“…Since it is important to accurately describe the functional relationship among traffic flow parameters, many FD models have been proposed, such as single-regime models (e.g., by Greenshields et al [ 4 ], Underwood [ 5 ], Gazis et al [ 6 ], Drake et al [ 7 ], Franklin [ 8 ], and Newell [ 9 ]), multi-regime models (e.g., by Daganzo [ 10 ] and Smulders [ 11 ]), and stochastic models considering the heterogeneity of drivers (e.g., Jabari et al [ 12 ], Bai et al [ 13 ], and Würth et al [ 14 ]). Recently, Bramich et al ( 15 ) also proposed a general framework for modeling any observed flow–density–speed relationship.…”