This paper presents recent developments and applications of three- (3-D) and four-dimensional (4-D) modeling on two transportation projects and their added value for constructability reviews. Transportation projects are characterized by challenges, such as design complexity, right-of-way acquisition, utility relocation, and traffic management, which truly need to be addressed by constructability reviews so as to make projects successful by minimizing delays, cost overruns, change orders, and so on. The 3-D and 4-D computer-aided drafting (CAD) models are new emerging tools that can tremendously aid constructability reviews. Although the models are extensively used in building projects for this purpose, their use in transportation projects is limited. The 3-D and 4-D CAD models in building projects could also be applied to transportation projects. The 3-D and 4-D CAD model applications developed for the two transportation projects in this paper emphasize the value added by this new technology to communication, technical design checking, construction planning, and work area management applied to transportation projects.

Reconstruction of major metropolitan highway projects is a complex engineering process during which detailed engineering plans and specifications are prepared and the construction operations are performed according to those plans and specifications. Most of these complex projects take years to plan and design and several more years to construct. One major challenge associated with urban and metropolitan highway reconstruction is balancing the mobility needs of the driving public and the construction needs of the contractor. In general, this balance is accomplished through the development of detailed traffic control plans (TCPs). These TCPs are primarily engineering documents. Typically, they are shared between an engineer, owner, and contractor on printed sheets of 11- 3 17-in. paper. On large projects, a TCP document can consist of several thousand sheets. A TCP depicts the sequence of construction and the management of traffic (i.e., spatial information only). Timeline information (i.e., temporal data on the construction sequences) is contained in a separate system for scheduling data. Since the turn of this century and through the availability of powerful personal-computer-based, three-dimensional modeling tools, scheduling software, and their integration, the latest visual modeling techniques have become possible and cost-effective to use in the development and presentation of complex spatial and temporal engineering information to project stakeholders in a user-friendly format. This paper presents a case study of the successful use of this technology on the $2.6 billion Lyndon B. Johnson Freeway reconstruction project in Dallas, Texas.

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