Within the Long-Term Pavement Performance (LTPP) program, two sources of data are used to characterize the climatic conditions for each test section. For the majority of the test sections, data for nearby national weather stations are obtained from the National Climatic Data Center (NCDC) and are used to compute estimated data for a virtual test section located at the test section. In addition, onsite instrumentation is used to obtain site-specific climatic data for the test sections included in the Seasonal Monitoring Program and for the Specific Pavement Studies (SPS)–1, –2, and –8 project sites.

This report documents a study undertaken to examine the reliability and accuracy of the LTPP climatic data. The study confirmed that accurate daily, monthly, and yearly estimates of climatic data for a project location can be derived by using the NCDC weather data for several nearby weather stations. The variation in the climatic data also was characterized.