Taming the bridge inventory

May 21, 2010

Highway bridge assets represent a significant national investment. Indeed, there are more than 600,000 bridges nationwide as recorded in the National Bridge Inventory (NBI), with many owner-stakeholders: states, counties, cities, towns and the federal government.

Highway bridge assets represent a significant national investment. Indeed, there are more than 600,000 bridges nationwide as recorded in the National Bridge Inventory (NBI), with many owner-stakeholders: states, counties, cities, towns and the federal government.

Today, there is little question that numerous challenges face the nation as it seeks to address its bridge infrastructure. Over the past several decades, rising traffic demand and heavier loads have taken their toll. Moreover, the bridge population continues to age and deteriorate, with fully one-quarter of the bridges categorized as deficient: either structurally deficient or functionally obsolete.

What is more, bridge owners are experiencing reduced transportation revenue streams as well as diminished buying power, as construction cost increases have outpaced ordinary inflation. Governments also are faced with balancing competing cross-asset funding demands, such as those for education, law enforcement, health care, as well as infrastructure. Because of limited funding for infrastructure, bridge maintenance and preservation have often been deferred and a “worst-first” approach of addressing only the neediest of bridges taken.

In light of the challenges facing the country today, there is renewed national interest with how bridge maintenance and preservation programs, as an integral part of any transportation asset management solution, can be best positioned and administered to meet these challenges. Thus was born NCHRP U.S. Domestic Scan 07-05: Best Practices in Bridge Management Decision-Making.

On approach
The goal of Domestic Scan 07-05 was to review and report on the practices among U.S. transportation departments for the identification, prioritization and execution of programs for maintenance of highway bridges. To carry out this task, an eight-member scan team was formed. The team consisted of individuals from the American Association of State Highway & Transportation Officials (AASHTO), the Federal Highway Administration (FHWA), academia and a private consulting firm. Focus was placed on systematic decision processes and approaches for bridge maintenance and preservation. The scan team was particularly interested in learning how states are prioritizing their maintenance needs and assigning responsibilities for bridge asset management.

Positive input
The scan included a review of documents (DOT manuals, guidelines and policy statements), the collection of responses to amplifying questions from DOTs and travel to sites for meetings with DOT staff. The states visited during the scan included: California, Delaware, Florida, Michigan, Ohio, Virginia and Washington.

Scan travel was completed in June 2009. All told, combining the information acquired via the various means noted above, inputs were obtained from nearly 50% of U.S. states.

Each state has something positive to contribute to the overall process of bridge management. However, no one agency has all of the answers. Because of this lack of a single best-practice example, information has been combined and synthesized in an effort to facilitate the sharing of best practices. This article provides a brief summary of findings and recommendations based on effective practices in maintenance and preservation of highway bridges.

The scan’s key findings are divided into three main categories: the bridge management process, preventive maintenance and agency support. The first of these categories, the bridge management process, further touches upon four elements of an effective process: identification of maintenance needs, performance measures, prioritization and verification. Each of these is further described below, followed by the scan’s key recommendations.

Bridge management process
Bridge management is a process that combines information on needs at bridges, significance of bridge conditions and risks, appropriate remedies and actions, available means of execution and efficient programming and coordination of necessary work. It addresses both bridge network performance levels as well as the occurrence of deficiencies on a bridge-by-bridge basis within the same network. The process must respond to limitations in available resources and derive work programs for specified budget periods. The findings of the scan on the bridge management process touch upon four points: maintenance needs, performance measures, prioritization and verification.

Maintenance needs: The identification of bridge maintenance needs must be uniform, specific and repeatable. This is accomplished through needs identification at the bridge element level. These needs must be stated as standard work actions, so that procedures, expected costs and requirements in permitting and scheduling can be identified. The work needs at bridges should be stored in a corporate electronic database accessible to program managers.

Performance measures: Performance measures are a means of expressing how a bridge owner and its bridge assets measure up to a standard. Measures provide an impetus for gathering and analyzing information about the condition of the bridge inventory. They can drive the tracking of maintenance actions and accomplishments and the effectiveness of maintenance efforts. Performance measures ultimately can help establish and support the need for dedicated government funding for bridge maintenance and preservation activities.

Performance measures also must be matched to objectives in bridge maintenance. Measures must both identify work needed to advance maintenance objectives and provide simple indications of bridge network status. Some states have developed a bridge-preservation allocation formula with rules to replace those bridges that rate less than an NBI 4 (poor condition), to rehabilitate the structures that rate 4 or 5 (fair to poor condition) and to use preventive maintenance on those bridges that rate above 5 (fair to good condition).

States have developed and use many other performance indicators. Examples include the count of bridges with backlogged maintenance work; the count of structurally deficient and functionally obsolete bridges; the network average bridge health index (BHI) (average of total quantities of elements); the count of bridges with BHI < 80; and level of service (LOS) for bridges computed as crew work that is backlogged divided by the full work list for the crew.

Prioritization: Prioritization of maintenance projects should integrate agency objectives for deficient bridges and preventive maintenance on good bridges. The process for prioritization must recognize the effect that deferred maintenance will have on individual bridges and on the network of bridges.

An automated evaluation of priorities would include a multiobject approach that combines the benefits of least cost, risk reduction and preventive maintenance.

Inputs to automated evaluations should include bridge conditions, bridge vulnerabilities (such as seismic and scour), indicators for program managers’ needs (such as paint-health index) and attributes of the bridge inventory.

Procedures for prioritization must engage both central and regional DOT offices and must advance from network-level rankings of candidates to bridge-by-bridge project selection. On the subject of the bridge-by-bridge selection, the involvement of inspectors, maintenance crews and district engineers is paramount. They are very familiar with the local bridge inventory; their knowledge validates both the priorities list and the network plan.

Bridge conditions, for example, can be categorized as poor, fair or good and correspondingly color-coded as red, yellow or green. This rating method can be somewhat subjective, since the states’ definitions of a good bridge can vary. Within this accepted color-coded approach, taking care of yellow bridges on the cusp of becoming red bridges reduces the number of bridges that will eventually fall into the red, thus averting the need for more costly replacements. A holistic approach to prioritization would also include spending great efforts to keep green bridges green. Through preventive maintenance activities, bridge owners can maximize the number of green bridges and reduce the need to do more costly repairs and rehabilitation. Bridge owners must consciously and consistently work to keep good bridges in good condition, rather than be in a continual juggling act with the bad.

Verification: The bridge-management process must incorporate reports of completed maintenance work and the verification, at completion, that the bridge conditions are improved and the risk is reduced or that preventive maintenance needs have been satisfied. Verification often requires integration of DOT data systems. The bridge-management applications used by crews, program managers and planners need to remain current, and the inventory condition must reflect all actions and repairs.

Preventive maintenance
Bridge preventive maintenance has been defined as cost-effective maintenance actions that extend the useful life of a structure. Scan states had differing views of what qualified as preventive maintenance. Activities included such things as routine cleaning, joint repairs, deck treatments, deck replacements, bridge painting, retrofits and other cyclic actions. These activities are performed by most states on some level. To be most effective, preventive-maintenance actions need to occur while a bridge is in relatively good condition.

This proactive approach to preventive maintenance prolongs the life of a structure. Experience in scan states has shown that a preventive-maintenance approach is cheaper in the long run (even if performed frequently) than a major bridge rehabilitation or replacement approach that both is costly and disrupts mobility.

A significant portion of bridge resources (funds, personnel and effort) can be directed to preventive maintenance. Preventive maintenance can succeed in maintaining good bridge conditions, and the actions must be applied before bridge conditions become poor.

DOTs must be able to recognize current needs for preventive-maintenance actions, anticipate near-term needs and follow work programming procedures that deliver preventive-maintenance actions promptly. To recognize and program preventive maintenance, DOTs require trained staff, adequate funding, flexible fund allocations and clear plans of action for bridge components. These last two aspects—allocations and plans—are key. As already noted, funding should be directed to preventive maintenance before bridges become deficient.

DOT staff should recognize maintenance needs related to time in service and not only to the defects extant. These actions preserve the condition, improve the safety and maintain the operation of all bridges.

Agency support
DOT formal organization must support the bridge-management process at all levels. DOT bridge-inspection teams, by training and experience, must be able to identify work needs and to recommend actions. Bridge owners need to leverage the bridge-site inspections for both the identification of needed work and the verification of completed work (from previous recommendations).

Maintenance crews must take initiative in the execution of maintenance work and be guided, but not controlled, by lists of needs from bridge inspections. District maintenance engineers must collect information from inspectors and from crews, evaluate the continuing needs and trends in their bridges and make appropriate applications to DOT central office for funds and for projects.

The central DOT office must operate with quantitative performance measures that are compatible with district operations and must recognize the first-hand knowledge that resides in the districts. DOT executives and government executives generally must accept that maintenance is not an episodic response to deficient bridges, but rather a continuing program of support for good bridges.

Things to do
The key recommendations of the scan on bridge-management decision-making are as follows:

  1. Adopt element-level bridge-inspection programs and establish standard condition states, quantities and recommended actions (maintenance, preservation, rehabilitation and replacement) to match the operational characteristics of the agency maintenance and/or preservation program;
  2. Establish national performance measures for all highway bridges for comparisons among bridge owners and owner-specific performance measures that can be used to allocate funding levels for a full range of actions (maintenance, preservation, rehabilitation and replacement) to optimize highway bridge conditions;
  3. Use owner-specific performance measures to set overall funding levels for maintenance and preservation programs;
  4. Determine bridge needs and a proposed multiyear treatment program based on owner-specific objectives and use the proposed program to develop a needs-based funding allocation, using all types of funding within the state’s prerogative, for each of the recommended action types (i.e., maintenance, preservation, rehabilitation and replacement);
  5. Establish standards for preventive-maintenance programs that are funded at levels set by analysis of performance measures. Programs must include the preservation needs of “cusp” bridges to keep them from becoming deficient bridges. In other words, do the right activity at the right time, keeping good bridges in good condition and moving away from the “worst first.” Experience in scan states has shown that preventive and minor maintenance must be a significant portion of bridge programs that optimize bridge conditions within limited budgets; and
  6. Develop work programs for maintenance and preservation at the lowest level of management or supervision when those positions are staffed by supervisors with extensive field maintenance knowledge and experience. Avoid blind use of work programs from bridge-management systems and work programs dictated by goals to maximize performance measures (although both bridge-management systems and performance measures provide useful information to maintenance crews).

Today, in light of the challenges facing the country’s highway bridge infrastructure, quality bridge-management decision-making is paramount. Bridge maintenance and preservation programs must be an integral part of any transportation asset management solution. Essential to the success of the bridge-management process is the identification of maintenance needs, performance measures, prioritization and verification. Bridge owner-agency support of the bridge-management process must be robust and provided at all levels of the organization.

Moreover, highway bridge programs must incorporate a significant focus on preventive maintenance and move away from a costly and unsustainable “worst-first” approach.

Bridge-management decision-making can succeed. It must succeed. Do we have any other choice?