Guardrail phaj kem yog ib hom kab uas muaj zog, zoo hlau, zoo nkauj tsos, dav pom, yooj yim installation nrog corrosion kuj, siab kub tshav kub tsis kam, ci xim thiab ci siv lub sij hawm ntev, yuav tsum tau siv rau txoj kev loj, railway. , choj ntawm ob sab ntawm kev tiv thaiv