On-line, continuous monitoring technologies of a rigorous and objective nature are sought to quantitatively identify and evaluate the condition or health of highway structures over their useful lifetime. A global bridge evaluation methodology is under development based upon the structural identification concept, employing modal testing, truckload testing, and instrumented monitoring as its principal experimental tools. Test results are transformed to either modal flexibility or the unit influence line, which have been demonstrated to be conceptual, quantitative, comprehensive, and damage-sensitive signatures. Four test sites were tested, monitored, and studied in order to classify their similar bridge-type-specific behavior mechanisms and to validate the performance of the implemented methodology. Practical, type-specific procedures for instrumented monitoring and nondestructive evaluation can then be developed for the whole group or type of highway bridges.