They can also be used to obtain advances of work from specialists appointed either by the contractor or by the client (e.g. B under a construction management contract), either for private finance initiative (PFI) or public-private partnership (PPP) projects to obtain contributions from contractors for a consortium applying for a project. The involvement of the contractor in the pre-construction phase is valuable and often essential for the final design process of a project as well as for the preparation of the construction phase, such as the program, cost plans, constructability and any technical purchase. It is important for the client to ensure that they have average insurance means to obtain an alternative offer in the event of failure of the negotiations of the second phase, although this will likely lead to delays and difficulties in design responsibility. However, longer familiarity with the project improves relationships and reduces learning curves and program performance, so that tender prices for two-tier contracts may be higher initially than for single-tier tenders subject to full competition, but the final account tends to contain fewer variations and fewer duties. Competition can be introduced into the second phase through an open book approach when tendering for subcontracting. .