Research was conducted on the effects of nonmotorized traffic flow on motorized vehicle speeds on the basis of field observations of vehicle speeds on Chinese roads. A linear relationship was observed between motorized vehicle speeds and nonmotorized traffic flow under a range of motorized traffic flow volumes. By using the relationships of non-motorized flow effects obtained in this study, together with free speed and speed-flow relationships investigated in other studies, a general congested speed model for predicting vehicle speeds under various road characteristics and traffic flow volumes has been developed. The generalized speed-flow model can be incorporated into the three-zone speed model used in the Highway Development and Management (HDM-4) model.
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