Stan (Stratejik ulaştırma planlaması modeli)'nin Türkiye demiryolu ağına uygulanışı

Abstract

The network optimization model that is used to simulate network flows in STAN is a nonlinear multimode multiproduct assignment formulation that minimizes the total generalized system cost. The generalized system cost is applied to links and transfers which are identified in the network and has components of train running costs (monetary units per train-km) and train delay costs (monetary units per train-hour). In order to find train delay costs, a volume/delay function that was given in STAN had been used. Delay functions are most important, since they describe analytically the effect of the traffic intensity on the facility by the estimates of the time necessary to pass trough the facility. Consequently, in models for tactic and strategic planning, capacities are generally not considered as explicit and hard constraints but are instead incorporated into volume/delay functions. Delay functions are defined in yards, at transfers and over the links of the network and thus permit an estimation of the total trip time, from the origin of the traffic to its destination given the capacity and the levels of traffic present on the network. In this study volume/delay functions are applied only to links. For each link a volume/delay function is constructed and these volume/delay functions are calibrated for each situation that is considered. The volume/delay functions are not applied to yards because the avarage service time and capacity may be quite difficult to evaluate precisely in most cases. For yards there is no standart way of optaining a reasonably accurate estimate of capacities. Often only historically observed yard put-through values are available. Consequently, when the yard is not a bottleneck in a given network, nor is it expected to become congested in a future scenario, a constant ( estimated from observed values ) delay function may be used for yards. But unfortunately we, in Turkey don't have such observed values so I was not able to put yard delay functions in my study. Another important aspect of any freight transportation system is the presence of a significant traffic of empty vehicles. The impact of empty vehicle movements on both the operations and planning of a transportation system is very important for the rail mode, since rail vehicles are captive to the infastructure and, thus, the empty car movements take place on the same rail lines with the loaded ones. Consequently the train flows and over the link delays are significantly increased and therefore the proper modeling of stategic rail planning must consider the flows of empty cars. The general procedure that is used to model empty car movements in the network is: a) Define the empty car product and its transportation characteristics b) Estimate the origin destination demand matrix for this product c) Include this demand in the general model and treat it as any other product.