Current State Highway Agencies’ (SHA) Pavement Management Systems are primarily based on surface condition data, and surface cracking is mainly used as an indicator of the pavement structural condition. However, with effective pavement preservation activities that intervene early to preserve and extend the life of pavements and increasingly thicker long-life pavements, the surface cracks can no longer be relied on as a reliable indicator of structural condition or “health” of the pavement structure. This is because most preservation treatments correct surface cracks but do not correct bottom-up fatigue cracking, instead concealing them, while the bottom-initiated cracks continue to develop. In addition, the prevalence of top-down cracking in thicker pavements also makes it difficult to distinguish them from bottom-up fatigue cracking, which is the common indicator of structural deterioration. The true pavement structural condition and rate of deterioration are needed not only to plan optimal structural rehabilitation activities and future budget needs but also for assessing meaningful progress under a performance based Federal-Aid program. With an aging pavement network on our most trafficked highways, the fear is not when the next preservation treatment is needed but when that will no longer be effective, resulting in the need for major rehabilitation / reconstruction. The SHAs state-of-the-practice pavement condition data collection is inadequate to meet this increasingly critical need and some SHAs have investigated the network level use of the Falling Weight Deflectometer (FWD). While FWDs are the preferred device for project level structural evaluation, they are inefficient at the network level. FWD measurements are made at discrete points along the pavement sections and the equipment should remain stationary on the road during each testing point (typically 1-4 minutes, depending on the protocol). Since the equipment has to be stationary during measurements, this requires traffic control and lane closures that disrupt traffic. This limits the productivity and the number of discrete points where measurements can be obtained.
High speed continuous deflection devices were developed as a practical alternative to the FWD for network level pavement structural evaluation. A number of recent studies have investigated the state-of-the-technology and use of high speed continuous deflection devices (1, 2, 3). A more recent effort under SHRP2-R06(F) project titled “Assessment of Continuous Pavement Deflection Measuring Technologies” reviewed all such devices under Phase I of two phase effort and concluded that, for network level applications, there are two potential devices currently on the market – the Traffic Speed Deflectometer (TSD) and the Rolling Wheel Deflectometer (RWD) (1). TSD is manufactured in Denmark and to date is being used in Denmark, UK, Poland and Italy. In addition, several thousand miles of major roads in Australia were tested in 2010 and South Africa has recently purchased a device. The manufacturers of TSD have reported of their plans to make available their latest version of TSD for demonstration testing in the US at their own transportation expense in 2013. Federal Highway Administration’s has initiated a new research project to assess, field evaluate and validate on instrumented and other test pavement sections the capability of RWD and TSD for pavement structural evaluation at the network level for use in pavement management application and decision making (4). Following the field evaluation, validation and identification of technically capable device(s), the research project will also develop analysis methodologies for enabling the use of information obtained from those technically capable device(s) in pavement management.
The objective of the proposed pooled-fund project is to assess the feasibility of and demonstrate the use of Traffic Speed Deflectometer (TSD) for network level pavement structural evaluation for use in the participating state agencies’ pavement management application and decision making. FHWA research project under Contract Number DTFH61-12-C-00031 will compliment this proposed pooled fund study.
Scope of Work
This project will include the following tasks:
1. Coordination and collection of TSD data on agency designated pavement sections for one day of testing at traffic speed, including calibration. Testing length of 30 – 50 miles.
2. Post-processing of all collected data. The agency will be provided with all collected raw and process data in an Excel workbook. Please see comments section for the type of data collected with TSD.
3. Exploratory analysis in the use of pavement structural condition information derived from TSD for use in the participating SHA’s pavement management system and applications.
Minimum commitment per state is $20,000.
The minimum commitment covers first day of testing (including transportation, calibration, 30 – 50 miles of data collection and post processing of data) and travel costs for one representative of the participating agency, or their representative, to attend face-to-face TAC meetings. Factoring in mobilization and calibration time, it is expected that first day testing will provide 30 – 50 miles of data collection. Additional days of testing can be arranged at additional commitments of $5,000/day (maximum daily production is approximately 300 miles).
The specifications of the TSD to be available are described in the documents section.
A waiver has been requested for 100% SP&R Approval
1. Strategic Highway Research Program (2012) “Assessment of Continuous Pavement Deflection Measuring Technologies,” Final Report, Project SHRP2–R06(F), Washington, DC.
2. Rada, G. R. and Nazarian, S. (2011) “The State-of-the-Technology of Moving Pavement Deflection Testing,” Final Report, FHWA-DTFH61-08-D-00025, U.S. Department of Transportation, Washington, DC.
3. Jitin, A., Tandon V., and Nazarian S. (2006), “Continuous Deflection Testing of Highways at Traffic Speeds,” Research Report No. FHWA/TX-06/0-4380-1, Center for Transportation Infrastructure Systems, The University of Texas at El Paso, El Paso, TX.
4. FHWA Contract Number DTFH61-12-C-00031. Refer to Statement of Work in the documents section.