Study On Transportation Network Equilibrium Problems Considering Stochastic Factors

Traffic network equilibrium theory mainly focuses on traffic assignment problems in urban transportation networks.It is used to obtain the traffic flow pattern in urban transportation networks given the travel demands.These results will provide theoretical basis for traffic planning and assessment.Moreover,it has been applied in the field of urban transportation,such as road design,demand evaluation,congestion pricing,transportation network reliability assessment,traffic management optimization,road congestion identification,tradable credit and so on.With the development of the practice of urban traffic planning and further understanding of traffic network flow,traffic network equilibrium theory has been thriving in the last decades.With the development of these studies,the scientificity of urban transport policy is improved.Moreover,it is of great practical significance on saving transportation infrastructure budget,optimizing the allocation of resources,alleviating congestion and so on.The real transportation network is effected by many factors,such as weather,date and time,road construction,traffic accident and so on.Bad weather,such as wind,rain,snow and fog,has a great impact on the road capacity and efficiency.The traffic demand is different even at the same time on different days.Road construction and traffic accident will lead to a temporary closure of one or more lane of the road,which will make the travelers take more travel time on this road.Besides randomness in the transportation networks,travelers,characters are stochastic as well.In other words,travelers are heterogeneous,for example value of time is different between travelers.It depends on the travelers' growth environment and it may vary due to life experience and conditions.The research on randomness in transportation networks can help us get a better understanding of the ways to control traffic congestion.In this study,we firstly develop a Speed Limit-and Reliability-based User Equilibrium and focus on how link-specific speed limits influence the performance of degradable transport networks,in which the capacity of each link is a degradable random variable.The distribution and cumulative distribution of link travel time have been presented with the effect of speed limits taken into account.The mean and variance of link and route travel time are formulated.Three link states have been classified,and their physical meanings have been discussed.The relationship between critical capacity,critical travel time and critical speed limit has been elaborated.Adopting travel time budget as the principle of travelers' route choice,the Speed Limit-and Reliability-based User Equilibrium is proposed.Through numerical studies,we find that for some networks both the mean and standard deviation of the total travel time could be reduced simultaneously by imposing some speed limits.The speed limit design problem has been studied,and it is found that imposing speed limits cannot always reduce the total travel time budget of a network.Then,we investigate a bottleneck model by taking non-commuters and discrete departure time into consideration.Unlike continuous departure time in the basic bottleneck model,the commuters could only choose the departure time from a predefined discrete departure time set and travelers at every departure time.Commuters would leave home to workplace every morning and rationally choose departure time.Non-commuters choose departure time at random due to various reasons such as emergency and so on.The commuters' departure time choice is assumed to depend on the cost budget which is similar to the travel time budget.The solutions of one special case and the general case are derived.Six possible processes are classified.In the numerical studies,the uniform distribution and the log-normal distribution are examined,respectively.It is found that some of the six processes are vanished due to non-commuters.With more non-commuters,the commuters would like to leave home earlier.At last,we try to explore the relationship between the demand of ridesharing passengers,ridesharing drivers and solo drivers in a ridesharing compensation scheme.It is studied by a stochastic ridesharing equilibrium(SRE),which contains a mode choice model and a route choice model.The mode choice model and the route choice model influence each other.The SRE is expressed as a fixed-point problem mathematically.Then the existence of SRE is proved.It is found that there will be a higher demand of ridesharing passengers for journeys with longer travel time.Moreover,too high and too low ridesharing compensation will lead to a low probability of successfully-matched ridesharing.At last,we study the ridesharing compensation design problem to alleviate the congestion in the transportation network.