Eco-driving Model For Bus Considering Holding Strategy

With the increasing energy shortage,energy conservation has become an important issue in the transportation sector.Public transportation priority has been regarded as a strategic choice of transformation of transportation mode,and construction of resource-conserving and environment-friendly society.The study of eco-driving for bus is significant to energy conservation,emission reduction,and public transportation priority.Most existing studies on eco-driving studies are concentrated on light duty vehicle instead of bus.For eco-driving research,to reduce the number of stops at signalized intersection is generally considered as the main target when developing the speed advice.Fuel consumption and emission are used as the evaluation indexes,which may cause sacrificing of vehicle running efficiency.Single speed advice strategy could not solve the problem of the bus stopping at the downstream intersection in some extreme cases.Based on the analysis of the bus operation characteristics,bus stops and signalized intersections are determined as the key nodes when establishing eco-driving model for bus in this thesis.The speed from bus stop to the downstream intersection is considered as the optimization objective to build the eco-driving model for bus considering bus holding strategy.Firstly,several scenarios are analyzed based on the consideration of the signal status at signalized intersection and the running conditions of the downstream vehicle.The upper and lower limits of the time window for the target bus are determined.Then,a two-stage speed advice of the bus at the stop and the segment from bus stop to the downstream intersection is proposed.The methods to calculate passenger boarding/alighting time and the maximum threshold of bus holding time are given.The relationships among acceleration,speed,time,and distance are described in detail.Next,the VSP-based fuel consumption model and the Logit-based valuation model of passenger travel time are proposed to quantify the cost of bus fuel consumption and passenger travel time,respectively.Based on the above theories and methods,the eco-driving model for bus considering holding strategy is developed.The minimization of total cost including passenger travel time cost and bus fuel consumption cost is regarded as the objective in the proposed model.Besides,the constraints of the bus running time,acceleration,speed are considered in the model.The bus holding time and accelerations are the decision variables for the model.The genetic algorithm is developed to solve the model.Finally,7 bus stations and the corresponding downstream intersections of the 15th bus line in Beijing are selected as the case study.With the support of numerous measured data,the optimization results of the proposed model are compared with that in real case.The results indicate that the strategy considering bus holding has a significant effect in reducing the average fuel consumption,which is decreased by over 26%.In addition,the average number of stops and passenger travel time are decreased by 38%and 27%,respectively.The results show that passenger travel efficiency is not sacrificed under the environmental-friendly driving strategy.The sensitivity analyses of three parameters in the model,including the valuation parameter of passenger travel time,the distance between the bus stop and intersection,and the bus maximum speed are conducted.The results prove that the distance between the bus stop and the intersection has significant impact on the optimization results.