The mean load method of the Canadian Highway Bridge Design Code is used to evaluate the shear and bending moment reliability of existing precast "type G" stringer bridges in Alberta that date from the late 1950s. The overall stringer population is categorized into distinct subpopulations using bridge-specific factors, including the degree of deterioration and approach span condition, which are readily identified during a brief field visit or from inspection reports. Critical sections to be investigated for reliability resisting shear forces or bending moments are determined. The reliability indices decrease if the reinforcement is corroded or the bridge approach is not smooth, and the reduction of the maximum axle loads permitted by legislation due to these factors is quantified. For bridge subpopulations where the actual reliability index is less than the target value for current legal axle loads, the critical axle load for moment is less than that for shear. Therefore, if flexural distress is not noted during inspection of such structures, they are likely adequate for the actual loading they are subjected to.Key words: corrosion, deterioration, dynamic load allowance, mean load method, reliability, visual inspection.