عنوان مقاله [English]
Routes should be designed with a comprehensive and long term approach so that they create cost effective road networks. The accurate location and details of the roads can't be specified all at once in one stage. Thus alignment is specified in various stages, using different-scale aerial maps and photographs. The first step in the design of road corridors is determination of general route model considering the sequence to the access points. The purpose of this research is to present an economically optimum model for this matter. In this paper after describing a short history of the past studies in the field of road routing, the current methods are evaluated and consequently two mathematical models are presented for route location in plain areas. In the first method the harsh and difficult areas are not modeled. A major point of road corridor design is that the road should be so designed that it could not pass through forbidden protected military or environmental fields. The major capability of the second method is predicting these areas in the optimum road corridor. In rolling and level areas, the costs are mostly dependant on the length of the road. All the costs (including construction and operation), are converted to the unit cost of the road length. Due to different conditions in various roads, the total cost factor will change in different areas. In addition to the construction costs, the operation cost in the design period for each of access points is an important factor in the cost function of the road. Therefore, the importance of the points to which we should have access to, is the major factor for the shortness of the path. The operation cost per kilometer of access road for each point is determined by factors like passenger and goods traffic volume. The total cost function in the analysis of this research is equal to construction and utilization costs. Therefore, in an intercity road or railroad network, the minimum construction cost is a form of the network in which in addition to the appropriate connection of the urban areas, natural resources and industrial centers, the length of the roads are optimal.In this research the mathematical non-linear programming has been used for modeling. These methods convert the problem to a mathematical model and then solve them. Converting a problem to a mathematical model increases the ability to investigate it, and therefore, provides better opportunities to get benefit of a variety of mathematical programs.An important application of the presented mathematical models is therefore their utilization in provision of master highway and railroad corridor plans in plain areas. Such corridors may also be used in route location projects in larger scale maps, in plain areas. The presented model in this paper yields the final route corridor in a way that economic, social and political requirements of the project are fulfilled. All the cost parameters of the route length can enter the model. The natural and geographical phenomena like valleys, mountains, lakes, lagoons, soft soils, environmentally protected areas, are able to be included in this model.