Determination of Observation Weight to Calibrate Freeway Traffic Fundamental Diagram Using Weighted Least Square Method (WLSM)

  • Chunbo Zhang School of Transportation, Southeast University
  • Xiucheng Guo School of Transportation, Southeast University
  • Zhenping Xi School of Transportation, Southeast University
Keywords: fundamental diagram, Weighted Least Square Method, observation weight, speed-density relationship,


Due to unbalanced speed-density observations, the one-regime traffic fundamental diagram and speed-density relationship models using least square method (LSM) cannot reflect actual conditions under congested/jam traffic. In that case, it is inevitable to adopt the weighted least square method (WLSM). This paper used freeway Georgia State Route 400 observation data and proposed 5 weight determination methods except the LSM to analyse 5 wellknown one-regime speed-density models to determine the best calibrating models. The results indicated that different one-regime speed-density models have different best calibrating models, for Greenberg, it was possible to find a specific weight using LSM, which is similar for Underwood and Northwestern Models, but different for that one known as 3PL model. An interesting case is the Newell's Model which fits well with two distinct calibration weights. This paper can make contribution to calibrating a more precise traffic fundamental diagram.

Author Biographies

Chunbo Zhang, School of Transportation, Southeast University
PhD Candidate of Transportation Engineering
Xiucheng Guo, School of Transportation, Southeast University
Professor of Transportation Engineering
Zhenping Xi, School of Transportation, Southeast University
Master of Transportation Planning and Management


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How to Cite
Zhang C, Guo X, Xi Z. Determination of Observation Weight to Calibrate Freeway Traffic Fundamental Diagram Using Weighted Least Square Method (WLSM). PROMET [Internet]. 2017Apr.21 [cited 2019Nov.21];29(2):203-12. Available from: