Modified two-fluid model of traffic flow

ABSTRACT

Researchers widely use the two-fluid model (TFM) to evaluate the performance of urban networks. However, the TFM is deterministic and does not capture the stochastic relation between speed and density. The present study develops a modified two-fluid model (MTFM). The variance function or the distribution of speed or travel time for a given density is incorporated using a percentile-based indicator, travel time uncertainty (TTU). The percentile-based indicators for the speed distribution are more robust than the variance or other moment-based indicators. The effect of TTU is incorporated using two parameters, $\mathit{\alpha },$ and $\mathit{\beta }$. The applicability of the proposed MTFM is demonstrated using empirical data collected at the corridor and network levels. The TFM and MTFM were calibrated by formulating a nonlinear optimization problem. Based on the investigation using the corridor and network-level data, it was concluded that the MTFM showed better performance than the existing model. .

KEYWORDS:

• Two-fluid model
• travel time uncertainty
• modified two-fluid model

Acknowledgments

The authors would like to thank the Ministry of Housing and Urban Affairs (MoHUA), the Government of India, which financially supported the research project entitled “Development of Framework for Measurement of Sustainability Index for Transportation System in Indian Metropolitan Cities” (File No. K-14011/18/2011-UT-IV (e)). The present study was part of this project. The authors are also thankful to the Institute for Transport Planning and Systems, ETH Zurich, for sharing the Largest multi-city traffic dataset. The data can be accessed from http://utd19.ethz.ch/. The authors are thankful to the transportation-engineering department, IIT Madras, for assisting in collecting traffic data using Wi-Fi sensors. Their support is sincerely acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Ministry of Housing and Urban Affairs [K-14011/18/2011-UT-IV (e)].