You know that high-pitched whine you often hear on sections of highway pavement? Turns out that it’s as much a safety concern as other traffic issues. For years the Federal Highway Administration has been focusing not only on safe roads but also on quieter ones — from land use planning and control to wall barriers to the surface of the roadways themselves.
According to Robert J. Bernhard, professor of aerospace and mechanical engineering and vice president for research at the University of Notre Dame, “like a long journey, research and innovation at the most fundamental level take time to refine before they can be fully implemented and begin affecting daily life.” As one of the nation’s leading experts on noise control with a focus on tire and traffic noise, Bernhard is finally seeing his work on Next Generation Concrete Surfaces (NGCS) being adopted across the country. Most recently, the Texas Department of Transportation approved the construction of 2 million sq. yds. of NGCS texture for its highways. This makes a total of 13 states — including Virginia, California, Minnesota, Oregon, Kansas and Wisconsin — that have implemented projects or test sections of NGCS since its development in 2007.
Noise pollution is a significant issue affecting more than 18 million people in the United States, especially in urban areas and along highways. In fact, up to 90 percent of the noise generated by passenger cars is a result of tire-pavement interaction.
How much noise is too much? The National Institute for Occupational Safety and Health suggests that the answer depends on the situation and the intensity of the sound and exposure time. For example, a person can engage in normal conversation — typically 60 decibels (dB) — for as long as he or she wants and face no adverse consequences. Typical traffic noises along the roadside range from 70 to 80 dB, but an ambulance siren registers around 120 dB. While it is unlikely that one-time exposure to loud noises would pose an immediate risk of permanent hearing loss unless the sound level equaled or exceeded 140 dB [such as a firecracker], repeated exposure adds up and hearing damage can result over time.
In addition to hearing loss, noise pollution can affect blood pressure, disrupt speech and sleep, increase stress and reduce productivity. Bernhard’s work on NGCS tackled these issues directly by working to change the roadway surface without compromising its performance, durability or safety.
Historically, grooved pavements have been implemented to reduce hydroplaning in wet weather. However, the traditional method of grooving, which involved pulling a rake across the concrete when it was wet (called transverse tining), also created significant tire/pavement noise. For some applications diamond grinding was used to create a smoother surface with fins, which created a positive and irregularly textured surface. This surface was often quieter than transversely tined concrete but not consistently. What Bernhard and his team found is that creating longitudinal grooves [versus transverse grooves] using a “negative” diamond-grinding process allowed for a smooth microtexture and more controlled — and downward — grooves, which is the most important factor in reducing noise levels. Further studies with the pavement grinding industry showed the same results found in the lab could be accomplished in the field with conventional equipment. The resulting NGCS was 1 to 4 dB quieter than other concrete pavements that were created using conventional diamond grinding and 6 to 10 dB quieter than transversely tined surfaces. It also offered improved traction and a smoother, more uniform ride. Equally as important from a maintenance standpoint, studies found NGCS does not change within the first 10 years of construction (it maintains its noise limiting qualities) and is easily renewable.
“It has been a long time coming and success has been very dependent on the hard work of many, many people who know how to build safe and durable highways,” says Bernhard, “but I’m very pleased that these research findings are continuing to progress toward making highways both safe and quieter.”
Along with his work on NGCS, Bernhard has been a frequent consultant to industry and government. His research has been funded by more than a dozen corporations, as well as NASA, the U.S. Department of Transportation, the Indiana Department of Transportation, the Federal Aviation Administration, the Federal Highway Administration and the National Science Foundation.
Originally published by at conductorshare.nd.edu on February 17, 2016.