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72 Chapter 7. Conclusions This research effort examined different aspects of CTD issues, from traditional DBB projects, to urban projects and projects using APDMs, to the incorporation of risk management and post-construction feedback and evaluation in the CTD process. Throughout the research process, the research team was able to reach several conclusions, which are next addressed. One significant finding of this research project is the need to distinguish PDE from CTD. This differentiation is not available in current DOT CTD manuals. Although PDE is a process of apply scheduling methods to come up with a rational estimate of project duration by considering project characteristics and technical information, the estimated project duration is not equivalent to contract time. External factors can dictate the contract time of the project and may require the adjustment of the estimated project duration to comply with the constraints. PDE and those external constraints become the two primary components of CTD. A systematic CTD process is expected to consider both PDE and completion date constraints and compare between the two to establish a reasonable and reliable contract time. A step-by-step procedure for typical highway projects was proposed and included in the guidebook. Urban transportation infrastructure improvement projects often cause inconveniences to the general public. Acceleration of the project schedule is often required to reduce those inconveniences. Most DOT interviewees were aware of the difference and consequences of CTD for urban projects under acceleration compared with DBB projects. However, very few agencies have adopted a systematic approach to determine realistic contract times for urban projects with incentive provisions. An eight-step systematic procedure was proposed in the guidebook to address the unique characteristics of urban accelerated projects. Work packaging is the key to quicker delivery of APDM projects. By breaking down a project into multiple work packages, a work package can begin construction as soon as the packageâs design plans are released for construction, without having to wait until the overall design is 100 percent complete. When it comes to CTD for APDM projects, the consensus from state DOTs interviewed is that only a high-level schedule is sufficient due to limited project information. Effort should be spent on identifying major work items rather than listing every single activity. Furthermore, a CPM scheduling software should be used so that work packaging and the connection between preconstruction and construction activities can be accurately modeled and represented. With the use of CPM scheduling software, time crash analysis can be performed easily by iteratively incorporating different acceleration strategies should the default estimated completion date not meet the external constraints. That being said, professional experience and engineering judgment cannot be understated in determining the soundness of the proposed schedule and subsequent contract time. Although many agencies have developed extensive risk management manuals for project budget and schedule, the review of DOT practices and the interview results with DOTs show that
73 CTD and risk guides remain separate documents. Detailed guidance was proposed and included in the guidebook to incorporate risk management in the CTD process and to help DOTs identify constraints as early as possible and take informed actions to minimize potential scheduling risks. The guide tailored the specific risk management methods to schedule risk analysis. In addition, the effects of the project phase and project size on schedule risk management were explained, and the risk management process was integrated with scheduling methods. Compared to CTD, there is significantly less guidance and procedures on the post- construction evaluation of contract time. Although most DOTs interviewed recognize PCR meetings as a primary mechanism to collect LLs, they do not have any formalized post- construction feedback protocol. Furthermore, several DOTs do not have any database that will facilitate learning between projects. Based on the literature review, the research team has proposed a post-construction contract time feedback loop in the guidebook that demonstrates how the flow of various information generated in each project phase can be collected and taken advantage of for CTD of a future project. The research team also developed a procedure detailing the different steps involved, from proper collection to efficient dissemination of LLs.
