Certain factors such as arcing between the contact wire and pantograph contact strip cause contact strips wear. Once local wear occurs, step-shaped wear patterns are highly likely developed. A contact strip with this step-shaped wear may lead to accidents such as contact wire breakage. To prevent such accidents, the authors have developed a method for detecting step-shaped wear on contact strips by measuring the vibration of the contact wire. This paper describes this new method and some results of experimental testing.