An interview with
Doug Forstie
When did ADOT decide to focus on pavement smoothness and what did you do to achieve this goal?
- Constructing smooth pavements has always been a major goal for ADOT.
- In 1991 we decided to implement a pavement smoothness spec with incentives and disincentives to reward the contractors who construct smooth pavements.
- We started with a few pilot projects and now virtually all paving projects have the incentive/disincentive spec.
- Since implementation began, the average roughness has dropped from 38 inches per mile to 24 inches/mile on our Interstate highways.
What role has the Asphalt-Rubber friction course played in improving our Interstate highways?
- The ARFC is the final surface course placed on virtually all of our Interstate highways.
- The ARFC is easy to place and allows the contractor to construct a very smooth final surface.
Has ADOT conducted any tests to verify the noise reduction of ARFC?
- Limited tests have been done to date.
- ADOT sponsored a research project in 1995 that indicated a noise reduction of 3-5 decibels.
- Public opinion is that rubberized asphalt is quieter.
What is the design life of ARFC?
- It's not yet established, but 10-14 years is certainly possible.
- We have some ARFCs over concrete that are 13 years old and still performing adequately.
- AR-ACFCs are designed to last 7-10 years when used over PCCP pavements.
Arizona has excellent relationships with industry. What has ADOT done to accomplish this and what benefits are seen from developing these good relationships?
- We have committed to being a partner with industry and this partnering effort touches all phases of our business, from design through construction.
- To maintain these relationships, we regularly meet with all industry groups and mutually discuss relevant issues and specification development.
- The major benefits are that ADOT and industry are on the same sheet of music and when problems occur, they can be resolved in an open and honest manner.
Doug Forstie is materials engineer for the Arizona
Department of Transportation and chairman of the task force created
by the American Association of State Highway & Transportation
Officials to explore the need for crumb rubber asphalt mixture
standards. He graduated from Arizona State University in 1969
with a Bachelor's degree in Civil engineering and has been a
professional engineer, working in the highway construction and
materials business for 32 years.
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Letter
to the editor
Paving wisdom
I read the paper every morning and haven't seen any comment on the newest portion of the I-17. I want to congratulate the state for a dramatic improvement. Little noticed is, with the rubberized asphalt paving two things have occurred.
First, the noise generated by all vehicles is at least 50 percent quieter, which most probably made the huge walls lining I-17 unnecessary.
Further, being a NASCAR team owner, I know how important fuel efficiency is. For the novice, next time you drive I-17 notice how smooth the ride is. This means your tires aren't bouncing off the pavement but producing efficient use of power, i.e., increased miles per gallon.
Phoenix is also utilizing the same paving with the same results. A job well done. I for one want to praise the wisdom shown by our governments in Arizona!
Roger LaMoure
Phoenix
less fuel consumption
Westrack study confirms smooth pavements save fuel
In a paper prepared for the International Conference on Accelerated Pavement Testing in Reno, Nevada, Oct. 1999, a noted group of transportation scholars and researchers led by Dr. Jon Epps, University of Nevada, Reno (now professor emeritus) verified smooth pavements equate to fuel savings.
"As the roughness of the pavements increased due to structural damage from traffic loading, there was an opportunity to study vehicle operating costs due to increased roughness. In January/February 1998 after 1.5 years of continuous loading, the track had reached its roughest condition.
The track was so rough that measurements at the driver's location indicated that the driver would not be able to tolerate the ride for more than a few hours. Accordingly, the track was rehabilitated in early March 1998 resulting in a significant reduction of roughness.
This period of time (i.e. prior to and after rehabilitation) provided a unique opportunity to evaluate truck operating costs versus pavement roughness. During this time frame the pre and post rehabilitation IRI were 150+inches/mile and approximately 75 inches/mile, respectively.
During a three month period, 60 days prior to and 60 days after rehabilitation, fuel consumption was measured in two of the trucks. Average fuel consumption before rehabilitation was 4.2 mpg, while afterward it was 4.4 mpg.
This difference amounts to a 4.5 per change. For the average truck, traveling 1,000,000 miles, this translates to a savings of nearly 10,300 gallons as a result of the "smoother" pavement. Obviously this would result in significant costs savings and reduction of emissions to the environment."
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