In 2003 ADOT adopted a Quiet Pavements Program to overlay most of the Regional Freeway System with rubberized asphalt to address the annoying noise associated with the ever-increasing level of traffic. The program initiated its first project in the summer of 2003 by overlaying 23 miles of concrete freeway with 78,000 tons of the rubberized asphalt at a cost of $5.5 million.
Similar projects have been completed since then, with the intent to cover the entire Regional Freeway System with the quiet-riding rubberized asphalt surface.
On the current Superstition Freeway widening project, the rubberized asphalt to be placed this spring is a hot mix asphalt (HMA) that contains 9-percent liquid asphalt cement (80-percent is liquid AC and 20-percent is crumb rubber from recycled tires).
The rubberized asphalt overlay used on ADOT projects has reduced noise levels by three to five decibels, with greater noise reductions recorded in some areas.
FNF leads the way
FNF Construction, a leader in the general/heavy highway construction industry, has been a strong proponent in the utilization of asphalt rubber paving in the Southwest. The company has been promoting the smoother, quieter and more durable benefits of rubberized asphalt pavements since the mid-'90s.
Arizona has taken an aggressive approach in specifying and promoting the use of asphalt rubber pavements, and FNF has played an integral role in helping the state achieve its quiet pavement initiative.
The benefits of rubberized asphalt, particularly as a thin open-graded friction course that delivers a smooth, quiet and durable surface, have been validated by ADOT's aggressive usage on many road rehabilitation projects.
With traffic noise becoming more of an issue in densely populated urban areas, delivering a pavement solution that not only addresses the durability and smoothness demands of agency owners, motorists and taxpayers, but also mitigates pavement/tire noise is a bonus.
The FHWA's Noise Abatement Criteria requires noise abatement for residential areas when the traffic noise levels approach or exceed 67 decibels. Transportation agencies commonly build sound barrier walls that cost $1 to $5 million per roadway mile. Rubberized asphalt has proven to be a much more cost-effective alternative in reducing noise levels.
The partnership FNF and ADOT have built in designing quiet pavements will continue to benefit motorists, taxpayers and the environment, as old tires are put to a new use in reducing the noise pollution of urban areas while delivering a safe and smooth ride for motorists.
When the current Superstition Freeway widening project is completed in a few months with the placement of a one-inch thick asphalt rubber open-graded friction course, FNF and ADOT will have added yet another stretch of quiet pavement motorists and adjacent residential neighborhoods appreciate.