Abstract: A method for on-site maintenance of a guardrail consisting of a continuous strip of metal section segments supported on posts at joints between adjacent segments, the guardrail is split at one of joints and the segments of one of the resulting two portions of the guardrail are detached successively from the posts and fed, still connected to adjacent segments, into an apparatus traveling along the strip and inside which the segments are subjected continuously to cleaning, metal facing and protective processes. Once processed, the segments come out successively from one end of the apparatus, as the latter travels along the guardrail, and are reconnected successively to the posts.