Cover Image

Not for Sale



View/Hide Left Panel
Click for next page ( 15


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 14
14 which also require that "manuals describing the relative Calibration Centers calibration procedure and other aspects of deflection test- ing should be kept in the vehicle and office" (Holzschuher To implement the 1994 calibration procedure, LTPP opened and Lee 2006). Relative calibrations are required either four calibration centers. Currently, those centers are oper- monthly, if the FWD sees regular usage, or within 42 days ated by the DOTs in Colorado, Minnesota, Pennsylvania, of any given data collection operation. Checklists are given and Texas. Additionally, the privately operated Dynatest for before transit, before operations, and after operations calibration center in Florida and JILS calibration center in (Schmalzer 2006). California provide calibration services. These calibration centers have since put the 2007 FHWA calibration process Travel Distances and Costs Associated with into practice. At the Texas calibration center, the TxDOT Calibration method can also be used. On average, the Texas and Penn- sylvania DOT calibration centers see about 30 FWDs per Because relative calibrations can be performed on any sur- year, the Colorado calibration center sees about 20, and the face where pavement layers are adequately strong, travel Minnesota calibration center sees about 8. None of the cali- distances tend to be short. According to survey data, 52% of bration centers charge SHAs for calibration services; how- SHAs travel 0.62 km (1 mi) or less to a relative calibration ever, the Colorado, Pennsylvania, and Texas centers charge site. Additionally, relative calibrations tended to be inex- at least $300 per session to private firms. pensive. The same survey showed that 52% of respondents spend less than $100 per relative calibration (Appendix B, Training requirements differ slightly from one calibra- Question 19). tion center to another. For example, Pennsylvania calibration center technicians are trained by Cornell University and are Reference calibrations, on the other hand, involve signifi- certified by MACTEC. Minnesota, on the other hand, has cant expenditures of travel time and money. Because most not implemented an in-house training program as of the date states require reference calibration once per year at one of of this report, but it plans to do so in the future. the FHWA-certified calibration centers--four LTPP cen- ters, one privately operated by Dynatest, and one privately Sixty-three percent of survey respondents support the operated by JILS--57% of survey respondents reported that construction of additional calibration centers; however, they travel 805 km (500 mi) or further for their reference 76% of survey respondents stated that they are not willing calibrations. Similarly, 64% of survey respondents reported to sponsor such a calibration center (Appendix B, Questions that, including total labor, materials, travel, and other inci- 2021). dental expenses, a single reference calibration costs more than $1,000.