基于动态风险饱和度的高速公路交通安全分析

为了反映高速公路运营安全状况，提出了动态风险饱和度理论，构建了动态风险饱和度模型和计算方法。依据路段不同交通饱和度下车辆的驾驶行为，以路段交通安全为约束，研究了跟车行驶和换道行驶2种驾驶状态下，考虑车速变化及雾天等特殊天气条件影响的路段平均最小安全车头时距计算方法，利用建立的安全车头时距与安全流量之间的转换关系，得到不同驾驶状态下的路段安全流量。在不同车辆驾驶状态切换阈值下，计算路段实际交通流量与路段安全流量的比值得到高速公路路段动态风险饱和度值。以G3高速公路某改扩建路段所在路网为例进行验证，计算得到了路网中各路段不同切换阈值下的动态风险饱和度值。动态风险饱和度随着交通饱和度的增大，呈现稳定的先增大后减小的规律，且在换道行驶状态时达到最大，在跟车行驶状态时开始下降，与现有交通安全状态分析相吻合。相较于交通饱和度，动态风险饱和度更能够反应出高速公路路段交通安全动态变化的规律。 

An Analysis of Highway-traffic Safety Based on Dynamic Risk Saturation

The study proposes a dynamic risk saturation theory and constructs a dynamic risk saturation model and a calculation method to reflect the safety operation status of highways. On the basis of the driving behavior of vehicles under different traffic saturation of the road section and the constraint of keeping the road section traffic safety, the calculation method of the average minimum safe headway of the road section takes into account the influence of vehicle speed changes and special weather conditions, such as vehicle speed and foggy in the two driving states of car-following and lane-changing. The established conversion relationship between safe headway and safe flow, is used to obtain the safe flow of road sections under different driving conditions. Under the switching thresholds of different driving states, the ratio of the actual traffic flow to the safe flow of the road section is calculated to obtain the dynamic risk saturation values for road sections. Taking a road network of a reconstructed and expanded section of the G3 expressway as a case study, the study calculates the dynamic risk saturation values of each section in the road network under different switching thresholds. It can be concluded that with the traffic saturation increases, the dynamic risk saturation shows a steady pattern of first increasing and then decreasing. It reaches the maximum in lane-changing driving state and starts to decrease in the following driving state, which is consistent with the existing analysis of traffic safety states. Compared with the factor of traffic saturation, dynamic risk saturation can better indicate the pattern of dynamic changes in traffic safety of highway sections.