This study is carried out to examine two public construction projects delivered by traditional approach (Design/Bid/Build) with five issues of (1) formal and informal relationships between key parties involved in detailed design and construction phases; (2) project organization for construction; (3) decision-making process for resolving requests for changes (RFCs) of construction contractors; (4) communication process for reviewing requests for information (RFIs) and submittals of construction contractors; and (5) influences of relationships between key parties on processes of time, cost and quality control during a construction phase. This research includes two main purposes. One of them is to recognize similarities and differences in the five above issues to understand and to learn from this. The other one is to suggest several recommendations to enhance performance of public construction projects that are delivered by traditional method (Design/Bid/Build). To answer the research questions, there are two project-cases formed in the study as foundations for comparison and analysis. One of them is River Nid bridge construction project in Norway and the other one is U Minh bridge construction project in Viet Nam. Furthermore, these two cases were established by using project materials and interviewing with key individuals involved in the projects. Throughout comparison and analysis between the theory and both the Vietnamese and Norwegian cases, and between these two project-cases, this study concluded: In the detailed design phase, that the management of the detailed design and review of the detailed design are conducted by two separate individuals in both the Vietnamese and Norwegian cases makes the degree of the functional relationships in both these two cases more complex than in the theoretical case. However, this can bring significant benefits for the project performance because there are potential chances of achieving a more feasible detailed design. In the construction phase, hiring the supervision consultants (SC) - the third party for supervising the contractors’ construction activities makes the functional relationships in both the Vietnamese and Norwegian cases more complex than in the theoretical case. This can bring both advantages and disadvantages for the project performance. There need to have (1) a suitable control system much focusing on the activities of both the third party and the construction contractors, and (2) a system for resolving conflicts to limit these disadvantages to increase the project performance. The trust and personal relationships can be established before or after the beginning of the project, and bring many benefits for the project performance. However, the trust relationships can have negative influences on the project performance since they cause subjectivity. Good personal relationships, and clear and sufficient contract terms can prevent the negative influences of the personal relations on the project performance. The level of the authority delegation for decision-making for resolving the requests for changes (RFCs) of the construction contractors in both the Norwegian and theoretical cases is deeper than in the Vietnamese case; and the time of the information exchange between the design consultants (DC) and the construction contractors in both the Norwegian and theoretical cases is less than in the Vietnamese case. This may lead a consequence that the project performance in both the Norwegian and theoretical cases are more effective than in the Vietnamese case. The positive attitude of the key parties is a decisive factor to achieve the positive influences of the functional relationships on the processes of the time, cost and quality control during the construction phase. The functional relations’ negative influences made by significant conflicts are more likely to perform in the processes of the cost and quality control than in the process of the time control. The high level of certain trust and good personal relationships can help to prevent the negative influences of the functional relationships. The trust relationships may help to increase the project performance since they result in conflict reduction in the processes of the time, cost and quality control during the construction phase. However, there need the high degree of certain trust relationships to achieve the actual positive relations of the trust relations on the processes of the cost and quality control. This is because these two processes are sensitive, so there need the high degree of certain trust relations to create chances for the less control of the construction activities of the construction contractors. The personal relationships can make the increase of the project performance due to better communication. This benefit is achieved mainly throughout what the personal relationships positively affect the processes of the time and cost control during the construction phase. Meanwhile, the impacts of the personal relationships on the process of the quality control are limited. Throughout the comparison and analysis, especially recognizing interesting points in both the Vietnamese and Norwegian cases, there are nine recommendations suggested to increase the performance of the public construction projects that are delivered by traditional approach (Design/Bid/Build). These recommendations address project owners, project managers and construction managers who are responsible for organizing and managing these public construction projects.