The central purpose of this research is to support the Caltrans Quiet Pavement Pilot Program. The research conforms with FHWA guidance provided to State DOTs that conduct tire/pavement noise research. The broader purpose of this research is to support the Caltrans Quieter Pavements Road Map and Work Plan, with goals and objectives that address quiet as well as permeable asphalt surfaces for pavements.
Results from this research will identify best practice for selecting asphaltic surfaces based on performance trends identified from field measurements for noise, permeability, friction and durability. Results will include a literature survey and creation of a database of California materials, designs, and specifications plus similar information from other states and Europe to identify potentially better mixes. Results also will determine whether there is a correlation between laboratory sound absorption as measured by impedance tube and field noise intensity, which could provide a tool for evaluating mixes for noise properties as part of mix design.
Activities within the scope of this research focus on goals and objectives approved by the Caltrans Pavement Standards Team:
* Develop a database for lifetime performance trends to identify best practice for California open-graded and rubberized mixes. * Summarize information on laboratory tests that correlate with pavement performance from the stand point of noise and permeability, and gather information on mix design methods, identifying best practices that can potentially be brought to California. * Survey practice and research in other states and Europe on the lifetime performance of their open-graded mix types with respect to sound intensity, durability, friction, and permeability. Gather and summarize their results, identifying promising mixes. * Determine whether a relationship exists between a laboratory noise absorption test, the impedance tube, and field sound intensity measurements.
Potential future phases of work include conducting new laboratory tests on California mixes and those from other states and Europe for further consideration by Caltrans, and continued long-term monitoring of field sections after the two years approved in this work plan. These future phases will be reviewed by Caltrans at a later date for decisions on whether to proceed.
Deliverables for each research objective are described in the Work Plan. The literature survey by the Partnered Pavement Research Center (PPRC) will include new information from European laboratories and will summarize the state of the art on quiet and permeable pavements. PPRC will become capable of performing tests for much-needed field measurement of sound and surface friction as well as laboratory noise impedance testing. The bulk of project effort will be spent on field data collection that will include eight Caltrans Environmental noise monitoring locations plus approximately 66 mainline highway sites with various open-graded mixes, rubberized mixes, Oregon F mix, and dense-graded asphalt concrete (as a control). These sections will represent different ages, traffic, and climate. Types of data, test methods, and frequency of testing are described in this Work Plan, and PPRC will coordinate with Caltrans Environmental to ensure compatibility of sound intensity data collection. Trend analysis will relate mix performance to variables such as age, traffic, and climate, and will correlate sound measurement techniques.
Project costs and schedule are presented in this Work Plan. The total project cost is approximately $855,000. Nearly 40 percent of this cost is for traffic closures ($324,000) and 20 percent ($174,900) is for equipment. A key risk in this cost estimate is that PPRC does not have funds for required traffic closures and for some equipment.
The project schedule spans a maximum of two years, with data collection after the second year needing to be addressed in a follow-on project. Decision points are included in the schedule so Caltrans annually can decide, after reviewing each year's data, if further testing is warranted. The data collection schedule heavily depends on traffic closures, and might double if District Maintenance crews are unable to support this research effort or funds are not available for contracted traffic closures. The selection of pavement sections with open-graded and rubberized (RAC-G) surfacings also needs to be developed in cooperation with Caltrans Maintenance, who will provide lists of potential sites. Collecting data for DGAC sections is dependent on the PPE2 contractor (Stantec) schedule, so delays in their progress and contract might affect this project schedule. Delays in having the PPRC contract amendment in place by 1 July 2005 also will delay this project.