Institute for Transportation

About the research

The Transportation Research Board’s (TRB’s) National Cooperative Highway Research Program (NCHRP) Synthesis 439: Use of Transportation Asset Management Principles in State Highway Agencies explores the state of practice for transportation asset management among state departments of transportation.

About the research

The objective of this research was to identify the main reasons for bridge decommissioning in the United States. Relevant studies from the literature reported deficiency, poor National Bridge Inventory (NBI) condition ratings, lower load-carrying capacities, vulnerabilities, and road widening projects as the most common causes of bridge decommissioning. A common finding in earlier studies was that the reasons for decommissioning could not be identified for a significant portion (15% to 30%) of the records.

For the first analysis in this research, decommissioned structures were identified from historic NBI files, and their characteristics were analyzed. Based on a national survey performed for the project, a literature review, and an initial analysis, potential drivers of decommissioning were identified. These potential drivers were then compared with agency reasons gathered from five States (Utah, Michigan, California, Pennsylvania, and Florida). The final task was a comparative analysis of the decommissioned structures with the new structures that replaced them.

Overall, functional improvements are the major driver of bridge decommissioning, and they also explain a majority of unexplained cases. Structures replaced for functional reasons are also replaced younger than the structures replaced due to poor condition on average. Although the potential drivers provide sufficient identifiers of decommissioning, drivers derived from the NBI data by themselves are not specific enough to explain decommissioning as comprehensively as agency-provided reasons.

About the research

The objectives of this research are to (a) quantify the costs and benefits of a formal partnering process and (b) prepare a recommended AASHTO Partnering Handbook, Second Edition.

Visit the AASHTO Partnering Handbook, Second Edition project website at the Transportation Research Board for more information.

About the research

Increased concern for environment and worker safety requires that alternatives be found to avoid working with hazardous materials. An alternative for the calibration method using mercury in Section 4 of AASHTO T 153/ASTM C 204 is needed. The objective of this project was to add an alternative method to AASHTO T 153. The new method must not use hazardous materials and be safer to use than the current method while maintaining the accuracy and precision of the current method.

The researchers concluded that mechanical devices can be use to measure and calibrate Blaine cells with sufficient precision to allow users to conduct measurements without the need to handle mercury, and proposed changes to AASHTO Test Method T 153 to allow use of physical measurements. The report was forwarded to AASHTO staff to make it available to the chair and members of the AASHTO Highway Subcommittee on Materials, and to consider adoption of the recommended changes.

About the research

Bridge construction over deep valleys, water crossings with steep slopes, or environmentally protected regions can offer many challenges. The incremental launching method (ILM) for bridge construction may offer advantages over conventional construction, including creating minimal disturbance to surroundings, providing a more concentrated work area for superstructure assembly, and possibly increased worker safety given the improved erection environment. The ILM involves assembly of the bridge superstructure on one side of an obstacle to be crossed, and then movement (or launching) of the superstructure longitudinally into its final position. Despite potential advantages for certain situations, the use of the ILM for bridge construction has been very limited in the United States. The objective of the work was to provide bridge owners, designers, and contractors with information about the ILM, including applications, limitations and benefits.

To clarify the ILM procedure and the current state of practice, a comprehensive literature search and survey were conducted. Recommendations pertaining to best practices for planning, design, and construction activities, as well as applications and limitations for the ILM are also provided. Case studies are presented, which provide specific ILM bridge project information. The use of the ILM for bridge construction will never be the most efficient way to construct every single bridge. However, it is thought that a wider understanding of the applicability and potential benefits would allow potential owners, designers, and contractors to make well-informed decisions as to its use for their upcoming projects.

View the NCHRP project page for more information