SCOPE OF THE SPECIFICATIONS The provisions of these Specifications are intended for the design@ evaluation@ and rehabilitation of both fixed and movable highway bridges. Mechanical@ electrical@ and special vehicular and pedestrian safety aspects of movable bridges@ however@ are not covered. Provisions are not included for bridges used solely for railway@ rail-transit@ or public utilities. For bridges not fully covered herein@ the provisions of these Specifications may by applied@ as augmented with additional design criteria where required. These Specifications are not intended to supplant proper training or the exercise of judgment by the Designer@ and state only the minimum requirements necessary to provide for public safety. The Owner or the Designer may require the sophistication of design or the quality of materials and construction to be higher than the minimum requirements. The concepts of safety through redundancy and ductility and of protection against scour and collision are emphasized. The design provisions of these Specifications employ the Load and Resistance Factor Design (LRFD) methodology. The factors have been developed from the theory of reliability based on current statistical knowledge of loads and structural performance. Methods of analysis other than those included in previous Specifications and the modeling techniques inherent in them are included@ and their use is encouraged. The commentary is not intended to provide a complete historical background concerning the development of these or previous Specifications@ nor is it intended to provide a detailed summary of the studies and research data reviewed in formulating the provisions of the Specifications. However@ references to some of the research data are provided for those who wish to study the background material in depth. The commentary directs attention to other documents that provide suggestions for carrying out the requirements and intent of these Specifications. However@ those documents and this commentary are not intended to be a part of these Specifications. Construction specifications consistent with these design specifications are the AASHTO LRFD Bridge Construction Specifications. Unless otherwise specified@ the Material Specifications referenced herein are the AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing.