The Design-Build (DB) model is an interesting and relatively quite recent model for many countries. In some of the more pioneering countries the DB model has been used for over 7-10 years and for some countries it is becoming the preferred model of choice for most medium and large sized projects. In England and Ireland (not in study) DB is the now the traditional process as DBB is not utilized. Even Estonia is now planning to develop and use the DB model in a pilot project. Recently Rijkswaterstaat (The Ministry of Transport, Public Works and Water Management - The Netherlands) has announced in that DB will be about 90% of project delivery models by the year 2007. In Finland DB is the model of choice and savings in the order of 10% has been reported. Most agencies have indicated that the use of Design-Build model will increase. Also, some refer to Design-Build as the Design & Construct method, which is synonymous. In this report the Design-Build terminology will be used throughout the text.
Also, there have been numerous research studies on the topic and these have come to the conclusion that Design-Build is a viable and acceptable model to use for road projects. Design-Build is especially applicable:
• for time critical projects
• usually within allocated budget
• to increase the potential for innovation
• to optimize the constructability
One recommendation in Hughes (2006) indicates that early involvement by the contractor is required in order for the project to be effectively integrated. The objective of Design-Build is to bring the contractor earlier into the process, and the Alliance model brings the contractor into the planning process at the earliest possible stages of any give project. Koppinen & Lahdenpera (2004) show that Design-Build has an "economic efficiency" much greater than the traditional model and also demonstrates the attributes that can make Design-Build even more effective. FHWA & US DOT (2006) summarizes the results of comparing Design-Build to the DBB (traditional) model and high-lights the benefits of the Design-Build as reducing the overall duration of the project and usually having a positive impact on project costs. In addition, the quality is essentially equivalent to DBB and is highly aligned to projects that have more performance specifications. Greater satisfaction is noted by having lower levels of design development before the tendering process. Warne (2005) also concludes that Design-Build is more aligned to reduced time of construction, improved cost control, equal or better quality, and overall client satisfaction. Also, Carpenter e. a. (2003) recognizes that innovative contracting practices encourage innovation, lower construction duration, reduces cost, and have comparable or better quality. However, the DB model should be used correctly and as it was originally intended.
The Design-Build model can also be utilized in the wrong form or abused, and basically any model can fail if the model is not understood and applied correctly. Koppinen & Lahdenpera (2004) and FHWA & US DOT (2006) include many suggestions, considerations, and recommendations for good practices for Design-Build. It is important to note that in order to make the Design-Build model more effective, the design progression should not be advanced too far prior to the tendering phase. This was a significant comment from many countries using the DB method.
Also there have been many cases of Design-Build for small projects and several clients have received significant benefits from these projects. However, there should be lighter restrictions and tendering requirements compared to the normal Design-Build and it is highly recommended to utilize a so-called "light version" for this process. In Finland the client has developed a light version of Design-Build model for projects typically under 2 million Euros. In regular DB projects, there is a "Request for Qualifications" (RFQ) and bidders are subsequently short-listed to 3-6 competitors before a full tender is provided. Many countries have been recently short-listing to 3 tenders for medium and large sized projects in order to reduce the tendering costs and "false offers".
Table 4 lists some of the benefits and disadvantages of the Design-Build model that were obtained mainly from the private meetings and from many published resources. This should not be considered an exhaustive list.