5. Project Evaluation Kenneth A. Small
Transportation policy making often requires evaluating a proposed discrete change, whether it be a physical investment or a new set of operating rules. Some proposals, like the rail tunnel under the English channel, are one-time capital investments with long-lasting effects. Others, like congestion pricing proposed for The Netherlands, require major behavioral and political groundwork. The optimization framework that proves useful in so much transportation analysis is inadequate to evaluate such all-or-nothing decisions. In an optimization model, important aspects of a problem are represented by a few variables which can be chosen to maximize some objective. For example, Robert Strotz shows how highway capacity can be chosen to minimize total travel costs in the presence of traffic congestion. 1 But often the change is too sharp a break from existing practice, or the objectives too numerous, to represent the problem this way. Perhaps a given highway improvement not only expands capacity to handle peak traffic flows but also speeds off- peak travel, reduces accidents, and imposes noise on residential neighborhoods. Perhaps the required capital expenditures occur in a complex time pattern, and the safety effects depend on future but uncertain demographic shifts. One would like a method for analyzing the merits of such a package of changes, and for comparing it to alternative packages. Such a method is called project evaluation . Performed skillfully, it identifies key consequences of a proposed project and provides quantitative information about them in order to guide policy makers. Much of this information may be non-commensurable: ie, the consequences may not all be measured in the same units and hence the analyst may not be able to determine the precise extent to which these effects offset each other. For example, a tax-financed improvement in airway control equipment might improve safety but magnify existing income inequalities. Thus, project evaluation is typically embedded in a larger decision-making process. John Meyer and Mahlon Straszheim argue, in their classic work on transportation planning, that project 1 Robert H. Strotz, "Urban Transportation Parables," in The Public Economy of Urban Communities, ed. by Julius Margolis. Washington, DC: Resources for the Future (1965), 127-169.
Page 4
2 evaluation and pricing should be viewed as parts of a single integrated planning procedure. 2 They suggest a formal procedure which includes choosing among alternate objectives, such as maximizing profits or maximizing use of a facility. The procedure also involves identifying any constraints on optimal pricing, such as whether or not different prices can be charged to different consumers; such constraints are crucial because pricing distinctions can make a major difference in the social benefits achievable from a given facility design (see the chapter on pricing in this volume). This chapter mainly considers one important part of the project-evaluation toolkit, called cost- benefit analysis . 3 I begin by offering a rationale for combining the costs and benefits accruing to various parties into a single measure. I then explain the wide applicability of "willingness to pay" as a unifying principle in measuring costs and benefits. In applying this unifying principle, I address several specific issues that often arise in transportation evaluations: issues in measuring benefits, issues related to the capital intensity and long lifetime of many transportation projects, issues in properly accounting for externalities. I also consider the effects on economic performance of raising taxes to fund projects. The concluding section returns to the place of cost-benefit analysis in overall project evaluation and decision-making
5. Project Evaluation Kenneth A. Small
Transportation policy making often requires evaluating a proposed discrete change, whether it be a physical investment or a new set of operating rules. Some proposals, like the rail tunnel under the English channel, are one-time capital investments with long-lasting effects. Others, like congestion pricing proposed for The Netherlands, require major behavioral and political groundwork. The optimization framework that proves useful in so much transportation analysis is inadequate to evaluate such all-or-nothing decisions. In an optimization model, important aspects of a problem are represented by a few variables which can be chosen to maximize some objective. For example, Robert Strotz shows how highway capacity can be chosen to minimize total travel costs in the presence of traffic congestion. 1 But often the change is too sharp a break from existing practice, or the objectives too numerous, to represent the problem this way. Perhaps a given highway improvement not only expands capacity to handle peak traffic flows but also speeds off- peak travel, reduces accidents, and imposes noise on residential neighborhoods. Perhaps the required capital expenditures occur in a complex time pattern, and the safety effects depend on future but uncertain demographic shifts. One would like a method for analyzing the merits of such a package of changes, and for comparing it to alternative packages. Such a method is called project evaluation . Performed skillfully, it identifies key consequences of a proposed project and provides quantitative information about them in order to guide policy makers. Much of this information may be non-commensurable: ie, the consequences may not all be measured in the same units and hence the analyst may not be able to determine the precise extent to which these effects offset each other. For example, a tax-financed improvement in airway control equipment might improve safety but magnify existing income inequalities. Thus, project evaluation is typically embedded in a larger decision-making process. John Meyer and Mahlon Straszheim argue, in their classic work on transportation planning, that project 1 Robert H. Strotz, "Urban Transportation Parables," in The Public Economy of Urban Communities, ed. by Julius Margolis. Washington, DC: Resources for the Future (1965), 127-169.
Page 4
2 evaluation and pricing should be viewed as parts of a single integrated planning procedure. 2 They suggest a formal procedure which includes choosing among alternate objectives, such as maximizing profits or maximizing use of a facility. The procedure also involves identifying any constraints on optimal pricing, such as whether or not different prices can be charged to different consumers; such constraints are crucial because pricing distinctions can make a major difference in the social benefits achievable from a given facility design (see the chapter on pricing in this volume). This chapter mainly considers one important part of the project-evaluation toolkit, called cost- benefit analysis . 3 I begin by offering a rationale for combining the costs and benefits accruing to various parties into a single measure. I then explain the wide applicability of "willingness to pay" as a unifying principle in measuring costs and benefits. In applying this unifying principle, I address several specific issues that often arise in transportation evaluations: issues in measuring benefits, issues related to the capital intensity and long lifetime of many transportation projects, issues in properly accounting for externalities. I also consider the effects on economic performance of raising taxes to fund projects. The concluding section returns to the place of cost-benefit analysis in overall project evaluation and decision-making
การแปล กรุณารอสักครู่..
