Research On Emergency Events Impact Propagation Law In Expressway Network

Acknowledgement of incident impact spreading law in expressway network is the premise of evaluating its robust,and also the basis of formulating rescue plan in emergency response.Though researches in foreign and domestic have obtained significant results,some critical issues remained unsolved,and some results were also inapplicable in domestic transportation environment.With comprehensive analysis in traffic flow theory,this thesis investigates the incident impact spreading law in both basic road section and node area.The model of forecasting incident impact spreading law in expressway network is built,which provides some basis in studying transport network emergency dispatch and evacuation rescue technology.The indicator system leading to traffic condition variation in expressway network under emergency is constructed.With analysis of expressway incident definition and character,remaining capacity is selected to represent accident severity.Main factors affecting traffic variation in expressway network are selected.It is discovered that traffic in transit is the intrinsic driving force,and on-ramp is the carrier when impact spread into the whole network.The Logistic velocity-density model with five parameters which are applicable in emergency condition is built.According to the shortage of unclear parameters meaning in Logistic velocity-density model,parameters are demarcated with field traffic data and LWR basement.The Logistic velocity-density model is constructed,including free flow speed,turning density,bumper-to-bumper speed,heavy vehicle mixing ratio and congested density.Parking wave speed and queue length is estimated in different lane close and v/c conditions,and impact of lane close on incident impact spreading speed and travel time delay is obtained.It shows that the five-parameter Logistic velocity-density model built in this thesis could properly solve the problem of quantifying the impact of heavy vehicle mixing on traffic flow.Aiming at the shortage of current interchange capacity could not accurately describe the node area traffic character under emergency,the concept of Highway Node Acceptance Capacity(HNAC)is provided.Based on Newell’s car-following model,combining driver lane-changing model and traffic simulation,the incident impact overflow condition from road section to network is obtained,and network impact spreading forecasting method based on HNAC is developed.The study shows,HNAC has strong relationships to main road traffic and heavy vehicle mixing ratio.When the mixing ratio remains the same,HNAC is positive correlated to traffic volume.When the traffic volume remains the same and smaller than 10500)3)/3)? 7),HNAC is positive correlated to it.When in the opposite side,HNAC is negative correlated to traffic volume.Besides,when merging volume exceeds certain HNAC,the incident impact will overflow from road section to network.The emergency impact dissipative model in manual-intervention condition is built.The effects of reversible lane,opening emergency lane,and heavy vehicle restriction measures on traffic flow are analyzed using simulation results.The implementation effects of abovementioned measures are verified in aspects of dissipation time efficiency and travel time efficiency.It shows that,though manual control measures have little enhancement on incident impact dissipation,it could significantly shorten the average travel time in evacuation.Moreover,in these three measures,reversible lane processes the best evacuation performance,and its length should be controlled in 6km.