TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 398: Cathodic Protection for Life Extension of Existing Reinforced Concrete Bridge Elements examines the use of cathodic protection by state transportation agencies for controlling corrosion on existing reinforced concrete bridge elements. The report also explores the different types of cathodic protection systems, highlights case studies of states using these systems, and reviews reasons why public agencies may or may not employ cathodic protection.