Whenever reports are issued on structures' conditions that identify deficient bridges, the numbers not only include structurally deficient bridges, but include those identified as functionally obsolete. Bridges are considered functionally obsolete if they have deck geometry, frequent flooding, clearance or approach roadway alignment that no longer meets the criteria for the system for which the bridge is a part.
Since a significant number of these structures are identified on the State system, and since SHA is constantly working to improve the overall system, we believe the time has come to not only continue efforts to eliminate all structurally deficient bridges, but to begin to identify, prioritize and perform construction efforts to reduce the number of functionally obsolete bridges that we believe affect traffic flow and safety and can be economically accomplished.
During Calendar Year 2005, SHA completed the first step in this effort, which was to identify all functionally obsolete bridges on our system, indicating the characteristics causing them to be functionally obsolete. During Calendar Year 2006, we completed our evaluation of the deficiencies that caused the structures to be functionally obsolete. We have broken down the deficiencies by categories; the results are shown below. (Some bridges are both functionally obsolete and structurally deficient; structures with both deficiencies are only listed under structurally deficient bridges.)
The number of structures on the functionally obsolete bridge list is 411 as of the 2007 submittal. There are no structurally deficient bridges included in this number.
Total Number of State Bridges = 2584
Note: Some structures are functionally obsolete in several categories. For charting purposes, they are only listed under one heading.
Total = 411
Deck Geometry - 244 bridges are FO in this Category
Under Geometry - Horizontal clearance 138 bridges are FO in this category
Under Geometry - Vertical clearance 12 bridges are FO in this category
Maximum Legal Height of Vehicle Including Load is 13'6''
FUNCTIONALLY OBSOLETE BRIDGES DUE TO APPROCH GEOMETRY
There are 16 structures which are FO in this category.
The structures in this category were rated functionally obsolete because approaching traffic needs to make driving adjustments (slow down,sharp turn, etc.) before crossing the bridge.
FUNCTIONALLY OBSOLETE BRIDGES DUE TO FLOODING
The one structure in this category is MD 12 over the Pocomoke River.
Clearly, inadequate bridge clear roadway width (lack of shoulders) is the major contributor to functionally obsolete bridges in Maryland. We identified those bridges where the bridge deck clear roadway was less than 24 feet and found 49 structures. Review of our photo inventory shows that the approach roadway section leading into and out of these bridges does not carry any shoulder either.
Now that we've narrowed the number down to 411 functionally obsolete bridges, we are gathering accident statistics to see whether or not any of these functionally obsolete structures are causing an extraordinary amount of accidents because of the deficiencies. It is not our intention to do any work on a functionally obsolete roadway width unless the structure is scheduled for work to improve its capacity. At that time, the functional obsolescence will be addressed as well. For deck replacements, we will add as much width as portions of the existing substructure and superstructure can tolerate.
Horizontal and vertical clearance inadequacies can usually only be handled by total replacements of the structure. This also includes lowering the roadway below, or raising the roadways above, which makes any efforts in this category highly unlikely unless there is a definite safety or traffic flow problem.