Research On The Application Of Travel Time Reliability In Transportation Planning

Road network reliability analysis is used to analyze and evaluate the constructed road network.Usually,we need plenty of money to reconstruct existing road network to improve the reliability of existing network.So,if we incorporate reliability analysis as an integral part in the planning of road network,we can save plenty of money.Unfortunately,the traditional transportation planning method is based on the hypothesis that each part of road network operates with its designed capacity,without considering the reliability of road network.Whereas,the concepts and methods to calculate existing indices of road network reliability are studied deeply and systemically.And the travel time reliability is chosen to embed the transportation planning process.So reliability analysis is combined with the transportation planning process.A method of transportation planning which is suitable for both the need of network reliability and future traffic demand.The core of traditional transportation planning process is traffic planning prediction which is composed of four phases,that is,traffic generation prediction,traffic distribution prediction,traffic mode-split prediction and traffic assignment prediction.The appraisal of travel time reliability of road network is done just following traffic assignment and the planning scheme in this paper.Different causes which influence the operation of links and different operating modes of each link are considered.This makes the transportation planning process more practical.An approximate method named CBMM,which is used in communication network at first,is chosen to evalute the travel time reliability of road network in this paper after studying various methods to calculate travel time reliability deeply.Firstly,a series of most probable states of road network is determined.Then,the travel time of each state is calculated under UE and SUE.The level of service of each state is determined. The threshold of travel time reliability is calculated at the end.The influence of different route choice behaviour to travel time reliability is analyzed based on a small network.And the result is satisfactory.