Development of Accurate and Reliable Annual Average Daily Traffic Factoring Methods

Details

• Creators:
  Zhao, Li ; Madarshahian, Mahyar ; Sadeghnejad, Amirmohammad ; Huynh, Nathan
• Corporate Creators:
  University of Nebraska--Lincoln. Nebraska Transportation Center
• Corporate Contributors:
  Nebraska. Department of Transportation ; United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  Data Analysis Quality Control Quantitative Metrics Sampling Traffic Surveillance Transportation Planning
• Publication/ Report Number:
  SPR-FY25(048) ; 26-1121-4071-001
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States ; Nebraska
• Edition:
  Final Report: 07/01/2024 - 5/31/2026
• Corporate Publisher:
  Nebraska. Department of Transportation
• Abstract:
  Accurate estimation of Annual Average Daily Traffic (AADT) is essential for the Nebraska Department of Transportation (NDOT)to support planning, design, safety evaluation, asset management, and federal reporting requirements. Because continuous traffic monitoring is not feasible at every roadway location, NDOT relies on short-term traffic counts that are expanded to annual values using temporal adjustment factors (TAFs). The selection of appropriate temporal factors directly affects the reliability of AADT estimates and, consequently, the quality of transportation investment decisions. NDOT's current practice primarily relies on month of-the-year-based adjustment factors, with additional day-of-week considerations. While this approach follows national guidance, the performance of alternative temporal adjustment structures has not been systematically evaluated under Nebraska-specific traffic conditions. Differences in seasonal variation, holiday effects, and roadway functional characteristics may influence the accuracy of various temporal aggregation levels. Therefore, a comprehensive assessment of candidate temporal adjustment factors was necessary to determine the most accurate and reliable approach for estimating AADT from short-term counts in Nebraska. The objective of this project was to evaluate multiple temporal adjustment factor structures and identify the most suitable options for NDOT's roadway functional groups. Eleven temporal adjustment factor structures were evaluated, ranging from monthly to daily and week-based configurations. Performance was assessed using error-based metrics that compare estimated AADT values against ATR-derived annual averages. To support implementation, this project developed an Excel-based tool that incorporates the three recommended temporal adjustment factors. The tool automates data formatting, factor calculation, AADT estimation, and error evaluation. It is designed to be user-friendly and compatible with NDOT's existing workflow, minimizing implementation barriers. The tool allows engineers to select among the recommended factor options depending on data availability and operational needs. The findings of this study provide NDOT with a data-driven basis for improving AADT estimation practices. Adoption of the recommended temporal adjustment factors, particularly in combination with 48-hour short-term counts when feasible, can enhance the reliability of AADT values used in planning, safety analysis, and funding allocation decisions. The accompanying implementation tool further facilitates practical application of the research results.
• Format:
  PDF
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:f8225a93dcf54030b29bbb6bf94744e19b6c215130f736bae76d986d2381d664f2f2925e26566c8d6b83dd3a5a376eba7d1f5f44fc170524d9cfae7b04fa7bb5
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/92840/dot_92840_DS1.pdf
• File Type:
  [PDF - 1.98 MB ]