Improvement Of Transportation Capacity Utilization On Single Track Mixed Traffic Railway Lines

Capacity evaluation is an important subject in every railway system because the capacity of a railway system is not only influenced by the available infrastructure but also,to a large extent,on how the infrastructure is used.Capacity evaluation therefore provides valuable information on how the available infrastructure can be best utilized.It also gives a clear picture of where investments can be made,if need be,to improve the capacity of the network,in cases where the current available capacity is used up.Most railway networks in the world are already approaching maximum capacity utilization in the face of rapidly increasing demand and the railway managers have to find efficient and economic ways to increase the capacity.This study aims to evaluate and improve the capacity of a sing track railway line on which different train types are operated.Railway capacity has been discovered to be very dynamic since it is affected by many factors including infrastructural and operational factors.Also its definition varies depending on the point of view from which it is being defined.The basic definition of railway capacity is that it is the number of trains that can run on a specified infrastructure within a specified time period while maintaining a specified level of service.It has also been established that simply measuring the capacity of a railway line by the number of trains running on it will not give an accurate picture of its capacity especially when the line accommodates different types of trains and is a single track line,where trains running in different directions use the same tracks and cannot cross each other in the segment,they can only cross at the stations.Also noting that for different train types running on a railway line,the sequence in which the trains run has an effect the line capacity.Therefore a more practical way of evaluating the capacity of such a railway line is to measure it in relation to the time it takes for all the trains in a given set of trains arranged in a particular sequence to run on the line.This measure is called the occupation time of the sequence of trains.The time it takes for a train to run on a line is related to the speed of the train,therefore if the speed at which trains run on the line is maximized,the time it takes for it to run on the line will be minimized.The speed of a train can be calculated by dividing the length of the segment by the time it takes the train to run on the line.This means speed is inversely proportional to travel time meaning a minimization of total travel time will result in a maximization of speed which will in turn result in maximization of capacity utilization.Based on this understanding,the capacity evaluation problem was formulated as a mixed integer programming problem with the objective of minimizing the total occupation time of a given set of trains.The model is designed to produce an optimized train timetable with minimal occupation time.This model was applied on the Abuja-Kaduna Line in Nigeria.The current service of the line which runs four passenger trains in each direction in one day was considered as the base case.To test the model,three scenarios were tested;in the first scenario,one freight train was added to the existing four passenger trains,making five trains in each direction.In the second scenario,8 passenger trains and 2 freight trains,10 trains in total in either direction with trains stopping at alternate stations.In the third scenario,twelve passenger trains and three freight trains were run in each direction making fifteen trains in each direction.It was found from the results that applying the model produced optimal train schedules with minimized total running time or the capacity occupation of the set of trains.It also showed clearly the level of capacity utilization of the line.It was also observed that the model was able to produce optimal timetables in a short time for a small number of trains but took a long time to get the results as the number of trains increase.It can therefore be concluded that the model has yielded the desired results,by giving the capacity occupation of a set of trains,the optimal sequence of the trains in the set and an optimal timetable for the train set.This thesis was supported by National key research and development plan of China under the grant fund(2016YFE0201700).