عنوان مقاله [English]
Investment and construction of transportation infrastructures are some of the most complex issues that confront governmental authorities. Uncertainty in the benefits of such infrastructures and, also, difficulty in scaling costs to financial profits, create doubts in the decision making process. Congestion pollution, noise and other issues have significant costs and, therefore, the initial cost of the infrastructure cannot be a proper comparison factor for its economical study. Therefore, it seems necessary to analyze the demand in the horizon year, considering the current situation and using the outcome of planning studies. Evaluating construction and operation costs next to the project profits then leads to applicable decisions. The research aims to study the solution in a particular route case; Sadr expressway in Tehran, which is the sole arterial road to connect the north and north-east of Tehran City to its central region. Studies in the horizon year show that there will be a 104 percent increase of total delay on this expressway in a no action scenario.Pollution and congestion are studied as direct costs of the project, and three alternatives, i.e. maintaining current conditions, a grade separated route (tunnel, in this case) and a metro line along Sadr expressway, are considered as direct cost mitigation solutions for this expressway. The results suggest that direct costs, due to congestion and pollution, are so significant that the profits of the metro line in the horizon year made 17\% of the total cost. However, considering discount rates, profits for the tunnel alternative is only 9\% of the whole cost. In addition, it is concluded that decisions made on just capital costs (without counting for profits) may not be evaluated properly. The metro alternative, though having higher capital cost in comparison to the tunnel alternative, looks more economical in the long term, due to its quicker investment return time. Moreover, it was shown that, in some cases, choosing the no action alternative can be even better than constructing an infrastructure. The pollution cost in the tunnel alternative was estimated as being more than the no action alternative, due to the induced traffic when constructing a new infrastructure.