(1) Level 1 load rating: A level 1 rating refers to any fully documented analysis or capacity evaluation that is signed and certified by a licensed professional engineer as being complete and correct in its computation of bridge load capacity. Generally, a level 1 analysis shall be in conformance with the analysis assumptions and provisions of the AASHTO Manual. However, evaluation methods and/or analysis assumptions that differ from the AASHTO provisions are permitted provided that they conform to accepted structural engineering practice, and they are fully documented and certified as being correct and appropriate by the certifying licensed professional engineer.

(2) Level 2 load rating: A level 2 load rating refers to a specific type of computerized load rating analysis produced by the department as part of its general bridge inspection program. However, any uncertified rating analysis that substantially conforms to the provisions and assumptions of the AASHTO Manual may be referred to as a level 2 load rating. Level 2 load ratings may be used to identify bridges that are likely to be load capacity deficient and must receive further evaluation. Level 2 ratings may be used to assign interim load restrictions to a deficient bridge until a level 1 load rating can be undertaken. The department's level 2 load ratings are computed using a department owned and maintained system of computer programs whose logic substantially conforms to analysis methods and assumptions contained in the AASHTO Manual. For each type of bridge capable of being analyzed, the level 2 programs contain some general assumptions relating to the location of critical components or cross sections to be analyzed. Although they are normally appropriate and generally accurate for typical situations they may not be correct in every case. Although quality control reviews are made, the department does not certify its level 2 ratings as being complete and fully correct in its computation of load capacity. The department maintains computer records of its level 2 data and analysis results, and updates this information on a periodic basis as part of its general inspection process.

(1) A level 1 load rating shall be performed as part of the structural design process for all new and replacement bridges and for all rehabilitation and repair designs involving a substantial structural alteration to the bridge. The level 1 load rating results for the new or reconstructed structure shall be summarized in a table placed on the contract drawings which are prepared for the project.

(2) A level 1 load rating shall be included as part of all Structural Integrity Evaluations as defined and required by Section 165.11 of this Code.

(3) A level 1 load rating shall be performed whenever the posted load on a bridge, or full legal load if the bridge is not posted, exceeds the operating rating capacity determined by a level 2 load rating.

(1) Load rating vehicles: all level 1 load ratings shall be based on both the AASHTO “HS” and “H” analysis vehicle configurations. Both the AASHTO “HS” and “H” truck loads and equivalent lane loads shall be used to determine the rating values. If the inventory rating as defined by the AASHTO manual based on the “HS” vehicle loading equals or exceeds HS-20 (36 tons), it is not necessary to compute ratings based on the “H” loading. Load ratings based on the AASHTO “Typical Legal Load Types” (Type 3, Type 3S2, Type 3-3) or any other rating vehicle configuration are not required by this Code, but may be desirable to use for individual posting evaluations.

(2) Rating summary sheet: all level 1 rating documentation shall contain a rating summary sheet, which provides the inventory and operating ratings, as such terms are defined in the AASHTO manual, for the bridge. The rating summary sheet shall also tabulate the ratings for each individual span or continuous span structural unit. For bridges which have structural floor systems, the ratings of the controlling floor system components as well as the main members shall be tabulated. Individual load rating values shall be expressed in terms of the equivalent rating vehicle and tonnage as shown: