Method and application of grade division for road traffic congestion based on driver's feeling

Although road traffic congestion is an objective state of traffic flow, drivers have different feelings about road traffic congestion. First of all, in order to reveal the law that driver's mental state changes along with congested degree of road traffic, the targeted questionnaire was designed to analyze the driver's psychological feeling under different state of traffic flow. Then, from the perspectives of the driver's subjective feeling, the new definition of road traffic congestion was put forward, so the pressure coefficient of traffic congestion, which is written as chi(t0-tn)(press) is defined to measure traffic congestion pressure. Furthermore, by adopting statistical methods to associate the driver's subjective feeling toward traffic congestion with objective parameters of traffic flow, the grading thresholds of the unblocked state, mild congested state, moderate congested state, and severe congested state were calculated, which are chi(t0-tn)(press) = 0.37, chi(t0-tn)(press) = 0.51, chi(t0-tn)(press) =0.65 respectively. And in the field of application for the grading thresholds, Fourier Transform theory was introduced to calculate domain frequency indexes of the driver's heart rate variability in the four states of traffic flow, respectively. The results show that the domain frequency indexes of the driver's heart rate variability present obvious differences in the four states, which illustrates the solving rationality and applied value of the new grading thresholds for traffic congestion based on driver's feeling. On one hand, the new grading method for traffic congestion, which combines the subjectivity with objectivity, can reflect the driver's actual feeling; on the other hand, it lays the foundation for the study about the influence of traffic congestion on the driver's physiological and psychological characteristics.