| As the global climate is deteriorating,severe weather events happen more frequently than ever.According to statistics of Ministry of Transport,the economic losses arising from climate change in recent ten years reach to 10 billion.Therefore,the influence of severe weather on traffic is a hot research topic in the traffic field in recent years,and many scholars have begun to pay attention to the change rules of travel behavior and travel demand under severe weather.At the same time,with the development of social economy,cities are becoming more and more connected and the demand for intercity travel demand is growing.Compared to travel in the city,the intercity travel is characterized by long time and long distance and more easily influenced by severe weather.Although the negative effect of severe weather on intercity travel has been confirmed by many scholars,the influence of severe weather on travel behavior and road section traffic flow is mainly analyzed in the existing literature and few scholars pay attention to the effect of severe weather on intercity OD(Origin-Destination)flow.However,the real-time and accurate OD requirements are the foundation of operation management,and it’s necessary to explore the change rule of OD flow of intercity travel under severe weather deeply and systematically to provide the basic support for transportation emergency security under severe weather.Pursuant to Shandong expressway toll station data,global climate data website and weather data of historical weather forecast for China,this paper studied the influence mechanism of severe weather on OD flow of expressway intercity travel.Firstly,the effect of the real-time weather variables at the starting and ending points and the prospective and lag weather variables on the expressway intercity travel volume was analyzed and the influence of various severe weather at the starting and ending points on the expressway intercity travel volume was explored;Secondly,the difference in the effect of various weather on intercity travel OD flow based on different destination areas,different travel distances,travel purposes and vehicle types was analyzed and the influence mechanism of the interaction effect between weather factors and non-weather factors on the expressway travel volume was explored;Thirdly,the spatial correlation of intercity travel volume was analyzed from the perspective of spatial correlation and the spatial spillover effect of local severe weather on travel demand in adjacent areas was explored;Finally,in terms of time and space,the long-term and short-term effects of severe weather and the influence mechanism of direct and indirect spatial effects on intercity travel volume according to these two effects were studied.The specific research contents were as follows:(1)Reveal the influence law of various severe weather on expressway intercity travel volume at the point O and D.Based on the expressway vehicle traffic data at a single OD point,a research framework was proposed to systematically analyze the relationship between three real-time weather variables(basic weather continuous variable,severe weather dummy variable and OD point weather difference variable)and two non-realtime weather variables(severe weather lag variable and severe weather advance variable)as well as the expressway travel volume and the first order residual autoregressive model of the relationship between them was constructed to systematically discuss the influence of five weather variables at O and D points on expressway travel volume.The results showed that,except for the weather at O point,the difference of rainfall and snowfall between OD points had a significant influence on the intercity travel demand,but the difference of temperature,wind speed and visibility between OD points had no significant influence on the travel demand.Moreover,the effect of snowfall and rainstorm on the expressway OD flow had a one-day prospective effect and a two-day lag effect;The weekend and afternoon travel demand was more sensitive to the impact of severe weather.(2)Explore the influence mechanism of interaction effect of weather factors and non-weather factors on the expressway travel volume.On the basis of expressway vehicle traffic data at a single O point and multiple D points,the districts and counties of Shandong Province were divided into six metropolitan areas,the mixture effect negative binomial model between freeway travel volume and independent variables was constructed,and the influence mechanism of the interaction effect of weather factors,travel distance,travel time and vehicle type on the intercity travel volume was analyzed.The results indicated that the influence of weather factors on the intercity travel volume in the same metropolitan area was homogeneous,while the influence of weather factors on the intercity travel volume in case of destination in a different metropolitan area was heterogeneous;As the travel distance increased,the influence of foggy weather and snowy weather gradually increased,but the effect of strong breeze and intense fall gradually decreased;The influence of hot weather and foggy weather on the travel volume on weekends was significantly higher than that on weekdays.Furthermore,the influence of hot weather,strong breeze and intense fall on passenger car flow was greater than that of truck,while the effect of foggy weather and snowy weather on truck flow was greater than that of passenger car.(3)Research the spatial spillover effect of severe weather on expressway travel volume in adjacent districts and counties.Based on the expressway vehicle traffic data at multiple O points and a single D point and the spatial weight matrix under different rules,the spatial lagged model,spatial autocorrelation model and spatial Dubin model for the relationship between weather factors and expressway OD flow were constructed and the influence of severe weather on intercity travel volume in similar districts and counties was explored.The results showed that the spatial Dubin model based on the random effect under the adjacent regular matrix had the highest goodness of fit;The travel volume of the expressway in each district and county was of spatial correlation,and the snowy weather,intense fall and extreme temperature had a significant negative effect on the expressway travel volume in adjacent districts and counties;The influence of snowy weather and foggy weather on the truck travel volume in adjacent districts and counties was greater than that of passenger cars,and the influence of intense fall and extreme temperature on the passenger car travel volume in the nearby districts and counties was greater than that of the truck.(4)Analyze the short-term and long-term effects of severe weather on expressway travel volume in different cities and direct and indirect effects under these two effects.On the basis of vehicle traffic data at multiple O points and different D points,the dynamic spatial lagged model of severe weather and intercity travel volume was constructed.The results indicated that except for cold weather,the short-term effect of all other severe weather on expressway travel volume was lower than the long-term effect.Except for light rain and foggy weather,direct and indirect influence of all other severe weather on the expressway travel volume were of significant negative impact.It’s also found that the light rain and temperature-related weather factors had a positive influence on the travel volume of expressways with tourism city attributes.The research in this paper helps to more deeply understand the relationship between weather and highway travel demand,providing the basic support for transportation emergency security under severe weather.The results can be used for intelligent transportation system and provide a scientific basis for formulating differentiated,accurate and regionally collaborative travel guide and control strategies for different time periods,travel distances and vehicle types. |
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