHWA) and the Civil Engineering Research Foundation (CERF) established the Highway Innovative Technology Evaluation Center (HITEC). HITEC assembles technical evaluation teams consisting of representatives from government, academia, and the private sector to assure that new products and technologies will be impartially reviewed and evaluated. Manufacturers of new products apply to HITEC for a technical evaluation; and, with the assistance of the applicant, the team identifies issues for improvement, use, and acceptance of the product.

The Sight and Sound Screen (SSS) is one example of a product that HITEC has evaluated. Developed by the U.S. Gypsum Company, the SSS "is a post-and-panel wall system designed to act as a sight and sound barrier for highways, as well as a privacy fencing system for residential and commercial property." The SSS's basic element is "a factory-produced polystyrene foam panel laminated with DUROCKTM cement board that is finished with a decorative coating." The screen panels are delivered to the site and installed between steel or prestressed concrete columns.

Louis F. Cohn and Roswell A. Harris reviewed HITEC's evaluation plan for the SSS in "HITEC Evaluation of U.S. Gypsum Sight and Sound Screen" (Transportation Research Record 1559). They concluded that whatever the SSS's eventual use as a noise barrier, the HITEC evaluation would be a significant asset in answering questions, establishing credibility in the market, and assisting state highway agencies that are considering using the SSS. In addition, the criteria developed for evaluating the SSS can also be used to evaluate similar systems.

EVALUATION

The evaluation process for the SSS included two phases. The first phase was a detailed analysis of both historical test data provided by the sponsor (U.S. Gypsum) and new laboratory test data. The second phase involved analyzing data from field testing the SSS in a variety of environments. Several prototype SSS noise walls were installed by or for state highway agencies around the country; the locations were based on funding availability, construction scheduling, and project characteristics. Of particular interest to the evaluation team were the SSS's potential use on bridges and its "aesthetic flexibility" in special situations--such as applying the Olympic symbol to noise walls in the Atlanta area for the 1996 Olympics.

CRITERIA

The HITEC evaluation team identified several significant evaluation criteria related to the SSS's design, construction, maintenance, and performance.

The team felt the evaluation should look at the SSS's installation process, including equipment needs, work space, and methods of lifting and transporting the panel. The evaluation should consider the mechanical connection of panel to post (i.e., "a detail showing how individual panels will be attached to the steel H beams"). The construction costs of the SSS must be determined and compared with other types of noise barriers. Determining repairability in the field would involve evaluating such factors as the ability to patch a damaged panel (including matching the paint after patching) versus having to replace the entire panel. In addition, the barrier must have access points for a variety of purposes, including maintenance and motorist emergencies.

An evaluation of system durability was particularly important. The SSS must weather well in harsh environments. For example, it must resist chlorine and antiskid agents used in some northern states during the winter. In other instances, part of the SSS will be underground, and it must withstand the effects of moisture and microorganisms. Because noise barriers are often placed across natural drainage areas, the SSS must accommodate the water's normal movement and withstand nearly constant exposure to moisture.

Both the panel cap and panel strength should be significant elements in the evaluation. The panel cap must withstand the rigors of weather and exposure to chemical agents used for ice and snow. The panel must be strong enough to withstand its expected loads and incorporate certain safety features.

Sound transmission loss and sound absorption characteristics must "be determined by an independent acoustical testing laboratory using the appropriate ASTM standards."

As noted earlier, aesthetics come into play when the panel is altered to create designs for special purposes. In addition, the SSS should be aesthetically integrated with its immediate environment and the larger community.

FIELD-TEST PROGRAM

Several state highway agencies constructed as many as 10 full-scale SSSs to fully evaluate the system in areas experiencing highway noise problems. These locations included Corning, New York; Atlanta, Georgia; and Los Angeles, California. The sites had varied historical backgrounds and a variety of construction concerns. Some challenges included construction in a stream environment, application to a bridge, salt impact potential, aesthetics, public interest and perception, funding, and seismic design factors. The Ontario Ministry of Transportation in Ontario, Canada also constructed an SSS for field-test purposes. Weather and durability issues were the focus, specifically "freeze-thaw performance, salt resistance, weathering of finish, and impact resistance."

Cohn and Harris were "responsible for coordinating efforts between the sponsor and the state highway agencies and for ensuring that all pertinent data [were] cataloged for each project demonstration." Staff from the state highway agencies and evaluation team members handled long-term oversight of the projects.

CONCLUSIONS

The HITEC program proved "an effective way to introduce innovative new products to the highway marketplace." Instead of the "inaccurate, incomplete, and even misleading information and data" that highway agencies may receive about a new product, the HITEC evaluation system provided a "structured, unbiased" approach. The HITEC evaluation of the U.S. Gypsum Company's Sight and Sound Screen yielded a number of benefits. In addition to answering questions about the product, helping establish market credibility for the product, and assisting state agencies interested in its use, the evaluation process "should serve as a model to other companies who may want to develop and market new noise barrier materials and systems."

Copyright © 1997 by TranSafety, Inc.



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