Optimization model of number of scheduled freight train formation cars
The determination of the number of formation cars is an important part of making a scheduled freight train plan, and it also has a large influence on the benefits of railway freight transportation. First, the influences that affect the number of formation cars are analyzed. Secondly, taking the maximum freight transport benefits as an objective, and comprehensively considering the primary factors that include service frequency of freight trains, section traction weight, effective length of arrival-departure tracks, and so on, this paper establishes the optimization model of the number of scheduled freight train formation cars. Finally, the solving method for the model is presented, and a case is given to show the solution process. It provides a reference for decision-makers of railway freight transportation.
A mathematical model for the fixed-time traffic control problem
Abstract The paper deals with the fixed-time traffic control problem, which consists of finding a periodic schedule for the signals controlling the vehicular traffic in a system of intersections. A traffic model is used which allows for constraints on green durations, conflicts and coordinations. The resulting mathematical model is formulated as an extension of the feasible differential problem of network flow theory over a special graph associated with the intersection system. The fixed-time traffic control problem is proved to be NP-complete in general. A specialized algorithm is proposed for its solution; moreover, an alternative solution method based on mixed-integer linear programming is given. Finally, a real example is modelled and solved.
TRAFFIC SIGNAL CONTROL OF ROUNDABOUTS
Full signal control of traffic was introduced in 1978 at a 35 M diameter, three approach roundabout near the centre of Nottingham. This paper describes the development of the control method giving formulae used to determine cycle times, green times and junction capacities. Details are given of the sequence of traffic movements which allows at least one traffic stream to be entering the roundabout at all times within the cycle. Green periods for each entry slightly overlap allowing simultaneous entry for two streams over short times. Results of "before-and-after" surveys indicate that the entry capacity was increased by 10 to 40 percent according to the time of day, and that the flow could be significantly increased by junction control if it were accompanied by physical changes in layout. Other benefits include reduced delays and better overall control of the junction using urban traffic control systems.