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Section 3: Sufficiency Ratings

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Calculation of Sufficiency Ratings

Sufficiency ratings are used by the Federal Highway Administration to select candidate bridges for the Highway Bridge Program. Sufficiency ratings are determined during the biennial bridge inspection and are intended to indicate a measure of the ability of a bridge to remain in service. Calculations for Sufficiency Ratings utilize a formula that includes various factors determined during the bridge field inspection and evaluation. The items considered below are those described in the instructions for the Coding Guide. Ratings are on a scale of 1 to 100, with 100 considered as an entirely sufficient bridge, usually new; an entirely deficient bridge would receive a rating of 0. Only bridges that carry vehicular traffic receive a Sufficiency Rating.A TxDOT interactive program is available to calculate Sufficiency Ratings and determine Structural Deficiency and Functional Obsolescence. The program is called BRISUF and it calculates the Sufficiency Rating based on data entered through an interactive prompt process. The Bridge Inspection Branch of the Bridge Division (BRG) should be contacted for assistance.

Whether using the prompted program BRISUF or hand calculations, the Sufficiency Rating (SR) is calculated by the equation:

  1. S1 is the Structural Adequacy and Safety (55 maximum, 0 minimum) calculated by the equation:
    1. A is the Reduction for Deterioration (not to exceed 55 or be less than 0) based on the lowest value of Item 59 (Superstructure Rating) or lowest value of Item 60 (Substructure Rating):
      • if < 2, then A = 55
      • if = 3, then A = 40
      • if = 4, then A = 25
      • if = 5, then A = 10
      • if > 6, then A = 0
      • if = N, then A = 0
    2. I is the Reduction for Load Capacity (not to exceed 55 or be less than 0) calculated by the equation and table:

      AIT is the Adjusted Inventory Tonnage, calculated by the following table of multipliers based on Item 66 (Inventory Rating):

      1st digit of Item 66 is...

      AIT = 2nd and 3rd digits of Item 66 multiplied by…

      1

      1.56

      2

      1.00

      3

      1.56

      4

      1.00

      5

      1.21

      6

      1.21

      9

      1.00



  2. S2 = the Serviceability and Functional Obsolescence (30 maximum, 0 minimum) calculated by the equation:
    1. J is a Rating Reduction (not to exceed 15) calculated by the following equation and tables: J = A + B + C + D + E + F

      If Item 58 (Deck Condition) is...

      If Item 67 (Structural Evaluation) is...

      If Item 68 (Deck Geometry) is...

      If Item 69 (Underclearances) is...

      If Item 71 (Waterway Adequacy) is...

      If Item 72 (Approach Roadway Alignment) is...

      ≤ 3, then A = 5

      ≤ 3, then B = 4

      ≤ 3, then C = 4

      ≤ 3, then D = 4

      ≤ 3, then E = 4

      ≤ 3, then F = 4

      = 4, then A = 3

      = 4, then B = 2

      = 4, then C = 2

      = 4, then D = 2

      = 4, then E = 2

      = 4, then F = 2

      = 5, then A = 1

      = 5, then B = 1

      = 5, then C = 1

      = 5, then D = 1

      = 5, then E = 1

      = 5, then F = 1

      ≥ 6, then A = 0

      ≥ 6, then B = 0

      ≥ 6, then C = 0

      ≥ 6, then D = 0

      ≥ 6, then E = 0

      ≥ 6, then F = 0

      = N, then A = 0

      = N, then B = 0

      = N, then C = 0

      = N, then D = 0

      = N, then E = 0

      = N, then F = 0



    2. (G + H ) is a Width of Roadway Insufficiency (not to exceed 15) calculated by the following relationships where the values for X and Y are first found by the following equations:

      Y = Item 51 (Roadway Width) ÷ First two digits of Item 28 (Lanes On)

      If Item 5.6 = 1, 2 or 8, then;

      X = Item 29 (Inventory Route ADT) ÷ First two digits of Item 28 (Lanes On)

      Then use the following conditions of (1), (2), or (3) to obtain the values for G and H:

      (1) For all bridges except culverts:

      (2) For one-lane bridges (including one-lane culverts:

      (3) For bridges with two or more lanes (including culverts):

      • If Item 43.4 (Culvert Type) is blank or 0 and;
      • If Item 51 (Roadway Width) + 2 ft < Item 32 (Approach Roadway Width), then G = 5.
      • If Item 51 (Roadway Width) + 2 ft ≥ Item 32 (Approach Roadway Width), then G = 0.
      • If the first two digits of Item 28 (Lanes On) = 01 and;
      • If Y < 14, then H = 15
      • If 14 < Y but < 18, then H = 3.75 (18 - Y).
      • If Y ≥ 18, then H = 0.
      • If the first two digits of Item 28 (Lanes On) = 02 and Y ≥ 16, then H = 0.
      • If the first two digits of Item 28 (Lanes On) = 03 and Y ≥ 15, then H = 0.
      • If the first two digits of Item 28 (Lanes On) = 04 and Y ≥ 14, then H = 0.
      • If the first two digits of Item 28 (Lanes On) = 05 and Y ≥ 12, then H = 0.

      If any one of the preceding conditions is met, do not continue trying to determine H because no lane width reductions are necessary. Otherwise, determine H based on the following values for X and Y:

      • If X ≤ 50 and Y < 9, then H = 7.5
      • If X ≤ 50 and Y ≥ 9, then H = 0.
      • If 50 < X ≤ 125 and Y < 10, then H = 15.
      • If 50 < X ≤ 125 and 10 ≤ Y < 13, then H = 5 (13 - Y)
      • If 50 < X ≤ 125 and Y ≥ 13, then H = 0
      • If 125 < X ≤ 375 and Y < 11, then H = 15
      • If 125 < X ≤ 375 and 11 ≤ Y < 14, then H = 5 (14 - Y)
      • If 125 < X ≤ 375 and Y ≥ 14, then H = 0
      • If 375 < X ≤ 1350 and Y < 12, then H = 15
      • If 375 < X ≤ 1350 and 12 ≤ Y < 16, then H = 3.75 (16 - Y)
      • If 375 < X ≤ 1350 and Y ≥ 16, then H = 0
      • If X > 1350 and Y < 15, then H = 15
      • If X > 1350 and 15 ≤ Y < 16, then H = 15 (16 - Y)
      • If X > 1350 and Y ≥ 16, then H = 0


    3. I is a Vertical Clearance Insufficiency (not to exceed 2) set by the following:

      If Item 100 (STRAHNET) > 0 and;

      Item 53 (Min Vert Clearance Over Bridge Deck) > 1600 then I = 0

      Item 53 (Min Vert Clearance Over Bridge Deck) < 1600 then I = 2

      If Item 100 (STRAHNET) = 0 and;

      Item 53 (Min Vert Clearance Over Bridge Deck) > 1400 then I = 0

      Item 53 (Min Vert Clearance Over Bridge Deck) < 1400 then I = 2

  3. S3 is the Essentiality for Public Use (not to exceed 15 or be less than 0) calculated by the equation:
    1. P is the portion for Public Use.

      First calculate K, which is a value based on the previously calculated S1 and S2:

      K = (S1 + S2) ÷ 85

      P = (Item 29* (ADT) x Item 19* (Detour Length) x 15) ÷ (200,000 x K)

      *If Item 5.1 = 1 use Item 29 (ADT) and Item 19 (Detour Length)

      *If Item 5.1 = 2 use Item 29A (Intersecting Route ADT) and Item 19A (Intersecting Route Detour Length)

    2. M is the portion for Military Use.

      If Item 100 (STRAHNET) > 0, then M = 2

      If Item 100 (STRAHNET) = 0, then M = 0

  4. S4 is a Special Reduction used only when S1 + S2 + S3 ≥ 50. Calculate S4 using the equation:
    1. R is a Detour Length Reduction (not to exceed 5) calculated by the equation:

      R = [Item 19* (Detour Length)]4 x (5.205 x 10-8)

      *If Item 5.1 = 1 use Item 19 (Detour Length)

      *If Item 5.1 = 2 use Item 19A (Intersecting Route Detour Length)

    2. S is a Structure Type Reduction set by the following:

      If the first digit of Item 43.1 (Main Span Type) is 7 or 8 or if the 2nd digit of Item 43.1 (Main Span Type) is 2, 3, 4, 5, 6, or 7, then S = 5.

      Otherwise, S = 0

    3. T is a Traffic Safety Feature reduction set by the following:

      If 2 digits of Item 36 (Traffic Safety Features) = 0, then T = 1

      If 3 digits of Item 36 (Traffic Safety Features) = 0, then T = 2

      If 4 digits of Item 36 (Traffic Safety Features) = 0, then T = 3


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