Federally required state department of transportation (DOT) Transportation Asset Management Plans (TAMPs) must include a process for risk management analysis. State DOTs are tasked with selecting bridges for preservation (including retrofit), repair, and replacement. These needs are seldom met with available budgets. Investment strategies result from evaluating various levels of funding to achieve targets for condition and performance effectiveness at a minimum practicable cost while managing risks. Risks include those that affect condition and performance; environmental demands, such as extreme weather events; and seismic activity.

Unplanned postings and closings related to condition may result from different causes, including originally undetected deterioration affecting strength or stability, substantial change in condition since the previous inspection due to accelerated deterioration, damage from normal traffic or environmental loading on compromised members, and so forth. These situations may be more prevalent in certain bridge types and materials (e.g., timber), component or element types (e.g., truss), element defect types (e.g., corrosion), site locations (e.g., waterway), and so forth. Unplanned postings and closings are distinguished from planned because the former affects bridges that are not currently posted or restricted from carrying legal loads. Unplanned postings may also exclude bridges that are systematically posted to extend service life, not due to the exceedance of safe load capacity.

To provide for meaningful comparison of bridges, the estimated annual probabilities must vary as a function of bridge condition and explanatory attributes. Key explanatory attributes are to be identified. Example attributes may include bridge type and material, elements type and material, element defect type and quantities, load rating values compared to legal load, bridge location and environment (e.g., natural and human), traffic magnitude, age, bridge size and span lengths, presence of deck joints/span continuity, or routine maintenance intensity. The data source used by state DOTs to apply the identified probability values will be readily available or acquired from system-level data [e.g., national bridge inventory (NBI) and state DOT element data].

The objective is to quantify the likelihood of unplanned bridge posting and closing as a function of bridge condition and defining attributes to facilitate describing bridge management risks from condition. The research will quantify at the bridge level in terms of annual probability values that can be applied to individual bridges.

Potential research tasks include:

·       Survey and collect data and information on unplanned bridge postings, including posting load and percent reduction below legal load. Sample a cross-section of state DOTs.

·       Survey and collect data and information on unplanned bridge closings and the magnitude of closings, including partial- and full-lane closure. Sample a cross-section of state DOTs.

·       Analyze data and information and identify the estimated annual probability of unplanned posting as a function of bridge-level conditions and attributes. Determine whether probabilities can be grouped by the percentage reductions below legal load thresholds.

·       Analyze data and information and identify the estimated annual probability of unplanned closure as a function of bridge-level conditions and attributes. Determine whether probabilities can be grouped by partial- and full-lane closure.