公共工程計畫具有工程複雜及政府投資龐大預算等特性，其執行績效將影響政府預算的分配及經濟的成長。傳統上，績效評估理論大多以公共工程執行的效率、效果與品質為評量指標，忽略了公共工程交易失靈所延伸的成本及對整體經濟效益的影響；而交易成本理論從公共工程交易活動途徑分析，將可彌補傳統績效評估理論的不足。本文蒐集國內重大公共工程北二高之執行量化與質化資料進行分析，研究結果發現:公共工程執行的有限理性、環境不確定性及工程特殊性為交易失靈的主要因素，並引伸相關成本的增加；如果公共工程執行正常，總成本即為工程實體成本加上交易成本（即TC = Ce + Ct ，正常型總成本）；如果公共工程執行落後或延期，總成本分析模式將增加實體成本與交易成本，以及新增的機會成本、社會成本及效用成本等（即TC' = Ce + Ct + Ce' + Ct' + Co + Cs + Cu， 失靈型總成本）。

Public construction project has characteristics of complex engineering practice and huge budget amount of government budget, so it will affect the government budget allocation and even economic growth of the nation. Traditionally, the performance evaluation of public construction projects are judged mostly in terms of efficiency, effectiveness and quality as indicators; however, this approach neglects the costs of transaction failure that may result in other costs or have impact on overall economic growth. If the transaction cost theory is incorporated into the process of the public construction, it will make up the lack of attention on transaction failure of performance evaluation. From the qualitative and quantitative research data of No.2 National Highway project, this research found the bounded rationality of human factors, uncertainty of environmental factors, and special characteristics of the project will increase the total cost. In addition, even if the implementation of public construction proceeds normally, the total cost (TC) should equal the actual expense of construction of project involved (Ce) plus the normal transaction cost (Ct). However, if construction is set back by failures or delays, the method for analyzing the total cost should add the increased construction cost (Ce'), the increased transaction cost (Ct'), increased opportunity costs (Co), social costs (Cs), and utility costs (Cu) (that is, TC' = Ce + Ct + Ce' + Ct' + Co + Cs + Cu).