One of the most important stages of road design projects usually carried out at the first phase is the preliminary road routing. The first question arising for the designer regarding a route design is the information about various routes that the road should access to. The purpose of this research is presentation of an economically optimum model for road routing considering access to all the main points of the roads. The major capability of the model is considering areas that the road should not pass through for any reason. 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, in the second model the forbidden areas are modeled in triangular forms and passing through these areas is prevented. A major point of road corridors 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. An important point in the design of road corridors is determination of general route models, the access sequence to the points and know how of accessibility. Routes should be designed with a comprehensive and long term approach so that they create cost effective road networks. 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. In this research the mathematical non-linear programming has been used for modeling.
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