Introduction The main differences between the deterministic macroscopic models are to be found in pressure expressions and representation of various phases observed experimentally. Methods In this paper, using the laws of fluid dynamics and thermodynamics to describe the traffic flow reality, a new expression of pressure is made and a second order model is proposed. Results It represents different traffic flow phases and, thus, conditions for transition between phases become clear. In addition, our approach suggests solutions to a number of problems yet to be resolved. Afterwards, simulations are presented which show some agreement with experimental data. Conclusion Finally, the proposed model highlights different types of possible actions for traffic flow control.